Update version

Fixes #123

.github/FUNDING.yml

@@ -1,3 +0,0 @@
-github: Tyrrrz
-patreon: Tyrrrz
-custom: ['buymeacoffee.com/Tyrrrz', 'tyrrrz.me/donate']

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -1,30 +1,42 @@
-name: "\U0001F41E Bug report"
+name: 🐞 Bug report
 description: Report broken functionality.
 labels: [bug]
+
 body:
 - type: markdown
   attributes:
     value: |
-      - Please check existing issues (both opened and closed) to ensure that this bug hasn't been reported before.
+      🧐 **Guidelines:**
-      - If you want to ask a question instead of reporting a bug, use [discussions](https://github.com/Tyrrrz/CliFx/discussions/new) instead.
+
+      - Search through [existing issues](https://github.com/Tyrrrz/CliFx/issues?q=is%3Aissue) first to ensure that this bug has not been reported before.
+      - Write a descriptive title for your issue. Avoid generic or vague titles such as "Something's not working" or "A couple of problems".
+      - Keep your issue focused on one single problem. If you have multiple bug reports, please create separate issues for each of them.
+      - Provide as much context as possible in the details section. Include screenshots, screen recordings, links, references, or anything else you may consider relevant.
+      - If you want to ask a question instead of reporting a bug, please use [discussions](https://github.com/Tyrrrz/CliFx/discussions/new) instead.
 
 - type: input
   attributes:
     label: Version
-    description: "Which version(s) of CliFx does this bug affect?"
+    description: Which version of CliFx does this bug affect?
+    placeholder: ver X.Y.Z
   validations:
     required: true
 
 - type: textarea
   attributes:
     label: Details
-    description: "Clear and thorough explanation of the bug. If relevant, include screenshots or screen recordings."
+    description: Clear and thorough explanation of the bug.
+    placeholder: I was doing X expecting Y to happen, but Z happened instead.
   validations:
     required: true
 
 - type: textarea
   attributes:
     label: Steps to reproduce
-    description: "Minimum steps or code required to reproduce the bug."
+    description: Minimum steps required to reproduce the bug.
+    placeholder: |
+      - Step 1
+      - Step 2
+      - Step 3
   validations:
     required: true

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,8 @@
 blank_issues_enabled: false
 contact_links:
-  - name: "\U0001F5E8 Ask a question"
+  - name: 💬 Discord server
+    url: https://discord.gg/2SUWKFnHSm
+    about: Chat with the project community.
+  - name: 🗨 Discussions
     url: https://github.com/Tyrrrz/CliFx/discussions/new
-    about: Please ask and answer questions here.  
+    about: Ask and answer questions.

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -1,16 +1,22 @@
-name: "\U00002728 Feature request"
+name: ✨ Feature request
 description: Request a new feature.
 labels: [enhancement]
+
 body:
 - type: markdown
   attributes:
     value: |
-      - Please check existing issues (both opened and closed) to ensure that this feature hasn't been requested before.
+      🧐 **Guidelines:**
-      - If you want to ask a question instead of requesting a feature, use [**discussions**](https://github.com/Tyrrrz/CliFx/discussions/new) instead.
+
+      - Search through [existing issues](https://github.com/Tyrrrz/CliFx/issues?q=is%3Aissue) first to ensure that this feature has not been requested before.
+      - Write a descriptive title for your issue. Avoid generic or vague titles such as "Some suggestions" or "Ideas for improvement".
+      - Keep your issue focused on one single problem. If you have multiple feature requests, please create separate issues for each of them.
+      - Provide as much context as possible in the details section. Include screenshots, screen recordings, links, references, or anything else you may consider relevant.
+      - If you want to ask a question instead of requesting a feature, please use [discussions](https://github.com/Tyrrrz/CliFx/discussions/new) instead.
 
 - type: textarea
   attributes:
     label: Details
-    description: "Clear and thorough explanation of the feature you have in mind."
+    description: Clear and thorough explanation of the feature you have in mind.
   validations:
     required: true

.github/workflows/CD.yml

@@ -1,25 +0,0 @@
-name: CD
-
-on:
-  push:
-    tags:
-      - "*"
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2.3.3
-
-      - name: Install .NET
-        uses: actions/setup-dotnet@v1.7.2
-        with:
-          dotnet-version: 5.0.x
-
-      - name: Pack
-        run: dotnet pack CliFx --configuration Release
-
-      - name: Deploy
-        run: dotnet nuget push CliFx/bin/Release/*.nupkg -s nuget.org -k ${{ secrets.NUGET_TOKEN }}

.github/workflows/CI.yml

@@ -1,28 +0,0 @@
-name: CI
-
-on: [push, pull_request]
-
-jobs:
-  build:
-    runs-on: ${{ matrix.os }}
-
-    strategy:
-      matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest]
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2.3.3
-
-      - name: Install .NET
-        uses: actions/setup-dotnet@v1.7.2
-        with:
-          dotnet-version: 5.0.x
-
-      - name: Build & test
-        run: dotnet test --configuration Release --logger GitHubActions
-
-      - name: Upload coverage
-        uses: codecov/codecov-action@v1.0.5
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }}

.github/workflows/main.yml

@@ -0,0 +1,11 @@
+name: main
+
+on: [push, pull_request]
+
+jobs:
+  main:
+    uses: Tyrrrz/.github/.github/workflows/NuGet.yml@master
+    secrets:
+      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+      NUGET_TOKEN: ${{ secrets.NUGET_TOKEN }}
+      DISCORD_WEBHOOK: ${{ secrets.DISCORD_WEBHOOK }}

Changelog.md

@@ -1,3 +1,32 @@
+### v2.2.2 (30-Jan-2022)
+
+- Fixed an issue where `ConsoleWriter` and `ConsoleReader` were not properly thread-safe.
+- Fixed an issue where the analyzer failed to load under certain circumstances when running inside Visual Studio.
+
+### v2.2.1 (16-Jan-2022)
+
+- Fixed an issue which caused help text to not show default values for optional parameters. (Thanks [@AliReZa Sabouri](https://github.com/alirezanet))
+
+### v2.2 (11-Jan-2022)
+
+- Added support for optional parameters. A parameter can be marked as optional by setting `IsRequired = false` on the attribute. Only one parameter is allowed to be optional and such parameter must be the last in order. (Thanks [@AliReZa Sabouri](https://github.com/alirezanet))
+- Fixed an issue where parameters and options bound to properties implemented as default interface members were not working correctly. (Thanks [@AliReZa Sabouri](https://github.com/alirezanet))
+
+### v2.1 (04-Jan-2022)
+
+- Added `IConsole.Clear()` with corresponding implementations in `SystemConsole`, `FakeConsole`, and `FakeInMemoryConsole`. (Thanks [@Alex Rosenfeld](https://github.com/alexrosenfeld10))
+- Added `IConsole.ReadKey()` with corresponding implementations in `SystemConsole`, `FakeConsole`, and `FakeInMemoryConsole`. (Thanks [@Alex Rosenfeld](https://github.com/alexrosenfeld10))
+- Fixed an issue that caused parameters to appear out of order in the usage format section of the help text. (Thanks [@David Fallah](https://github.com/TAGC))
+
+### v2.0.6 (17-Jul-2021)
+
+- Fixed an issue where an exception thrown via reflection during parameter or option binding resulted in `Exception has been thrown by the target of an invocation` error instead of a more useful message. Such exceptions will now be unwrapped to provide better user experience.
+
+### v2.0.5 (09-Jul-2021)
+
+- Fixed an issue where calling `IConsole.Output.Encoding.EncodingName` and some other members threw an exception.
+- Added readme file to the package.
+
 ### v2.0.4 (24-Apr-2021)
 
 - Fixed an issue where output and error streams in `SystemConsole` defaulted to UTF8 encoding with BOM when the application was running with UTF8 codepage. `ConsoleWriter` will now discard preamble from the specified encoding. This fix brings the behavior of `SystemConsole` in line with .NET's own `System.Console` which also discards preamble for output and error streams.
@@ -103,4 +132,4 @@ Please refer to the readme to find updated instructions and usage examples.
 
 - Changed `IConsole` interface (and as a result, `SystemConsole` and `VirtualConsole`) to support writing binary data. Instead of `TextReader`/`TextWriter` instances, the streams are now exposed as `StreamReader`/`StreamWriter` which provide the `BaseStream` property that allows raw access. Existing usages inside commands should remain the same because `StreamReader`/`StreamWriter` are compatible with their base classes `TextReader`/`TextWriter`, but if you were using `VirtualConsole` in tests, you may have to update it to the new API. Refer to the readme for more info.
 - Changed argument binding behavior so that an error is produced if the user provides an argument that doesn't match with any parameter or option. This is done in order to improve user experience, as otherwise the user may make a typo without knowing that their input wasn't taken into account.
-- Changed argument binding behavior so that options can be set to multiple argument values while specifying them with mixed naming. For example, `--option value1 -o value2 --option value3` would result in the option being set to corresponding three values, assuming `--option` and `-o` match with the same option.
+- Changed argument binding behavior so that options can be set to multiple argument values while specifying them with mixed naming. For example, `--option value1 -o value2 --option value3` would result in the option being set to corresponding three values, assuming `--option` and `-o` match with the same option.

CliFx.Analyzers.Tests/CliFx.Analyzers.Tests.csproj

@@ -1,9 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
-    <IsPackable>false</IsPackable>
-    <IsTestProject>true</IsTestProject>
     <CollectCoverage>true</CollectCoverage>
     <CoverletOutputFormat>opencover</CoverletOutputFormat>
   </PropertyGroup>
@@ -13,13 +11,14 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="Basic.Reference.Assemblies" Version="1.2.4" />
     <PackageReference Include="GitHubActionsTestLogger" Version="1.2.0" />
-    <PackageReference Include="FluentAssertions" Version="5.10.3" />
+    <PackageReference Include="FluentAssertions" Version="6.3.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.4.0" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" />
-    <PackageReference Include="xunit" Version="2.4.0" />
+    <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" PrivateAssets="all" />
-    <PackageReference Include="coverlet.msbuild" Version="3.0.3" PrivateAssets="all" />
+    <PackageReference Include="coverlet.msbuild" Version="3.1.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Analyzers.Tests/CommandMustBeAnnotatedAnalyzerSpecs.cs

@@ -2,71 +2,70 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class CommandMustBeAnnotatedAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustBeAnnotatedAnalyzer();
 
-        [Fact]
+public class CommandMustBeAnnotatedAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_a_command_is_not_annotated_with_the_command_attribute()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustBeAnnotatedAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_a_command_is_not_annotated_with_the_command_attribute()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_is_annotated_with_the_command_attribute()
+    public void Analyzer_does_not_report_an_error_if_a_command_is_annotated_with_the_command_attribute()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public abstract class MyCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_is_implemented_as_an_abstract_class()
+    public void Analyzer_does_not_report_an_error_if_a_command_is_implemented_as_an_abstract_class()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public abstract class MyCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
+    public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public class Foo
 {
     public int Bar { get; set; } = 5;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/CommandMustImplementInterfaceAnalyzerSpecs.cs

@@ -2,57 +2,56 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class CommandMustImplementInterfaceAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustImplementInterfaceAnalyzer();
 
-        [Fact]
+public class CommandMustImplementInterfaceAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_a_command_does_not_implement_ICommand_interface()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustImplementInterfaceAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_a_command_does_not_implement_ICommand_interface()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_implements_ICommand_interface()
+    public void Analyzer_does_not_report_an_error_if_a_command_implements_ICommand_interface()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
+    public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public class Foo
 {
     public int Bar { get; set; } = 5;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/GeneralSpecs.cs

@@ -4,28 +4,27 @@ using FluentAssertions;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
+
+public class GeneralSpecs
 {
-    public class GeneralSpecs
+    [Fact]
+    public void All_analyzers_have_unique_diagnostic_IDs()
     {
-        [Fact]
+        // Arrange
-        public void All_analyzers_have_unique_diagnostic_IDs()
+        var analyzers = typeof(AnalyzerBase)
-        {
+            .Assembly
-            // Arrange
+            .GetTypes()
-            var analyzers = typeof(AnalyzerBase)
+            .Where(t => !t.IsAbstract && t.IsAssignableTo(typeof(DiagnosticAnalyzer)))
-                .Assembly
+            .Select(t => (DiagnosticAnalyzer) Activator.CreateInstance(t)!)
-                .GetTypes()
+            .ToArray();
-                .Where(t => !t.IsAbstract && t.IsAssignableTo(typeof(DiagnosticAnalyzer)))
-                .Select(t => (DiagnosticAnalyzer) Activator.CreateInstance(t)!)
-                .ToArray();
 
-            // Act
+        // Act
-            var diagnosticIds = analyzers
+        var diagnosticIds = analyzers
-                .SelectMany(a => a.SupportedDiagnostics.Select(d => d.Id))
+            .SelectMany(a => a.SupportedDiagnostics.Select(d => d.Id))
-                .ToArray();
+            .ToArray();
 
-            // Assert
+        // Assert
-            diagnosticIds.Should().OnlyHaveUniqueItems();
+        diagnosticIds.Should().OnlyHaveUniqueItems();
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustBeInsideCommandAnalyzerSpecs.cs

@@ -2,34 +2,34 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustBeInsideCommandAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustBeInsideCommandAnalyzer();
 
-        [Fact]
+public class OptionMustBeInsideCommandAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_an_option_is_inside_a_class_that_is_not_a_command()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustBeInsideCommandAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_an_option_is_inside_a_class_that_is_not_a_command()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyClass
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_is_inside_a_command()
+    public void Analyzer_does_not_report_an_error_if_an_option_is_inside_a_command()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -39,32 +39,32 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_is_inside_an_abstract_class()
+    public void Analyzer_does_not_report_an_error_if_an_option_is_inside_an_abstract_class()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public abstract class MyCommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -73,8 +73,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveNameOrShortNameAnalyzerSpecs.cs

@@ -2,75 +2,75 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustHaveNameOrShortNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveNameOrShortNameAnalyzer();
 
-        [Fact]
+public class OptionMustHaveNameOrShortNameAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_an_option_does_not_have_a_name_or_short_name()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveNameOrShortNameAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_an_option_does_not_have_a_name_or_short_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(null)]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('f')]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -79,8 +79,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveUniqueNameAnalyzerSpecs.cs

@@ -2,81 +2,81 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustHaveUniqueNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueNameAnalyzer();
 
-        [Fact]
+public class OptionMustHaveUniqueNameAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_an_option_has_the_same_name_as_another_option()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueNameAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_an_option_has_the_same_name_as_another_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     [CommandOption(""foo"")]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     [CommandOption(""bar"")]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('f')]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -85,8 +85,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveUniqueShortNameAnalyzerSpecs.cs

@@ -2,103 +2,103 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustHaveUniqueShortNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueShortNameAnalyzer();
 
-        [Fact]
+public class OptionMustHaveUniqueShortNameAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_an_option_has_the_same_short_name_as_another_option()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueShortNameAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_an_option_has_the_same_short_name_as_another_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('f')]
     public string Foo { get; set; }
-    
+
     [CommandOption('f')]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_short_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_short_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('f')]
     public string Foo { get; set; }
-    
+
     [CommandOption('b')]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name_which_is_unique_only_in_casing()
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name_which_is_unique_only_in_casing()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('f')]
     public string Foo { get; set; }
-    
+
     [CommandOption('F')]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -107,8 +107,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidConverterAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustHaveValidConverterAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidConverterAnalyzer();
 
-        [Fact]
+public class OptionMustHaveValidConverterAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_the_specified_option_converter_does_not_derive_from_BindingConverter()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidConverterAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_the_specified_option_converter_does_not_derive_from_BindingConverter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyConverter
 {
     public string Convert(string rawValue) => rawValue;
@@ -24,20 +24,20 @@ public class MyCommand : ICommand
 {
     [CommandOption(""foo"", Converter = typeof(MyConverter))]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_the_specified_option_converter_derives_from_BindingConverter()
+    public void Analyzer_does_not_report_an_error_if_the_specified_option_converter_derives_from_BindingConverter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public class MyConverter : BindingConverter<string>
 {
     public override string Convert(string rawValue) => rawValue;
@@ -48,39 +48,39 @@ public class MyCommand : ICommand
 {
     [CommandOption(""foo"", Converter = typeof(MyConverter))]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_converter()
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_converter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidNameAnalyzerSpecs.cs

@@ -2,94 +2,94 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustHaveValidNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidNameAnalyzer();
 
-        [Fact]
+public class OptionMustHaveValidNameAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_an_option_has_a_name_which_is_too_short()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidNameAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_an_option_has_a_name_which_is_too_short()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""f"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_reports_an_error_if_an_option_has_a_name_that_starts_with_a_non_letter_character()
+    public void Analyzer_reports_an_error_if_an_option_has_a_name_that_starts_with_a_non_letter_character()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""1foo"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('f')]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -98,8 +98,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidShortNameAnalyzerSpecs.cs

@@ -2,75 +2,75 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustHaveValidShortNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidShortNameAnalyzer();
 
-        [Fact]
+public class OptionMustHaveValidShortNameAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_an_option_has_a_short_name_which_is_not_a_letter_character()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidShortNameAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_an_option_has_a_short_name_which_is_not_a_letter_character()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('1')]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_short_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_short_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption('f')]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -79,8 +79,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class OptionMustHaveValidValidatorsAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidValidatorsAnalyzer();
 
-        [Fact]
+public class OptionMustHaveValidValidatorsAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_one_of_the_specified_option_validators_does_not_derive_from_BindingValidator()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidValidatorsAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_one_of_the_specified_option_validators_does_not_derive_from_BindingValidator()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyValidator
 {
     public void Validate(string value) {}
@@ -24,20 +24,20 @@ public class MyCommand : ICommand
 {
     [CommandOption(""foo"", Validators = new[] {typeof(MyValidator)})]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_all_specified_option_validators_derive_from_BindingValidator()
+    public void Analyzer_does_not_report_an_error_if_all_specified_option_validators_derive_from_BindingValidator()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public class MyValidator : BindingValidator<string>
 {
     public override BindingValidationError Validate(string value) => Ok();
@@ -48,39 +48,39 @@ public class MyCommand : ICommand
 {
     [CommandOption(""foo"", Validators = new[] {typeof(MyValidator)})]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_validators()
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_validators()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandOption(""foo"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/ParameterMustBeInsideCommandAnalyzerSpecs.cs

@@ -2,34 +2,34 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class ParameterMustBeInsideCommandAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeInsideCommandAnalyzer();
 
-        [Fact]
+public class ParameterMustBeInsideCommandAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_a_parameter_is_inside_a_class_that_is_not_a_command()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeInsideCommandAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_a_parameter_is_inside_a_class_that_is_not_a_command()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyClass
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_is_inside_a_command()
+    public void Analyzer_does_not_report_an_error_if_a_parameter_is_inside_a_command()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -39,32 +39,32 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_is_inside_an_abstract_class()
+    public void Analyzer_does_not_report_an_error_if_a_parameter_is_inside_an_abstract_class()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public abstract class MyCommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -73,8 +73,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/ParameterMustBeLastIfNonRequiredAnalyzerSpecs.cs

@@ -0,0 +1,94 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+public class ParameterMustBeLastIfNonRequiredAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeLastIfNonRequiredAnalyzer();
+
+    [Fact]
+    public void Analyzer_reports_an_error_if_a_non_required_parameter_is_not_the_last_in_order()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Name = ""foo"", IsRequired = false)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, Name = ""bar"")]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_non_required_parameter_is_the_last_in_order()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Name = ""foo"")]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, Name = ""bar"", IsRequired = false)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_no_non_required_parameters_are_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Name = ""foo"")]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, Name = ""bar"", IsRequired = true)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+}

CliFx.Analyzers.Tests/ParameterMustBeLastIfNonScalarAnalyzerSpecs.cs

@@ -2,84 +2,84 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class ParameterMustBeLastIfNonScalarAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeLastIfNonScalarAnalyzer();
 
-        [Fact]
+public class ParameterMustBeLastIfNonScalarAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_a_non_scalar_parameter_is_not_last_in_order()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeLastIfNonScalarAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_a_non_scalar_parameter_is_not_the_last_in_order()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string[] Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_non_scalar_parameter_is_last_in_order()
+    public void Analyzer_does_not_report_an_error_if_a_non_scalar_parameter_is_the_last_in_order()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string[] Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
+    public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -88,8 +88,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/ParameterMustBeSingleIfNonRequiredAnalyzerSpecs.cs

@@ -0,0 +1,94 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+public class ParameterMustBeSingleIfNonRequiredAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeSingleIfNonRequiredAnalyzer();
+
+    [Fact]
+    public void Analyzer_reports_an_error_if_more_than_one_non_required_parameters_are_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, IsRequired = false)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, IsRequired = false)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_only_one_non_required_parameter_is_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, IsRequired = false)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_no_non_required_parameters_are_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, IsRequired = true)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+}

CliFx.Analyzers.Tests/ParameterMustBeSingleIfNonScalarAnalyzerSpecs.cs

@@ -2,84 +2,84 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class ParameterMustBeSingleIfNonScalarAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeSingleIfNonScalarAnalyzer();
 
-        [Fact]
+public class ParameterMustBeSingleIfNonScalarAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_more_than_one_non_scalar_parameters_are_defined()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeSingleIfNonScalarAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_more_than_one_non_scalar_parameters_are_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string[] Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string[] Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_only_one_non_scalar_parameter_is_defined()
+    public void Analyzer_does_not_report_an_error_if_only_one_non_scalar_parameter_is_defined()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string[] Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
+    public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -88,8 +88,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveUniqueNameAnalyzerSpecs.cs

@@ -2,62 +2,62 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class ParameterMustHaveUniqueNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueNameAnalyzer();
 
-        [Fact]
+public class ParameterMustHaveUniqueNameAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_a_parameter_has_the_same_name_as_another_parameter()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueNameAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_a_parameter_has_the_same_name_as_another_parameter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0, Name = ""foo"")]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1, Name = ""foo"")]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_name()
+    public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0, Name = ""foo"")]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1, Name = ""bar"")]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -66,8 +66,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveUniqueOrderAnalyzerSpecs.cs

@@ -2,62 +2,62 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class ParameterMustHaveUniqueOrderAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueOrderAnalyzer();
 
-        [Fact]
+public class ParameterMustHaveUniqueOrderAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_a_parameter_has_the_same_order_as_another_parameter()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueOrderAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_a_parameter_has_the_same_order_as_another_parameter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(0)]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_order()
+    public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_order()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -66,8 +66,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveValidConverterAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class ParameterMustHaveValidConverterAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidConverterAnalyzer();
 
-        [Fact]
+public class ParameterMustHaveValidConverterAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_the_specified_parameter_converter_does_not_derive_from_BindingConverter()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidConverterAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_the_specified_parameter_converter_does_not_derive_from_BindingConverter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyConverter
 {
     public string Convert(string rawValue) => rawValue;
@@ -24,20 +24,20 @@ public class MyCommand : ICommand
 {
     [CommandParameter(0, Converter = typeof(MyConverter))]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_the_specified_parameter_converter_derives_from_BindingConverter()
+    public void Analyzer_does_not_report_an_error_if_the_specified_parameter_converter_derives_from_BindingConverter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public class MyConverter : BindingConverter<string>
 {
     public override string Convert(string rawValue) => rawValue;
@@ -48,39 +48,39 @@ public class MyCommand : ICommand
 {
     [CommandParameter(0, Converter = typeof(MyConverter))]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_a_converter()
+    public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_a_converter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class ParameterMustHaveValidValidatorsAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidValidatorsAnalyzer();
 
-        [Fact]
+public class ParameterMustHaveValidValidatorsAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_one_of_the_specified_parameter_validators_does_not_derive_from_BindingValidator()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidValidatorsAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_one_of_the_specified_parameter_validators_does_not_derive_from_BindingValidator()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyValidator
 {
     public void Validate(string value) {}
@@ -24,20 +24,20 @@ public class MyCommand : ICommand
 {
     [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_all_specified_parameter_validators_derive_from_BindingValidator()
+    public void Analyzer_does_not_report_an_error_if_all_specified_parameter_validators_derive_from_BindingValidator()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 public class MyValidator : BindingValidator<string>
 {
     public override BindingValidationError Validate(string value) => Ok();
@@ -48,39 +48,39 @@ public class MyCommand : ICommand
 {
     [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_validators()
+    public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_validators()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_a_parameter()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/SystemConsoleShouldBeAvoidedAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
+namespace CliFx.Analyzers.Tests;
-{
-    public class SystemConsoleShouldBeAvoidedAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new SystemConsoleShouldBeAvoidedAnalyzer();
 
-        [Fact]
+public class SystemConsoleShouldBeAvoidedAnalyzerSpecs
-        public void Analyzer_reports_an_error_if_a_command_calls_a_method_on_SystemConsole()
+{
-        {
+    private static DiagnosticAnalyzer Analyzer { get; } = new SystemConsoleShouldBeAvoidedAnalyzer();
-            // Arrange
+
-            // language=cs
+    [Fact]
-            const string code = @"
+    public void Analyzer_reports_an_error_if_a_command_calls_a_method_on_SystemConsole()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -24,16 +24,16 @@ public class MyCommand : ICommand
     }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_reports_an_error_if_a_command_accesses_a_property_on_SystemConsole()
+    public void Analyzer_reports_an_error_if_a_command_accesses_a_property_on_SystemConsole()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -43,16 +43,16 @@ public class MyCommand : ICommand
         return default;
     }
 }";
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_reports_an_error_if_a_command_calls_a_method_on_a_property_of_SystemConsole()
+    public void Analyzer_reports_an_error_if_a_command_calls_a_method_on_a_property_of_SystemConsole()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -63,16 +63,16 @@ public class MyCommand : ICommand
     }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
+        Analyzer.Should().ProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_interacts_with_the_console_through_IConsole()
+    public void Analyzer_does_not_report_an_error_if_a_command_interacts_with_the_console_through_IConsole()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -83,16 +83,16 @@ public class MyCommand : ICommand
     }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_IConsole_is_not_available_in_the_current_method()
+    public void Analyzer_does_not_report_an_error_if_IConsole_is_not_available_in_the_current_method()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -101,16 +101,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_does_not_access_SystemConsole()
+    public void Analyzer_does_not_report_an_error_if_a_command_does_not_access_SystemConsole()
-        {
+    {
-            // Arrange
+        // Arrange
-            // language=cs
+        // language=cs
-            const string code = @"
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -120,8 +120,7 @@ public class MyCommand : ICommand
     }
 }";
 
-            // Act & assert
+        // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
+        Analyzer.Should().NotProduceDiagnostics(code);
-        }
     }
 }

CliFx.Analyzers.Tests/Utils/AnalyzerAssertions.cs

@@ -2,8 +2,8 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
-using System.Reflection;
 using System.Text;
+using Basic.Reference.Assemblies;
 using FluentAssertions.Execution;
 using FluentAssertions.Primitives;
 using Microsoft.CodeAnalysis;
@@ -11,164 +11,157 @@ using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Text;
 
-namespace CliFx.Analyzers.Tests.Utils
+namespace CliFx.Analyzers.Tests.Utils;
-{
-    internal class AnalyzerAssertions : ReferenceTypeAssertions<DiagnosticAnalyzer, AnalyzerAssertions>
-    {
-        protected override string Identifier { get; } = "analyzer";
 
-        public AnalyzerAssertions(DiagnosticAnalyzer analyzer)
+internal class AnalyzerAssertions : ReferenceTypeAssertions<DiagnosticAnalyzer, AnalyzerAssertions>
-            : base(analyzer)
+{
+    protected override string Identifier { get; } = "analyzer";
+
+    public AnalyzerAssertions(DiagnosticAnalyzer analyzer)
+        : base(analyzer)
+    {
+    }
+
+    private Compilation Compile(string sourceCode)
+    {
+        // Get default system namespaces
+        var defaultSystemNamespaces = new[]
         {
+            "System",
+            "System.Collections.Generic",
+            "System.Threading.Tasks"
+        };
+
+        // Get default CliFx namespaces
+        var defaultCliFxNamespaces = typeof(ICommand)
+            .Assembly
+            .GetTypes()
+            .Where(t => t.IsPublic)
+            .Select(t => t.Namespace)
+            .Distinct()
+            .ToArray();
+
+        // Append default imports to the source code
+        var sourceCodeWithUsings =
+            string.Join(Environment.NewLine, defaultSystemNamespaces.Select(n => $"using {n};")) +
+            string.Join(Environment.NewLine, defaultCliFxNamespaces.Select(n => $"using {n};")) +
+            Environment.NewLine +
+            sourceCode;
+
+        // Parse the source code
+        var ast = SyntaxFactory.ParseSyntaxTree(
+            SourceText.From(sourceCodeWithUsings),
+            CSharpParseOptions.Default
+        );
+
+        // Compile the code to IL
+        var compilation = CSharpCompilation.Create(
+            "CliFxTests_DynamicAssembly_" + Guid.NewGuid(),
+            new[] {ast},
+            ReferenceAssemblies.Net50
+                .Append(MetadataReference.CreateFromFile(typeof(ICommand).Assembly.Location)),
+            // DLL to avoid having to define the Main() method
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
+        );
+
+        var compilationErrors = compilation
+            .GetDiagnostics()
+            .Where(d => d.Severity >= DiagnosticSeverity.Error)
+            .ToArray();
+
+        if (compilationErrors.Any())
+        {
+            throw new InvalidOperationException(
+                "Failed to compile code." +
+                Environment.NewLine +
+                string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))
+            );
         }
 
-        private Compilation Compile(string sourceCode)
+        return compilation;
+    }
+
+    private IReadOnlyList<Diagnostic> GetProducedDiagnostics(string sourceCode)
+    {
+        var analyzers = ImmutableArray.Create(Subject);
+        var compilation = Compile(sourceCode);
+
+        return compilation
+            .WithAnalyzers(analyzers)
+            .GetAnalyzerDiagnosticsAsync(analyzers, default)
+            .GetAwaiter()
+            .GetResult();
+    }
+
+    public void ProduceDiagnostics(string sourceCode)
+    {
+        var expectedDiagnostics = Subject.SupportedDiagnostics;
+        var producedDiagnostics = GetProducedDiagnostics(sourceCode);
+
+        var expectedDiagnosticIds = expectedDiagnostics.Select(d => d.Id).Distinct().ToArray();
+        var producedDiagnosticIds = producedDiagnostics.Select(d => d.Id).Distinct().ToArray();
+
+        var result =
+            expectedDiagnosticIds.Intersect(producedDiagnosticIds).Count() ==
+            expectedDiagnosticIds.Length;
+
+        Execute.Assertion.ForCondition(result).FailWith(() =>
         {
-            // Get default system namespaces
+            var buffer = new StringBuilder();
-            var defaultSystemNamespaces = new[]
+
+            buffer.AppendLine("Expected and produced diagnostics do not match.");
+            buffer.AppendLine();
+
+            buffer.AppendLine("Expected diagnostics:");
+
+            foreach (var expectedDiagnostic in expectedDiagnostics)
             {
-                "System",
+                buffer.Append("  - ");
-                "System.Collections.Generic",
+                buffer.Append(expectedDiagnostic.Id);
-                "System.Threading.Tasks"
+                buffer.AppendLine();
-            };
-
-            // Get default CliFx namespaces
-            var defaultCliFxNamespaces = typeof(ICommand)
-                .Assembly
-                .GetTypes()
-                .Where(t => t.IsPublic)
-                .Select(t => t.Namespace)
-                .Distinct()
-                .ToArray();
-
-            // Append default imports to the source code
-            var sourceCodeWithUsings =
-                string.Join(Environment.NewLine, defaultSystemNamespaces.Select(n => $"using {n};")) +
-                string.Join(Environment.NewLine, defaultCliFxNamespaces.Select(n => $"using {n};")) +
-                Environment.NewLine +
-                sourceCode;
-
-            // Parse the source code
-            var ast = SyntaxFactory.ParseSyntaxTree(
-                SourceText.From(sourceCodeWithUsings),
-                CSharpParseOptions.Default
-            );
-
-            // Compile the code to IL
-            var compilation = CSharpCompilation.Create(
-                "CliFxTests_DynamicAssembly_" + Guid.NewGuid(),
-                new[] {ast},
-                new[]
-                {
-                    MetadataReference.CreateFromFile(Assembly.Load("netstandard").Location),
-                    MetadataReference.CreateFromFile(Assembly.Load("System.Runtime").Location),
-                    MetadataReference.CreateFromFile(typeof(object).Assembly.Location),
-                    MetadataReference.CreateFromFile(typeof(Console).Assembly.Location),
-                    MetadataReference.CreateFromFile(typeof(ICommand).Assembly.Location)
-                },
-                // DLL to avoid having to define the Main() method
-                new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
-            );
-
-            var compilationErrors = compilation
-                .GetDiagnostics()
-                .Where(d => d.Severity >= DiagnosticSeverity.Error)
-                .ToArray();
-
-            if (compilationErrors.Any())
-            {
-                throw new InvalidOperationException(
-                    "Failed to compile code." +
-                    Environment.NewLine +
-                    string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))
-                );
             }
 
-            return compilation;
+            buffer.AppendLine();
-        }
 
-        private IReadOnlyList<Diagnostic> GetProducedDiagnostics(string sourceCode)
+            buffer.AppendLine("Produced diagnostics:");
-        {
-            var analyzers = ImmutableArray.Create(Subject);
-            var compilation = Compile(sourceCode);
 
-            return compilation
+            foreach (var producedDiagnostic in producedDiagnostics)
-                .WithAnalyzers(analyzers)
-                .GetAnalyzerDiagnosticsAsync(analyzers, default)
-                .GetAwaiter()
-                .GetResult();
-        }
-
-        public void ProduceDiagnostics(string sourceCode)
-        {
-            var expectedDiagnostics = Subject.SupportedDiagnostics;
-            var producedDiagnostics = GetProducedDiagnostics(sourceCode);
-
-            var expectedDiagnosticIds = expectedDiagnostics.Select(d => d.Id).Distinct().ToArray();
-            var producedDiagnosticIds = producedDiagnostics.Select(d => d.Id).Distinct().ToArray();
-
-            var result =
-                expectedDiagnosticIds.Intersect(producedDiagnosticIds).Count() ==
-                expectedDiagnosticIds.Length;
-
-            Execute.Assertion.ForCondition(result).FailWith(() =>
             {
-                var buffer = new StringBuilder();
+                buffer.Append("  - ");
+                buffer.Append(producedDiagnostic);
+            }
 
-                buffer.AppendLine("Expected and produced diagnostics do not match.");
+            return new FailReason(buffer.ToString());
-                buffer.AppendLine();
+        });
-
-                buffer.AppendLine("Expected diagnostics:");
-
-                foreach (var expectedDiagnostic in expectedDiagnostics)
-                {
-                    buffer.Append("  - ");
-                    buffer.Append(expectedDiagnostic.Id);
-                    buffer.AppendLine();
-                }
-
-                buffer.AppendLine();
-
-                buffer.AppendLine("Produced diagnostics:");
-
-                foreach (var producedDiagnostic in producedDiagnostics)
-                {
-                    buffer.Append("  - ");
-                    buffer.Append(producedDiagnostic);
-                }
-
-                return new FailReason(buffer.ToString());
-            });
-        }
-
-        public void NotProduceDiagnostics(string sourceCode)
-        {
-            var producedDiagnostics = GetProducedDiagnostics(sourceCode);
-
-            var result = !producedDiagnostics.Any();
-
-            Execute.Assertion.ForCondition(result).FailWith(() =>
-            {
-                var buffer = new StringBuilder();
-
-                buffer.AppendLine("Expected no produced diagnostics.");
-                buffer.AppendLine();
-
-                buffer.AppendLine("Produced diagnostics:");
-
-                foreach (var producedDiagnostic in producedDiagnostics)
-                {
-                    buffer.Append("  - ");
-                    buffer.Append(producedDiagnostic);
-                }
-
-                return new FailReason(buffer.ToString());
-            });
-        }
     }
 
-    internal static class AnalyzerAssertionsExtensions
+    public void NotProduceDiagnostics(string sourceCode)
     {
-        public static AnalyzerAssertions Should(this DiagnosticAnalyzer analyzer) => new(analyzer);
+        var producedDiagnostics = GetProducedDiagnostics(sourceCode);
+
+        var result = !producedDiagnostics.Any();
+
+        Execute.Assertion.ForCondition(result).FailWith(() =>
+        {
+            var buffer = new StringBuilder();
+
+            buffer.AppendLine("Expected no produced diagnostics.");
+            buffer.AppendLine();
+
+            buffer.AppendLine("Produced diagnostics:");
+
+            foreach (var producedDiagnostic in producedDiagnostics)
+            {
+                buffer.Append("  - ");
+                buffer.Append(producedDiagnostic);
+            }
+
+            return new FailReason(buffer.ToString());
+        });
     }
+}
+
+internal static class AnalyzerAssertionsExtensions
+{
+    public static AnalyzerAssertions Should(this DiagnosticAnalyzer analyzer) => new(analyzer);
 }

CliFx.Analyzers/AnalyzerBase.cs

@@ -3,38 +3,37 @@ using CliFx.Analyzers.Utils.Extensions;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+public abstract class AnalyzerBase : DiagnosticAnalyzer
 {
-    public abstract class AnalyzerBase : DiagnosticAnalyzer
+    public DiagnosticDescriptor SupportedDiagnostic { get; }
+
+    public sealed override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; }
+
+    protected AnalyzerBase(
+        string diagnosticTitle,
+        string diagnosticMessage,
+        DiagnosticSeverity diagnosticSeverity = DiagnosticSeverity.Error)
     {
-        public DiagnosticDescriptor SupportedDiagnostic { get; }
+        SupportedDiagnostic = new DiagnosticDescriptor(
+            "CliFx_" + GetType().Name.TrimEnd("Analyzer"),
+            diagnosticTitle,
+            diagnosticMessage,
+            "CliFx",
+            diagnosticSeverity,
+            true
+        );
 
-        public sealed override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; }
+        SupportedDiagnostics = ImmutableArray.Create(SupportedDiagnostic);
+    }
 
-        protected AnalyzerBase(
+    protected Diagnostic CreateDiagnostic(Location location) =>
-            string diagnosticTitle,
+        Diagnostic.Create(SupportedDiagnostic, location);
-            string diagnosticMessage,
-            DiagnosticSeverity diagnosticSeverity = DiagnosticSeverity.Error)
-        {
-            SupportedDiagnostic = new DiagnosticDescriptor(
-                "CliFx_" + GetType().Name.TrimEnd("Analyzer"),
-                diagnosticTitle,
-                diagnosticMessage,
-                "CliFx",
-                diagnosticSeverity,
-                true
-            );
 
-            SupportedDiagnostics = ImmutableArray.Create(SupportedDiagnostic);
+    public override void Initialize(AnalysisContext context)
-        }
+    {
-
+        context.EnableConcurrentExecution();
-        protected Diagnostic CreateDiagnostic(Location location) =>
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
-            Diagnostic.Create(SupportedDiagnostic, location);
-
-        public override void Initialize(AnalysisContext context)
-        {
-            context.EnableConcurrentExecution();
-            context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
-        }
     }
 }

CliFx.Analyzers/CliFx.Analyzers.csproj

@@ -2,12 +2,13 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
     <Nullable>annotations</Nullable>
     <NoWarn>$(NoWarn);RS1025;RS1026</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.4.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" PrivateAssets="all" />
   </ItemGroup>
 
 </Project>

CliFx.Analyzers/CommandMustBeAnnotatedAnalyzer.cs

@@ -5,50 +5,49 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class CommandMustBeAnnotatedAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public CommandMustBeAnnotatedAnalyzer()
-    public class CommandMustBeAnnotatedAnalyzer : AnalyzerBase
+        : base(
+            $"Commands must be annotated with `{SymbolNames.CliFxCommandAttribute}`",
+            $"This type must be annotated with `{SymbolNames.CliFxCommandAttribute}` in order to be a valid command.")
     {
-        public CommandMustBeAnnotatedAnalyzer()
+    }
-            : base(
+
-                $"Commands must be annotated with `{SymbolNames.CliFxCommandAttribute}`",
+    private void Analyze(
-                $"This type must be annotated with `{SymbolNames.CliFxCommandAttribute}` in order to be a valid command.")
+        SyntaxNodeAnalysisContext context,
+        ClassDeclarationSyntax classDeclaration,
+        ITypeSymbol type)
+    {
+        // Ignore abstract classes, because they may be used to define
+        // base implementations for commands, in which case the command
+        // attribute doesn't make sense.
+        if (type.IsAbstract)
+            return;
+
+        var implementsCommandInterface = type
+            .AllInterfaces
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
+
+        var hasCommandAttribute = type
+            .GetAttributes()
+            .Select(a => a.AttributeClass)
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandAttribute));
+
+        // If the interface is implemented, but the attribute is missing,
+        // then it's very likely a user error.
+        if (implementsCommandInterface && !hasCommandAttribute)
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(classDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            ClassDeclarationSyntax classDeclaration,
-            ITypeSymbol type)
-        {
-            // Ignore abstract classes, because they may be used to define
-            // base implementations for commands, in which case the command
-            // attribute doesn't make sense.
-            if (type.IsAbstract)
-                return;
-
-            var implementsCommandInterface = type
-                .AllInterfaces
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
-
-            var hasCommandAttribute = type
-                .GetAttributes()
-                .Select(a => a.AttributeClass)
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandAttribute));
-
-            // If the interface is implemented, but the attribute is missing,
-            // then it's very likely a user error.
-            if (implementsCommandInterface && !hasCommandAttribute)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(classDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandleClassDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandleClassDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/CommandMustImplementInterfaceAnalyzer.cs

@@ -5,44 +5,43 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class CommandMustImplementInterfaceAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public CommandMustImplementInterfaceAnalyzer()
-    public class CommandMustImplementInterfaceAnalyzer : AnalyzerBase
+        : base(
+            $"Commands must implement `{SymbolNames.CliFxCommandInterface}` interface",
+            $"This type must implement `{SymbolNames.CliFxCommandInterface}` interface in order to be a valid command.")
     {
-        public CommandMustImplementInterfaceAnalyzer()
+    }
-            : base(
+
-                $"Commands must implement `{SymbolNames.CliFxCommandInterface}` interface",
+    private void Analyze(
-                $"This type must implement `{SymbolNames.CliFxCommandInterface}` interface in order to be a valid command.")
+        SyntaxNodeAnalysisContext context,
+        ClassDeclarationSyntax classDeclaration,
+        ITypeSymbol type)
+    {
+        var hasCommandAttribute = type
+            .GetAttributes()
+            .Select(a => a.AttributeClass)
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandAttribute));
+
+        var implementsCommandInterface = type
+            .AllInterfaces
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
+
+        // If the attribute is present, but the interface is not implemented,
+        // it's very likely a user error.
+        if (hasCommandAttribute && !implementsCommandInterface)
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(classDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            ClassDeclarationSyntax classDeclaration,
-            ITypeSymbol type)
-        {
-            var hasCommandAttribute = type
-                .GetAttributes()
-                .Select(a => a.AttributeClass)
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandAttribute));
-
-            var implementsCommandInterface = type
-                .AllInterfaces
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
-
-            // If the attribute is present, but the interface is not implemented,
-            // it's very likely a user error.
-            if (hasCommandAttribute && !implementsCommandInterface)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(classDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandleClassDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandleClassDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/ObjectModel/CommandOptionSymbol.cs

@@ -3,81 +3,79 @@ using Microsoft.CodeAnalysis;
 using System.Linq;
 using CliFx.Analyzers.Utils.Extensions;
 
-namespace CliFx.Analyzers.ObjectModel
+namespace CliFx.Analyzers.ObjectModel;
+
+internal partial class CommandOptionSymbol
 {
-    internal partial class CommandOptionSymbol
+    public string? Name { get; }
+
+    public char? ShortName { get; }
+
+    public ITypeSymbol? ConverterType { get; }
+
+    public IReadOnlyList<ITypeSymbol> ValidatorTypes { get; }
+
+    public CommandOptionSymbol(
+        string? name,
+        char? shortName,
+        ITypeSymbol? converterType,
+        IReadOnlyList<ITypeSymbol> validatorTypes)
     {
-        public string? Name { get; }
+        Name = name;
+        ShortName = shortName;
+        ConverterType = converterType;
+        ValidatorTypes = validatorTypes;
+    }
+}
 
-        public char? ShortName { get; }
+internal partial class CommandOptionSymbol
+{
+    private static AttributeData? TryGetOptionAttribute(IPropertySymbol property) =>
+        property
+            .GetAttributes()
+            .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandOptionAttribute));
 
-        public ITypeSymbol? ConverterType { get; }
+    private static CommandOptionSymbol FromAttribute(AttributeData attribute)
+    {
+        var name = attribute
+            .ConstructorArguments
+            .Where(a => a.Type.DisplayNameMatches("string") || a.Type.DisplayNameMatches("System.String"))
+            .Select(a => a.Value)
+            .FirstOrDefault() as string;
 
-        public IReadOnlyList<ITypeSymbol> ValidatorTypes { get; }
+        var shortName = attribute
+            .ConstructorArguments
+            .Where(a => a.Type.DisplayNameMatches("char") || a.Type.DisplayNameMatches("System.Char"))
+            .Select(a => a.Value)
+            .FirstOrDefault() as char?;
 
-        public CommandOptionSymbol(
+        var converter = attribute
-            string? name,
+            .NamedArguments
-            char? shortName,
+            .Where(a => a.Key == "Converter")
-            ITypeSymbol? converterType,
+            .Select(a => a.Value.Value)
-            IReadOnlyList<ITypeSymbol> validatorTypes)
+            .Cast<ITypeSymbol?>()
-        {
+            .FirstOrDefault();
-            Name = name;
+
-            ShortName = shortName;
+        var validators = attribute
-            ConverterType = converterType;
+            .NamedArguments
-            ValidatorTypes = validatorTypes;
+            .Where(a => a.Key == "Validators")
-        }
+            .SelectMany(a => a.Value.Values)
+            .Select(c => c.Value)
+            .Cast<ITypeSymbol>()
+            .ToArray();
+
+        return new CommandOptionSymbol(name, shortName, converter, validators);
     }
 
-    internal partial class CommandOptionSymbol
+    public static CommandOptionSymbol? TryResolve(IPropertySymbol property)
     {
-        private static AttributeData? TryGetOptionAttribute(IPropertySymbol property) =>
+        var attribute = TryGetOptionAttribute(property);
-            property
-                .GetAttributes()
-                .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandOptionAttribute));
 
-        private static CommandOptionSymbol FromAttribute(AttributeData attribute)
+        return attribute is not null
-        {
+            ? FromAttribute(attribute)
-            var name = attribute
+            : null;
-                .ConstructorArguments
-                .Where(a => a.Type.DisplayNameMatches("string") || a.Type.DisplayNameMatches("System.String"))
-                .Select(a => a.Value)
-                .FirstOrDefault() as string;
-
-            var shortName = attribute
-                .ConstructorArguments
-                .Where(a => a.Type.DisplayNameMatches("char") || a.Type.DisplayNameMatches("System.Char"))
-                .Select(a => a.Value)
-                .FirstOrDefault() as char?;
-
-            var converter = attribute
-                .NamedArguments
-                .Where(a => a.Key == "Converter")
-                .Select(a => a.Value.Value)
-                .Cast<ITypeSymbol?>()
-                .FirstOrDefault();
-
-            var validators = attribute
-                .NamedArguments
-                .Where(a => a.Key == "Validators")
-                .SelectMany(a => a.Value.Values)
-                .Select(c => c.Value)
-                .Cast<ITypeSymbol>()
-                .ToArray();
-
-            return new CommandOptionSymbol(name, shortName, converter, validators);
-        }
-
-        public static CommandOptionSymbol? TryResolve(IPropertySymbol property)
-        {
-            var attribute = TryGetOptionAttribute(property);
-
-            if (attribute is null)
-                return null;
-
-            return FromAttribute(attribute);
-        }
-
-        public static bool IsOptionProperty(IPropertySymbol property) =>
-            TryGetOptionAttribute(property) is not null;
     }
+
+    public static bool IsOptionProperty(IPropertySymbol property) =>
+        TryGetOptionAttribute(property) is not null;
 }

CliFx.Analyzers/ObjectModel/CommandParameterSymbol.cs

@@ -3,80 +3,88 @@ using System.Linq;
 using CliFx.Analyzers.Utils.Extensions;
 using Microsoft.CodeAnalysis;
 
-namespace CliFx.Analyzers.ObjectModel
+namespace CliFx.Analyzers.ObjectModel;
+
+internal partial class CommandParameterSymbol
 {
-    internal partial class CommandParameterSymbol
+    public int Order { get; }
+
+    public string? Name { get; }
+
+    public bool? IsRequired { get; }
+
+    public ITypeSymbol? ConverterType { get; }
+
+    public IReadOnlyList<ITypeSymbol> ValidatorTypes { get; }
+
+    public CommandParameterSymbol(
+        int order,
+        string? name,
+        bool? isRequired,
+        ITypeSymbol? converterType,
+        IReadOnlyList<ITypeSymbol> validatorTypes)
     {
-        public int Order { get; }
+        Order = order;
+        Name = name;
+        IsRequired = isRequired;
+        ConverterType = converterType;
+        ValidatorTypes = validatorTypes;
+    }
+}
 
-        public string? Name { get; }
+internal partial class CommandParameterSymbol
+{
+    private static AttributeData? TryGetParameterAttribute(IPropertySymbol property) =>
+        property
+            .GetAttributes()
+            .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandParameterAttribute));
 
-        public ITypeSymbol? ConverterType { get; }
+    private static CommandParameterSymbol FromAttribute(AttributeData attribute)
+    {
+        var order = (int)attribute
+            .ConstructorArguments
+            .Select(a => a.Value)
+            .First()!;
 
-        public IReadOnlyList<ITypeSymbol> ValidatorTypes { get; }
+        var name = attribute
+            .NamedArguments
+            .Where(a => a.Key == "Name")
+            .Select(a => a.Value.Value)
+            .FirstOrDefault() as string;
 
-        public CommandParameterSymbol(
+        var isRequired = attribute
-            int order,
+            .NamedArguments
-            string? name,
+            .Where(a => a.Key == "IsRequired")
-            ITypeSymbol? converterType,
+            .Select(a => a.Value.Value)
-            IReadOnlyList<ITypeSymbol> validatorTypes)
+            .FirstOrDefault() as bool?;
-        {
+
-            Order = order;
+        var converter = attribute
-            Name = name;
+            .NamedArguments
-            ConverterType = converterType;
+            .Where(a => a.Key == "Converter")
-            ValidatorTypes = validatorTypes;
+            .Select(a => a.Value.Value)
-        }
+            .Cast<ITypeSymbol?>()
+            .FirstOrDefault();
+
+        var validators = attribute
+            .NamedArguments
+            .Where(a => a.Key == "Validators")
+            .SelectMany(a => a.Value.Values)
+            .Select(c => c.Value)
+            .Cast<ITypeSymbol>()
+            .ToArray();
+
+        return new CommandParameterSymbol(order, name, isRequired, converter, validators);
     }
 
-    internal partial class CommandParameterSymbol
+    public static CommandParameterSymbol? TryResolve(IPropertySymbol property)
     {
-        private static AttributeData? TryGetParameterAttribute(IPropertySymbol property) =>
+        var attribute = TryGetParameterAttribute(property);
-            property
-                .GetAttributes()
-                .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandParameterAttribute));
 
-        private static CommandParameterSymbol FromAttribute(AttributeData attribute)
+        return attribute is not null
-        {
+            ? FromAttribute(attribute)
-            var order = (int) attribute
+            : null;
-                .ConstructorArguments
-                .Select(a => a.Value)
-                .First()!;
-
-            var name = attribute
-                .NamedArguments
-                .Where(a => a.Key == "Name")
-                .Select(a => a.Value.Value)
-                .FirstOrDefault() as string;
-
-            var converter = attribute
-                .NamedArguments
-                .Where(a => a.Key == "Converter")
-                .Select(a => a.Value.Value)
-                .Cast<ITypeSymbol?>()
-                .FirstOrDefault();
-
-            var validators = attribute
-                .NamedArguments
-                .Where(a => a.Key == "Validators")
-                .SelectMany(a => a.Value.Values)
-                .Select(c => c.Value)
-                .Cast<ITypeSymbol>()
-                .ToArray();
-
-            return new CommandParameterSymbol(order, name, converter, validators);
-        }
-
-        public static CommandParameterSymbol? TryResolve(IPropertySymbol property)
-        {
-            var attribute = TryGetParameterAttribute(property);
-
-            if (attribute is null)
-                return null;
-
-            return FromAttribute(attribute);
-        }
-
-        public static bool IsParameterProperty(IPropertySymbol property) =>
-            TryGetParameterAttribute(property) is not null;
     }
+
+    public static bool IsParameterProperty(IPropertySymbol property) =>
+        TryGetParameterAttribute(property) is not null;
 }

CliFx.Analyzers/ObjectModel/SymbolNames.cs

@@ -1,15 +1,14 @@
-namespace CliFx.Analyzers.ObjectModel
+namespace CliFx.Analyzers.ObjectModel;
+
+internal static class SymbolNames
 {
-    internal static class SymbolNames
+    public const string CliFxCommandInterface = "CliFx.ICommand";
-    {
+    public const string CliFxCommandAttribute = "CliFx.Attributes.CommandAttribute";
-        public const string CliFxCommandInterface = "CliFx.ICommand";
+    public const string CliFxCommandParameterAttribute = "CliFx.Attributes.CommandParameterAttribute";
-        public const string CliFxCommandAttribute = "CliFx.Attributes.CommandAttribute";
+    public const string CliFxCommandOptionAttribute = "CliFx.Attributes.CommandOptionAttribute";
-        public const string CliFxCommandParameterAttribute = "CliFx.Attributes.CommandParameterAttribute";
+    public const string CliFxConsoleInterface = "CliFx.Infrastructure.IConsole";
-        public const string CliFxCommandOptionAttribute = "CliFx.Attributes.CommandOptionAttribute";
+    public const string CliFxBindingConverterInterface = "CliFx.Extensibility.IBindingConverter";
-        public const string CliFxConsoleInterface = "CliFx.Infrastructure.IConsole";
+    public const string CliFxBindingConverterClass = "CliFx.Extensibility.BindingConverter<T>";
-        public const string CliFxBindingConverterInterface = "CliFx.Extensibility.IBindingConverter";
+    public const string CliFxBindingValidatorInterface = "CliFx.Extensibility.IBindingValidator";
-        public const string CliFxBindingConverterClass = "CliFx.Extensibility.BindingConverter<T>";
+    public const string CliFxBindingValidatorClass = "CliFx.Extensibility.BindingValidator<T>";
-        public const string CliFxBindingValidatorInterface = "CliFx.Extensibility.IBindingValidator";
-        public const string CliFxBindingValidatorClass = "CliFx.Extensibility.BindingValidator<T>";
-    }
 }

CliFx.Analyzers/OptionMustBeInsideCommandAnalyzer.cs

@@ -5,47 +5,46 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustBeInsideCommandAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustBeInsideCommandAnalyzer()
-    public class OptionMustBeInsideCommandAnalyzer : AnalyzerBase
+        : base(
+            "Options must be defined inside commands",
+            $"This option must be defined inside a class that implements `{SymbolNames.CliFxCommandInterface}`.")
     {
-        public OptionMustBeInsideCommandAnalyzer()
+    }
-            : base(
+
-                "Options must be defined inside commands",
+    private void Analyze(
-                $"This option must be defined inside a class that implements `{SymbolNames.CliFxCommandInterface}`.")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        if (property.ContainingType.IsAbstract)
+            return;
+
+        if (!CommandOptionSymbol.IsOptionProperty(property))
+            return;
+
+        var isInsideCommand = property
+            .ContainingType
+            .AllInterfaces
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
+
+        if (!isInsideCommand)
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
-
-            if (property.ContainingType.IsAbstract)
-                return;
-
-            if (!CommandOptionSymbol.IsOptionProperty(property))
-                return;
-
-            var isInsideCommand = property
-                .ContainingType
-                .AllInterfaces
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
-
-            if (!isInsideCommand)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/OptionMustHaveNameOrShortNameAnalyzer.cs

@@ -4,37 +4,36 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustHaveNameOrShortNameAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustHaveNameOrShortNameAnalyzer()
-    public class OptionMustHaveNameOrShortNameAnalyzer : AnalyzerBase
+        : base(
+            "Options must have either a name or short name specified",
+            "This option must have either a name or short name specified.")
     {
-        public OptionMustHaveNameOrShortNameAnalyzer()
+    }
-            : base(
-                "Options must have either a name or short name specified",
-                "This option must have either a name or short name specified.")
-        {
-        }
 
-        private void Analyze(
+    private void Analyze(
-            SyntaxNodeAnalysisContext context,
+        SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
+        PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
+        IPropertySymbol property)
-        {
+    {
-            var option = CommandOptionSymbol.TryResolve(property);
+        var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
+        if (option is null)
-                return;
+            return;
 
-            if (string.IsNullOrWhiteSpace(option.Name) && option.ShortName is null)
+        if (string.IsNullOrWhiteSpace(option.Name) && option.ShortName is null)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
         {
-            base.Initialize(context);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            context.HandlePropertyDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/OptionMustHaveUniqueNameAnalyzer.cs

@@ -6,60 +6,59 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustHaveUniqueNameAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustHaveUniqueNameAnalyzer()
-    public class OptionMustHaveUniqueNameAnalyzer : AnalyzerBase
+        : base(
+            "Options must have unique names",
+            "This option's name must be unique within the command (comparison IS NOT case sensitive).")
     {
-        public OptionMustHaveUniqueNameAnalyzer()
+    }
-            : base(
+
-                "Options must have unique names",
+    private void Analyze(
-                "This option's name must be unique within the command (comparison IS NOT case sensitive).")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            return;
+
+        if (string.IsNullOrWhiteSpace(option.Name))
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
         {
-        }
+            var otherOption = CommandOptionSymbol.TryResolve(otherProperty);
+            if (otherOption is null)
+                continue;
 
-        private void Analyze(
+            if (string.IsNullOrWhiteSpace(otherOption.Name))
-            SyntaxNodeAnalysisContext context,
+                continue;
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
 
-            var option = CommandOptionSymbol.TryResolve(property);
+            if (string.Equals(option.Name, otherOption.Name, StringComparison.OrdinalIgnoreCase))
-            if (option is null)
-                return;
-
-            if (string.IsNullOrWhiteSpace(option.Name))
-                return;
-
-            var otherProperties = property
-                .ContainingType
-                .GetMembers()
-                .OfType<IPropertySymbol>()
-                .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
-                .ToArray();
-
-            foreach (var otherProperty in otherProperties)
             {
-                var otherOption = CommandOptionSymbol.TryResolve(otherProperty);
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                if (otherOption is null)
-                    continue;
-
-                if (string.IsNullOrWhiteSpace(otherOption.Name))
-                    continue;
-
-                if (string.Equals(option.Name, otherOption.Name, StringComparison.OrdinalIgnoreCase))
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/OptionMustHaveUniqueShortNameAnalyzer.cs

@@ -5,60 +5,59 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustHaveUniqueShortNameAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustHaveUniqueShortNameAnalyzer()
-    public class OptionMustHaveUniqueShortNameAnalyzer : AnalyzerBase
+        : base(
+            "Options must have unique short names",
+            "This option's short name must be unique within the command (comparison IS case sensitive).")
     {
-        public OptionMustHaveUniqueShortNameAnalyzer()
+    }
-            : base(
+
-                "Options must have unique short names",
+    private void Analyze(
-                "This option's short name must be unique within the command (comparison IS case sensitive).")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            return;
+
+        if (option.ShortName is null)
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
         {
-        }
+            var otherOption = CommandOptionSymbol.TryResolve(otherProperty);
+            if (otherOption is null)
+                continue;
 
-        private void Analyze(
+            if (otherOption.ShortName is null)
-            SyntaxNodeAnalysisContext context,
+                continue;
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
 
-            var option = CommandOptionSymbol.TryResolve(property);
+            if (option.ShortName == otherOption.ShortName)
-            if (option is null)
-                return;
-
-            if (option.ShortName is null)
-                return;
-
-            var otherProperties = property
-                .ContainingType
-                .GetMembers()
-                .OfType<IPropertySymbol>()
-                .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
-                .ToArray();
-
-            foreach (var otherProperty in otherProperties)
             {
-                var otherOption = CommandOptionSymbol.TryResolve(otherProperty);
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                if (otherOption is null)
-                    continue;
-
-                if (otherOption.ShortName is null)
-                    continue;
-
-                if (option.ShortName == otherOption.ShortName)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/OptionMustHaveValidConverterAnalyzer.cs

@@ -5,46 +5,45 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustHaveValidConverterAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustHaveValidConverterAnalyzer()
-    public class OptionMustHaveValidConverterAnalyzer : AnalyzerBase
+        : base(
+            $"Option converters must derive from `{SymbolNames.CliFxBindingConverterClass}`",
+            $"Converter specified for this option must derive from `{SymbolNames.CliFxBindingConverterClass}`.")
     {
-        public OptionMustHaveValidConverterAnalyzer()
+    }
-            : base(
+
-                $"Option converters must derive from `{SymbolNames.CliFxBindingConverterClass}`",
+    private void Analyze(
-                $"Converter specified for this option must derive from `{SymbolNames.CliFxBindingConverterClass}`.")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            return;
+
+        if (option.ConverterType is null)
+            return;
+
+        // We check against an internal interface because checking against a generic class is a pain
+        var converterImplementsInterface = option
+            .ConverterType
+            .AllInterfaces
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingConverterInterface));
+
+        if (!converterImplementsInterface)
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
-                return;
-
-            if (option.ConverterType is null)
-                return;
-
-            // We check against an internal interface because checking against a generic class is a pain
-            var converterImplementsInterface = option
-                .ConverterType
-                .AllInterfaces
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingConverterInterface));
-
-            if (!converterImplementsInterface)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/OptionMustHaveValidNameAnalyzer.cs

@@ -4,40 +4,39 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustHaveValidNameAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustHaveValidNameAnalyzer()
-    public class OptionMustHaveValidNameAnalyzer : AnalyzerBase
+        : base(
+            "Options must have valid names",
+            "This option's name must be at least 2 characters long and must start with a letter.")
     {
-        public OptionMustHaveValidNameAnalyzer()
+    }
-            : base(
+
-                "Options must have valid names",
+    private void Analyze(
-                "This option's name must be at least 2 characters long and must start with a letter.")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            return;
+
+        if (string.IsNullOrWhiteSpace(option.Name))
+            return;
+
+        if (option.Name.Length < 2 || !char.IsLetter(option.Name[0]))
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
-                return;
-
-            if (string.IsNullOrWhiteSpace(option.Name))
-                return;
-
-            if (option.Name.Length < 2 || !char.IsLetter(option.Name[0]))
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/OptionMustHaveValidShortNameAnalyzer.cs

@@ -4,40 +4,39 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustHaveValidShortNameAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustHaveValidShortNameAnalyzer()
-    public class OptionMustHaveValidShortNameAnalyzer : AnalyzerBase
+        : base(
+            "Option short names must be letter characters",
+            "This option's short name must be a single letter character.")
     {
-        public OptionMustHaveValidShortNameAnalyzer()
+    }
-            : base(
+
-                "Option short names must be letter characters",
+    private void Analyze(
-                "This option's short name must be a single letter character.")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            return;
+
+        if (option.ShortName is null)
+            return;
+
+        if (!char.IsLetter(option.ShortName.Value))
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
-                return;
-
-            if (option.ShortName is null)
-                return;
-
-            if (!char.IsLetter(option.ShortName.Value))
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/OptionMustHaveValidValidatorsAnalyzer.cs

@@ -5,48 +5,47 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class OptionMustHaveValidValidatorsAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public OptionMustHaveValidValidatorsAnalyzer()
-    public class OptionMustHaveValidValidatorsAnalyzer : AnalyzerBase
+        : base(
+            $"Option validators must derive from `{SymbolNames.CliFxBindingValidatorClass}`",
+            $"All validators specified for this option must derive from `{SymbolNames.CliFxBindingValidatorClass}`.")
     {
-        public OptionMustHaveValidValidatorsAnalyzer()
+    }
-            : base(
-                $"Option validators must derive from `{SymbolNames.CliFxBindingValidatorClass}`",
-                $"All validators specified for this option must derive from `{SymbolNames.CliFxBindingValidatorClass}`.")
-        {
-        }
 
-        private void Analyze(
+    private void Analyze(
-            SyntaxNodeAnalysisContext context,
+        SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
+        PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
+        IPropertySymbol property)
-        {
+    {
-            var option = CommandOptionSymbol.TryResolve(property);
+        var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
+        if (option is null)
-                return;
+            return;
 
-            foreach (var validatorType in option.ValidatorTypes)
+        foreach (var validatorType in option.ValidatorTypes)
+        {
+            // We check against an internal interface because checking against a generic class is a pain
+            var validatorImplementsInterface = validatorType
+                .AllInterfaces
+                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingValidatorInterface));
+
+            if (!validatorImplementsInterface)
             {
-                // We check against an internal interface because checking against a generic class is a pain
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                var validatorImplementsInterface = validatorType
-                    .AllInterfaces
-                    .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingValidatorInterface));
 
-                if (!validatorImplementsInterface)
+                // No need to report multiple identical diagnostics on the same node
-                {
+                break;
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-                    // No need to report multiple identical diagnostics on the same node
-                    break;
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/ParameterMustBeInsideCommandAnalyzer.cs

@@ -5,47 +5,46 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustBeInsideCommandAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public ParameterMustBeInsideCommandAnalyzer()
-    public class ParameterMustBeInsideCommandAnalyzer : AnalyzerBase
+        : base(
+            "Parameters must be defined inside commands",
+            $"This parameter must be defined inside a class that implements `{SymbolNames.CliFxCommandInterface}`.")
     {
-        public ParameterMustBeInsideCommandAnalyzer()
+    }
-            : base(
+
-                "Parameters must be defined inside commands",
+    private void Analyze(
-                $"This parameter must be defined inside a class that implements `{SymbolNames.CliFxCommandInterface}`.")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        if (property.ContainingType.IsAbstract)
+            return;
+
+        if (!CommandParameterSymbol.IsParameterProperty(property))
+            return;
+
+        var isInsideCommand = property
+            .ContainingType
+            .AllInterfaces
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
+
+        if (!isInsideCommand)
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
-
-            if (property.ContainingType.IsAbstract)
-                return;
-
-            if (!CommandParameterSymbol.IsParameterProperty(property))
-                return;
-
-            var isInsideCommand = property
-                .ContainingType
-                .AllInterfaces
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
-
-            if (!isInsideCommand)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/ParameterMustBeLastIfNonRequiredAnalyzer.cs

@@ -0,0 +1,60 @@
+using System.Linq;
+using CliFx.Analyzers.ObjectModel;
+using CliFx.Analyzers.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustBeLastIfNonRequiredAnalyzer : AnalyzerBase
+{
+    public ParameterMustBeLastIfNonRequiredAnalyzer()
+        : base(
+            "Parameters marked as non-required must be the last in order",
+            "This parameter is non-required so it must be the last in order (its order must be highest within the command).")
+    {
+    }
+
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            return;
+
+        if (parameter.IsRequired != false)
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
+        {
+            var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+            if (otherParameter is null)
+                continue;
+
+            if (otherParameter.Order > parameter.Order)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustBeLastIfNonScalarAnalyzer.cs

@@ -5,64 +5,63 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustBeLastIfNonScalarAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public ParameterMustBeLastIfNonScalarAnalyzer()
-    public class ParameterMustBeLastIfNonScalarAnalyzer : AnalyzerBase
+        : base(
+            "Parameters of non-scalar types must be the last in order",
+            "This parameter has a non-scalar type so it must be the last in order (its order must be highest within the command).")
     {
-        public ParameterMustBeLastIfNonScalarAnalyzer()
+    }
-            : base(
+
-                "Parameters of non-scalar types must be last in order",
+    private static bool IsScalar(ITypeSymbol type) =>
-                "This parameter has a non-scalar type so it must be last in order (its order must be highest within the command).")
+        type.DisplayNameMatches("string") ||
+        type.DisplayNameMatches("System.String") ||
+        !type.AllInterfaces
+            .Select(i => i.ConstructedFrom)
+            .Any(s => s.DisplayNameMatches("System.Collections.Generic.IEnumerable<T>"));
+
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        if (IsScalar(property.Type))
+            return;
+
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
         {
-        }
+            var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+            if (otherParameter is null)
+                continue;
 
-        private static bool IsScalar(ITypeSymbol type) =>
+            if (otherParameter.Order > parameter.Order)
-            type.DisplayNameMatches("string") ||
-            type.DisplayNameMatches("System.String") ||
-            !type.AllInterfaces
-                .Select(i => i.ConstructedFrom)
-                .Any(s => s.DisplayNameMatches("System.Collections.Generic.IEnumerable<T>"));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
-
-            if (IsScalar(property.Type))
-                return;
-
-            var parameter = CommandParameterSymbol.TryResolve(property);
-            if (parameter is null)
-                return;
-
-            var otherProperties = property
-                .ContainingType
-                .GetMembers()
-                .OfType<IPropertySymbol>()
-                .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
-                .ToArray();
-
-            foreach (var otherProperty in otherProperties)
             {
-                var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                if (otherParameter is null)
-                    continue;
-
-                if (otherParameter.Order > parameter.Order)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/ParameterMustBeSingleIfNonRequiredAnalyzer.cs

@@ -0,0 +1,60 @@
+using System.Linq;
+using CliFx.Analyzers.ObjectModel;
+using CliFx.Analyzers.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustBeSingleIfNonRequiredAnalyzer : AnalyzerBase
+{
+    public ParameterMustBeSingleIfNonRequiredAnalyzer()
+        : base(
+            "Parameters marked as non-required are limited to one per command",
+            "This parameter is non-required so it must be the only such parameter in the command.")
+    {
+    }
+
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            return;
+
+        if (parameter.IsRequired != false)
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
+        {
+            var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+            if (otherParameter is null)
+                continue;
+
+            if (otherParameter.IsRequired == false)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustBeSingleIfNonScalarAnalyzer.cs

@@ -5,62 +5,61 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustBeSingleIfNonScalarAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public ParameterMustBeSingleIfNonScalarAnalyzer()
-    public class ParameterMustBeSingleIfNonScalarAnalyzer : AnalyzerBase
+        : base(
+            "Parameters of non-scalar types are limited to one per command",
+            "This parameter has a non-scalar type so it must be the only such parameter in the command.")
     {
-        public ParameterMustBeSingleIfNonScalarAnalyzer()
+    }
-            : base(
+
-                "Parameters of non-scalar types are limited to one per command",
+    private static bool IsScalar(ITypeSymbol type) =>
-                "This parameter has a non-scalar type so it must be the only such parameter in the command.")
+        type.DisplayNameMatches("string") ||
+        type.DisplayNameMatches("System.String") ||
+        !type.AllInterfaces
+            .Select(i => i.ConstructedFrom)
+            .Any(s => s.DisplayNameMatches("System.Collections.Generic.IEnumerable<T>"));
+
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        if (!CommandParameterSymbol.IsParameterProperty(property))
+            return;
+
+        if (IsScalar(property.Type))
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
         {
-        }
+            if (!CommandParameterSymbol.IsParameterProperty(otherProperty))
+                continue;
 
-        private static bool IsScalar(ITypeSymbol type) =>
+            if (!IsScalar(otherProperty.Type))
-            type.DisplayNameMatches("string") ||
-            type.DisplayNameMatches("System.String") ||
-            !type.AllInterfaces
-                .Select(i => i.ConstructedFrom)
-                .Any(s => s.DisplayNameMatches("System.Collections.Generic.IEnumerable<T>"));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
-
-            if (!CommandParameterSymbol.IsParameterProperty(property))
-                return;
-
-            if (IsScalar(property.Type))
-                return;
-
-            var otherProperties = property
-                .ContainingType
-                .GetMembers()
-                .OfType<IPropertySymbol>()
-                .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
-                .ToArray();
-
-            foreach (var otherProperty in otherProperties)
             {
-                if (!CommandParameterSymbol.IsParameterProperty(otherProperty))
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                    continue;
-
-                if (!IsScalar(otherProperty.Type))
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/ParameterMustHaveUniqueNameAnalyzer.cs

@@ -6,60 +6,59 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustHaveUniqueNameAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public ParameterMustHaveUniqueNameAnalyzer()
-    public class ParameterMustHaveUniqueNameAnalyzer : AnalyzerBase
+        : base(
+            "Parameters must have unique names",
+            "This parameter's name must be unique within the command (comparison IS NOT case sensitive).")
     {
-        public ParameterMustHaveUniqueNameAnalyzer()
+    }
-            : base(
+
-                "Parameters must have unique names",
+    private void Analyze(
-                "This parameter's name must be unique within the command (comparison IS NOT case sensitive).")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            return;
+
+        if (string.IsNullOrWhiteSpace(parameter.Name))
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
         {
-        }
+            var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+            if (otherParameter is null)
+                continue;
 
-        private void Analyze(
+            if (string.IsNullOrWhiteSpace(otherParameter.Name))
-            SyntaxNodeAnalysisContext context,
+                continue;
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
 
-            var parameter = CommandParameterSymbol.TryResolve(property);
+            if (string.Equals(parameter.Name, otherParameter.Name, StringComparison.OrdinalIgnoreCase))
-            if (parameter is null)
-                return;
-
-            if (string.IsNullOrWhiteSpace(parameter.Name))
-                return;
-
-            var otherProperties = property
-                .ContainingType
-                .GetMembers()
-                .OfType<IPropertySymbol>()
-                .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
-                .ToArray();
-
-            foreach (var otherProperty in otherProperties)
             {
-                var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                if (otherParameter is null)
-                    continue;
-
-                if (string.IsNullOrWhiteSpace(otherParameter.Name))
-                    continue;
-
-                if (string.Equals(parameter.Name, otherParameter.Name, StringComparison.OrdinalIgnoreCase))
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/ParameterMustHaveUniqueOrderAnalyzer.cs

@@ -5,54 +5,53 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustHaveUniqueOrderAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public ParameterMustHaveUniqueOrderAnalyzer()
-    public class ParameterMustHaveUniqueOrderAnalyzer : AnalyzerBase
+        : base(
+            "Parameters must have unique order",
+            "This parameter's order must be unique within the command.")
     {
-        public ParameterMustHaveUniqueOrderAnalyzer()
+    }
-            : base(
+
-                "Parameters must have unique order",
+    private void Analyze(
-                "This parameter's order must be unique within the command.")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            return;
+
+        var otherProperties = property
+            .ContainingType
+            .GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .ToArray();
+
+        foreach (var otherProperty in otherProperties)
         {
-        }
+            var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+            if (otherParameter is null)
+                continue;
 
-        private void Analyze(
+            if (parameter.Order == otherParameter.Order)
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            if (property.ContainingType is null)
-                return;
-
-            var parameter = CommandParameterSymbol.TryResolve(property);
-            if (parameter is null)
-                return;
-
-            var otherProperties = property
-                .ContainingType
-                .GetMembers()
-                .OfType<IPropertySymbol>()
-                .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
-                .ToArray();
-
-            foreach (var otherProperty in otherProperties)
             {
-                var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                if (otherParameter is null)
-                    continue;
-
-                if (parameter.Order == otherParameter.Order)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/ParameterMustHaveValidConverterAnalyzer.cs

@@ -5,46 +5,45 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustHaveValidConverterAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public ParameterMustHaveValidConverterAnalyzer()
-    public class ParameterMustHaveValidConverterAnalyzer : AnalyzerBase
+        : base(
+            $"Parameter converters must derive from `{SymbolNames.CliFxBindingConverterClass}`",
+            $"Converter specified for this parameter must derive from `{SymbolNames.CliFxBindingConverterClass}`.")
     {
-        public ParameterMustHaveValidConverterAnalyzer()
+    }
-            : base(
+
-                $"Parameter converters must derive from `{SymbolNames.CliFxBindingConverterClass}`",
+    private void Analyze(
-                $"Converter specified for this parameter must derive from `{SymbolNames.CliFxBindingConverterClass}`.")
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            return;
+
+        if (parameter.ConverterType is null)
+            return;
+
+        // We check against an internal interface because checking against a generic class is a pain
+        var converterImplementsInterface = parameter
+            .ConverterType
+            .AllInterfaces
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingConverterInterface));
+
+        if (!converterImplementsInterface)
         {
-        }
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var parameter = CommandParameterSymbol.TryResolve(property);
-            if (parameter is null)
-                return;
-
-            if (parameter.ConverterType is null)
-                return;
-
-            // We check against an internal interface because checking against a generic class is a pain
-            var converterImplementsInterface = parameter
-                .ConverterType
-                .AllInterfaces
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingConverterInterface));
-
-            if (!converterImplementsInterface)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/ParameterMustHaveValidValidatorsAnalyzer.cs

@@ -5,48 +5,47 @@ using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class ParameterMustHaveValidValidatorsAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public ParameterMustHaveValidValidatorsAnalyzer()
-    public class ParameterMustHaveValidValidatorsAnalyzer : AnalyzerBase
+        : base(
+            $"Parameter validators must derive from `{SymbolNames.CliFxBindingValidatorClass}`",
+            $"All validators specified for this parameter must derive from `{SymbolNames.CliFxBindingValidatorClass}`.")
     {
-        public ParameterMustHaveValidValidatorsAnalyzer()
+    }
-            : base(
-                $"Parameter validators must derive from `{SymbolNames.CliFxBindingValidatorClass}`",
-                $"All validators specified for this parameter must derive from `{SymbolNames.CliFxBindingValidatorClass}`.")
-        {
-        }
 
-        private void Analyze(
+    private void Analyze(
-            SyntaxNodeAnalysisContext context,
+        SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
+        PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
+        IPropertySymbol property)
-        {
+    {
-            var parameter = CommandParameterSymbol.TryResolve(property);
+        var parameter = CommandParameterSymbol.TryResolve(property);
-            if (parameter is null)
+        if (parameter is null)
-                return;
+            return;
 
-            foreach (var validatorType in parameter.ValidatorTypes)
+        foreach (var validatorType in parameter.ValidatorTypes)
+        {
+            // We check against an internal interface because checking against a generic class is a pain
+            var validatorImplementsInterface = validatorType
+                .AllInterfaces
+                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingValidatorInterface));
+
+            if (!validatorImplementsInterface)
             {
-                // We check against an internal interface because checking against a generic class is a pain
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                var validatorImplementsInterface = validatorType
-                    .AllInterfaces
-                    .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingValidatorInterface));
 
-                if (!validatorImplementsInterface)
+                // No need to report multiple identical diagnostics on the same node
-                {
+                break;
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-                    // No need to report multiple identical diagnostics on the same node
-                    break;
-                }
             }
         }
+    }
 
-        public override void Initialize(AnalysisContext context)
+    public override void Initialize(AnalysisContext context)
-        {
+    {
-            base.Initialize(context);
+        base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+        context.HandlePropertyDeclaration(Analyze);
-        }
     }
 }

CliFx.Analyzers/SystemConsoleShouldBeAvoidedAnalyzer.cs

@@ -6,73 +6,72 @@ using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers
+namespace CliFx.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class SystemConsoleShouldBeAvoidedAnalyzer : AnalyzerBase
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public SystemConsoleShouldBeAvoidedAnalyzer()
-    public class SystemConsoleShouldBeAvoidedAnalyzer : AnalyzerBase
+        : base(
+            $"Avoid calling `System.Console` where `{SymbolNames.CliFxConsoleInterface}` is available",
+            $"Use the provided `{SymbolNames.CliFxConsoleInterface}` abstraction instead of `System.Console` to ensure that the command can be tested in isolation.",
+            DiagnosticSeverity.Warning)
     {
-        public SystemConsoleShouldBeAvoidedAnalyzer()
+    }
-            : base(
-                $"Avoid calling `System.Console` where `{SymbolNames.CliFxConsoleInterface}` is available",
-                $"Use the provided `{SymbolNames.CliFxConsoleInterface}` abstraction instead of `System.Console` to ensure that the command can be tested in isolation.",
-                DiagnosticSeverity.Warning)
-        {
-        }
 
-        private MemberAccessExpressionSyntax? TryGetSystemConsoleMemberAccess(
+    private MemberAccessExpressionSyntax? TryGetSystemConsoleMemberAccess(
-            SyntaxNodeAnalysisContext context,
+        SyntaxNodeAnalysisContext context,
-            SyntaxNode node)
+        SyntaxNode node)
-        {
+    {
-            var currentNode = node;
+        var currentNode = node;
 
-            while (currentNode is MemberAccessExpressionSyntax memberAccess)
+        while (currentNode is MemberAccessExpressionSyntax memberAccess)
+        {
+            var member = context.SemanticModel.GetSymbolInfo(memberAccess).Symbol;
+
+            if (member?.ContainingType?.DisplayNameMatches("System.Console") == true)
             {
-                var member = context.SemanticModel.GetSymbolInfo(memberAccess).Symbol;
+                return memberAccess;
-
-                if (member?.ContainingType?.DisplayNameMatches("System.Console") == true)
-                {
-                    return memberAccess;
-                }
-
-                // Get inner expression, which may be another member access expression.
-                // Example: System.Console.Error
-                //          ~~~~~~~~~~~~~~          <- inner member access expression
-                //          --------------------    <- outer member access expression
-                currentNode = memberAccess.Expression;
             }
 
-            return null;
+            // Get inner expression, which may be another member access expression.
+            // Example: System.Console.Error
+            //          ~~~~~~~~~~~~~~          <- inner member access expression
+            //          --------------------    <- outer member access expression
+            currentNode = memberAccess.Expression;
         }
 
-        private void Analyze(SyntaxNodeAnalysisContext context)
+        return null;
+    }
+
+    private void Analyze(SyntaxNodeAnalysisContext context)
+    {
+        // Try to get a member access on System.Console in the current expression,
+        // or in any of its inner expressions.
+        var systemConsoleMemberAccess = TryGetSystemConsoleMemberAccess(context, context.Node);
+        if (systemConsoleMemberAccess is null)
+            return;
+
+        // Check if IConsole is available in scope as an alternative to System.Console
+        var isConsoleInterfaceAvailable = context
+            .Node
+            .Ancestors()
+            .OfType<MethodDeclarationSyntax>()
+            .SelectMany(m => m.ParameterList.Parameters)
+            .Select(p => p.Type)
+            .Select(t => context.SemanticModel.GetSymbolInfo(t).Symbol)
+            .Where(s => s is not null)
+            .Any(s => s.DisplayNameMatches(SymbolNames.CliFxConsoleInterface));
+
+        if (isConsoleInterfaceAvailable)
         {
-            // Try to get a member access on System.Console in the current expression,
+            context.ReportDiagnostic(CreateDiagnostic(systemConsoleMemberAccess.GetLocation()));
-            // or in any of its inner expressions.
-            var systemConsoleMemberAccess = TryGetSystemConsoleMemberAccess(context, context.Node);
-            if (systemConsoleMemberAccess is null)
-                return;
-
-            // Check if IConsole is available in scope as an alternative to System.Console
-            var isConsoleInterfaceAvailable = context
-                .Node
-                .Ancestors()
-                .OfType<MethodDeclarationSyntax>()
-                .SelectMany(m => m.ParameterList.Parameters)
-                .Select(p => p.Type)
-                .Select(t => context.SemanticModel.GetSymbolInfo(t).Symbol)
-                .Where(s => s is not null)
-                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxConsoleInterface));
-
-            if (isConsoleInterfaceAvailable)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(systemConsoleMemberAccess.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            base.Initialize(context);
-            context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.SimpleMemberAccessExpression);
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.SimpleMemberAccessExpression);
+    }
 }

CliFx.Analyzers/Utils/Extensions/RoslynExtensions.cs

@@ -4,50 +4,49 @@ using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 
-namespace CliFx.Analyzers.Utils.Extensions
+namespace CliFx.Analyzers.Utils.Extensions;
+
+internal static class RoslynExtensions
 {
-    internal static class RoslynExtensions
+    public static bool DisplayNameMatches(this ISymbol symbol, string name) =>
+        string.Equals(
+            // Fully qualified name, without `global::`
+            symbol.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat),
+            name,
+            StringComparison.Ordinal
+        );
+
+    public static void HandleClassDeclaration(
+        this AnalysisContext analysisContext,
+        Action<SyntaxNodeAnalysisContext, ClassDeclarationSyntax, ITypeSymbol> analyze)
     {
-        public static bool DisplayNameMatches(this ISymbol symbol, string name) =>
+        analysisContext.RegisterSyntaxNodeAction(ctx =>
-            string.Equals(
-                // Fully qualified name, without `global::`
-                symbol.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat),
-                name,
-                StringComparison.Ordinal
-            );
-
-        public static void HandleClassDeclaration(
-            this AnalysisContext analysisContext,
-            Action<SyntaxNodeAnalysisContext, ClassDeclarationSyntax, ITypeSymbol> analyze)
         {
-            analysisContext.RegisterSyntaxNodeAction(ctx =>
+            if (ctx.Node is not ClassDeclarationSyntax classDeclaration)
-            {
+                return;
-                if (ctx.Node is not ClassDeclarationSyntax classDeclaration)
-                    return;
 
-                var type = ctx.SemanticModel.GetDeclaredSymbol(classDeclaration);
+            var type = ctx.SemanticModel.GetDeclaredSymbol(classDeclaration);
-                if (type is null)
+            if (type is null)
-                    return;
+                return;
 
-                analyze(ctx, classDeclaration, type);
+            analyze(ctx, classDeclaration, type);
-            }, SyntaxKind.ClassDeclaration);
+        }, SyntaxKind.ClassDeclaration);
-        }
+    }
 
-        public static void HandlePropertyDeclaration(
+    public static void HandlePropertyDeclaration(
-            this AnalysisContext analysisContext,
+        this AnalysisContext analysisContext,
-            Action<SyntaxNodeAnalysisContext, PropertyDeclarationSyntax, IPropertySymbol> analyze)
+        Action<SyntaxNodeAnalysisContext, PropertyDeclarationSyntax, IPropertySymbol> analyze)
+    {
+        analysisContext.RegisterSyntaxNodeAction(ctx =>
         {
-            analysisContext.RegisterSyntaxNodeAction(ctx =>
+            if (ctx.Node is not PropertyDeclarationSyntax propertyDeclaration)
-            {
+                return;
-                if (ctx.Node is not PropertyDeclarationSyntax propertyDeclaration)
-                    return;
 
-                var property = ctx.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
+            var property = ctx.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
-                if (property is null)
+            if (property is null)
-                    return;
+                return;
 
-                analyze(ctx, propertyDeclaration, property);
+            analyze(ctx, propertyDeclaration, property);
-            }, SyntaxKind.PropertyDeclaration);
+        }, SyntaxKind.PropertyDeclaration);
-        }
     }
 }

CliFx.Analyzers/Utils/Extensions/StringExtensions.cs

@@ -1,18 +1,17 @@
 using System;
 
-namespace CliFx.Analyzers.Utils.Extensions
+namespace CliFx.Analyzers.Utils.Extensions;
-{
-    internal static class StringExtensions
-    {
-        public static string TrimEnd(
-            this string str,
-            string sub,
-            StringComparison comparison = StringComparison.Ordinal)
-        {
-            while (str.EndsWith(sub, comparison))
-                str = str.Substring(0, str.Length - sub.Length);
 
-            return str;
+internal static class StringExtensions
-        }
+{
+    public static string TrimEnd(
+        this string str,
+        string sub,
+        StringComparison comparison = StringComparison.Ordinal)
+    {
+        while (str.EndsWith(sub, comparison))
+            str = str.Substring(0, str.Length - sub.Length);
+
+        return str;
     }
 }

CliFx.Benchmarks/Benchmarks.CliFx.cs

@@ -4,30 +4,29 @@ using BenchmarkDotNet.Attributes;
 using CliFx.Attributes;
 using CliFx.Infrastructure;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
-    public partial class Benchmarks
+    [Command]
+    public class CliFxCommand : ICommand
     {
-        [Command]
+        [CommandOption("str", 's')]
-        public class CliFxCommand : ICommand
+        public string? StrOption { get; set; }
-        {
-            [CommandOption("str", 's')]
-            public string? StrOption { get; set; }
 
-            [CommandOption("int", 'i')]
+        [CommandOption("int", 'i')]
-            public int IntOption { get; set; }
+        public int IntOption { get; set; }
 
-            [CommandOption("bool", 'b')]
+        [CommandOption("bool", 'b')]
-            public bool BoolOption { get; set; }
+        public bool BoolOption { get; set; }
 
-            public ValueTask ExecuteAsync(IConsole console) => default;
+        public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Benchmark(Description = "CliFx", Baseline = true)]
-        public async ValueTask<int> ExecuteWithCliFx() =>
-            await new CliApplicationBuilder()
-                .AddCommand<CliFxCommand>()
-                .Build()
-                .RunAsync(Arguments, new Dictionary<string, string>());
     }
+
+    [Benchmark(Description = "CliFx", Baseline = true)]
+    public async ValueTask<int> ExecuteWithCliFx() =>
+        await new CliApplicationBuilder()
+            .AddCommand<CliFxCommand>()
+            .Build()
+            .RunAsync(Arguments, new Dictionary<string, string>());
 }

CliFx.Benchmarks/Benchmarks.Clipr.cs

@@ -1,27 +1,26 @@
 using BenchmarkDotNet.Attributes;
 using clipr;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
-    public partial class Benchmarks
+    public class CliprCommand
     {
-        public class CliprCommand
+        [NamedArgument('s', "str")]
+        public string? StrOption { get; set; }
+
+        [NamedArgument('i', "int")]
+        public int IntOption { get; set; }
+
+        [NamedArgument('b', "bool", Constraint = NumArgsConstraint.Optional, Const = true)]
+        public bool BoolOption { get; set; }
+
+        public void Execute()
         {
-            [NamedArgument('s', "str")]
-            public string? StrOption { get; set; }
-
-            [NamedArgument('i', "int")]
-            public int IntOption { get; set; }
-
-            [NamedArgument('b', "bool", Constraint = NumArgsConstraint.Optional, Const = true)]
-            public bool BoolOption { get; set; }
-
-            public void Execute()
-            {
-            }
         }
-
-        [Benchmark(Description = "Clipr")]
-        public void ExecuteWithClipr() => CliParser.Parse<CliprCommand>(Arguments).Execute();
     }
+
+    [Benchmark(Description = "Clipr")]
+    public void ExecuteWithClipr() => CliParser.Parse<CliprCommand>(Arguments).Execute();
 }

CliFx.Benchmarks/Benchmarks.Cocona.cs

@@ -1,24 +1,23 @@
 using BenchmarkDotNet.Attributes;
 using Cocona;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
-{
-    public partial class Benchmarks
-    {
-        public class CoconaCommand
-        {
-            public void Execute(
-                [Option("str", new []{'s'})]
-                string? strOption,
-                [Option("int", new []{'i'})]
-                int intOption,
-                [Option("bool", new []{'b'})]
-                bool boolOption)
-            {
-            }
-        }
 
-        [Benchmark(Description = "Cocona")]
+public partial class Benchmarks
-        public void ExecuteWithCocona() => CoconaApp.Run<CoconaCommand>(Arguments);
+{
+    public class CoconaCommand
+    {
+        public void Execute(
+            [Option("str", new []{'s'})]
+            string? strOption,
+            [Option("int", new []{'i'})]
+            int intOption,
+            [Option("bool", new []{'b'})]
+            bool boolOption)
+        {
+        }
     }
+
+    [Benchmark(Description = "Cocona")]
+    public void ExecuteWithCocona() => CoconaApp.Run<CoconaCommand>(Arguments);
 }

CliFx.Benchmarks/Benchmarks.CommandLineParser.cs

@@ -1,30 +1,29 @@
 using BenchmarkDotNet.Attributes;
 using CommandLine;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
-    public partial class Benchmarks
+    public class CommandLineParserCommand
     {
-        public class CommandLineParserCommand
+        [Option('s', "str")]
+        public string? StrOption { get; set; }
+
+        [Option('i', "int")]
+        public int IntOption { get; set; }
+
+        [Option('b', "bool")]
+        public bool BoolOption { get; set; }
+
+        public void Execute()
         {
-            [Option('s', "str")]
-            public string? StrOption { get; set; }
-
-            [Option('i', "int")]
-            public int IntOption { get; set; }
-
-            [Option('b', "bool")]
-            public bool BoolOption { get; set; }
-
-            public void Execute()
-            {
-            }
         }
-
-        [Benchmark(Description = "CommandLineParser")]
-        public void ExecuteWithCommandLineParser() =>
-            new Parser()
-                .ParseArguments(Arguments, typeof(CommandLineParserCommand))
-                .WithParsed<CommandLineParserCommand>(c => c.Execute());
     }
+
+    [Benchmark(Description = "CommandLineParser")]
+    public void ExecuteWithCommandLineParser() =>
+        new Parser()
+            .ParseArguments(Arguments, typeof(CommandLineParserCommand))
+            .WithParsed<CommandLineParserCommand>(c => c.Execute());
 }

CliFx.Benchmarks/Benchmarks.McMaster.cs

@@ -1,25 +1,24 @@
 using BenchmarkDotNet.Attributes;
 using McMaster.Extensions.CommandLineUtils;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
-    public partial class Benchmarks
+    public class McMasterCommand
     {
-        public class McMasterCommand
+        [Option("--str|-s")]
-        {
+        public string? StrOption { get; set; }
-            [Option("--str|-s")]
-            public string? StrOption { get; set; }
 
-            [Option("--int|-i")]
+        [Option("--int|-i")]
-            public int IntOption { get; set; }
+        public int IntOption { get; set; }
 
-            [Option("--bool|-b")]
+        [Option("--bool|-b")]
-            public bool BoolOption { get; set; }
+        public bool BoolOption { get; set; }
 
-            public int OnExecute() => 0;
+        public int OnExecute() => 0;
-        }
-
-        [Benchmark(Description = "McMaster.Extensions.CommandLineUtils")]
-        public int ExecuteWithMcMaster() => CommandLineApplication.Execute<McMasterCommand>(Arguments);
     }
+
+    [Benchmark(Description = "McMaster.Extensions.CommandLineUtils")]
+    public int ExecuteWithMcMaster() => CommandLineApplication.Execute<McMasterCommand>(Arguments);
 }

CliFx.Benchmarks/Benchmarks.PowerArgs.cs

@@ -1,27 +1,26 @@
 using BenchmarkDotNet.Attributes;
 using PowerArgs;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
-    public partial class Benchmarks
+    public class PowerArgsCommand
     {
-        public class PowerArgsCommand
+        [ArgShortcut("--str"), ArgShortcut("-s")]
+        public string? StrOption { get; set; }
+
+        [ArgShortcut("--int"), ArgShortcut("-i")]
+        public int IntOption { get; set; }
+
+        [ArgShortcut("--bool"), ArgShortcut("-b")]
+        public bool BoolOption { get; set; }
+
+        public void Main()
         {
-            [ArgShortcut("--str"), ArgShortcut("-s")]
-            public string? StrOption { get; set; }
-
-            [ArgShortcut("--int"), ArgShortcut("-i")]
-            public int IntOption { get; set; }
-
-            [ArgShortcut("--bool"), ArgShortcut("-b")]
-            public bool BoolOption { get; set; }
-
-            public void Main()
-            {
-            }
         }
-
-        [Benchmark(Description = "PowerArgs")]
-        public void ExecuteWithPowerArgs() => Args.InvokeMain<PowerArgsCommand>(Arguments);
     }
+
+    [Benchmark(Description = "PowerArgs")]
+    public void ExecuteWithPowerArgs() => Args.InvokeMain<PowerArgsCommand>(Arguments);
 }

CliFx.Benchmarks/Benchmarks.SystemCommandLine.cs

@@ -3,42 +3,41 @@ using System.CommandLine.Invocation;
 using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
-    public partial class Benchmarks
+    public class SystemCommandLineCommand
     {
-        public class SystemCommandLineCommand
+        public static int ExecuteHandler(string s, int i, bool b) => 0;
+
+        public Task<int> ExecuteAsync(string[] args)
         {
-            public static int ExecuteHandler(string s, int i, bool b) => 0;
+            var command = new RootCommand
-
-            public Task<int> ExecuteAsync(string[] args)
             {
-                var command = new RootCommand
+                new Option(new[] {"--str", "-s"})
                 {
-                    new Option(new[] {"--str", "-s"})
+                    Argument = new Argument<string?>()
-                    {
+                },
-                        Argument = new Argument<string?>()
+                new Option(new[] {"--int", "-i"})
-                    },
+                {
-                    new Option(new[] {"--int", "-i"})
+                    Argument = new Argument<int>()
-                    {
+                },
-                        Argument = new Argument<int>()
+                new Option(new[] {"--bool", "-b"})
-                    },
+                {
-                    new Option(new[] {"--bool", "-b"})
+                    Argument = new Argument<bool>()
-                    {
+                }
-                        Argument = new Argument<bool>()
+            };
-                    }
-                };
 
-                command.Handler = CommandHandler.Create(
+            command.Handler = CommandHandler.Create(
-                    typeof(SystemCommandLineCommand).GetMethod(nameof(ExecuteHandler))!
+                typeof(SystemCommandLineCommand).GetMethod(nameof(ExecuteHandler))!
-                );
+            );
 
-                return command.InvokeAsync(args);
+            return command.InvokeAsync(args);
-            }
         }
-
-        [Benchmark(Description = "System.CommandLine")]
-        public async Task<int> ExecuteWithSystemCommandLine() =>
-            await new SystemCommandLineCommand().ExecuteAsync(Arguments);
     }
+
+    [Benchmark(Description = "System.CommandLine")]
+    public async Task<int> ExecuteWithSystemCommandLine() =>
+        await new SystemCommandLineCommand().ExecuteAsync(Arguments);
 }

CliFx.Benchmarks/Benchmarks.cs

@@ -3,18 +3,17 @@ using BenchmarkDotNet.Configs;
 using BenchmarkDotNet.Order;
 using BenchmarkDotNet.Running;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
-{
-    [RankColumn]
-    [Orderer(SummaryOrderPolicy.FastestToSlowest)]
-    public partial class Benchmarks
-    {
-        private static readonly string[] Arguments = {"--str", "hello world", "-i", "13", "-b"};
 
-        public static void Main() => BenchmarkRunner.Run<Benchmarks>(
+[RankColumn]
-            DefaultConfig
+[Orderer(SummaryOrderPolicy.FastestToSlowest)]
-                .Instance
+public partial class Benchmarks
-                .With(ConfigOptions.DisableOptimizationsValidator)
+{
-        );
+    private static readonly string[] Arguments = {"--str", "hello world", "-i", "13", "-b"};
-    }
+
+    public static void Main() => BenchmarkRunner.Run<Benchmarks>(
+        DefaultConfig
+            .Instance
+            .WithOptions(ConfigOptions.DisableOptimizationsValidator)
+    );
 }

CliFx.Benchmarks/CliFx.Benchmarks.csproj

@@ -2,15 +2,15 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.12.1" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.13.1" />
     <PackageReference Include="clipr" Version="1.6.1" />
-    <PackageReference Include="Cocona" Version="1.5.0" />
+    <PackageReference Include="Cocona" Version="1.6.0" />
     <PackageReference Include="CommandLineParser" Version="2.8.0" />
-    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="3.1.0" />
+    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="4.0.0" />
     <PackageReference Include="PowerArgs" Version="3.6.0" />
     <PackageReference Include="System.CommandLine" Version="2.0.0-beta1.20574.7" />
   </ItemGroup>

CliFx.Demo/CliFx.Demo.csproj

@@ -2,11 +2,11 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="5.0.1" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
   </ItemGroup>
 

CliFx.Demo/Commands/BookAddCommand.cs

@@ -6,65 +6,64 @@ using CliFx.Demo.Utils;
 using CliFx.Exceptions;
 using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book add", Description = "Add a book to the library.")]
+public partial class BookAddCommand : ICommand
 {
-    [Command("book add", Description = "Add a book to the library.")]
+    private readonly LibraryProvider _libraryProvider;
-    public partial class BookAddCommand : ICommand
+
+    [CommandParameter(0, Name = "title", Description = "Book title.")]
+    public string Title { get; init; } = "";
+
+    [CommandOption("author", 'a', IsRequired = true, Description = "Book author.")]
+    public string Author { get; init; } = "";
+
+    [CommandOption("published", 'p', Description = "Book publish date.")]
+    public DateTimeOffset Published { get; init; } = CreateRandomDate();
+
+    [CommandOption("isbn", 'n', Description = "Book ISBN.")]
+    public Isbn Isbn { get; init; } = CreateRandomIsbn();
+
+    public BookAddCommand(LibraryProvider libraryProvider)
     {
-        private readonly LibraryProvider _libraryProvider;
+        _libraryProvider = libraryProvider;
-
-        [CommandParameter(0, Name = "title", Description = "Book title.")]
-        public string Title { get; init; } = "";
-
-        [CommandOption("author", 'a', IsRequired = true, Description = "Book author.")]
-        public string Author { get; init; } = "";
-
-        [CommandOption("published", 'p', Description = "Book publish date.")]
-        public DateTimeOffset Published { get; init; } = CreateRandomDate();
-
-        [CommandOption("isbn", 'n', Description = "Book ISBN.")]
-        public Isbn Isbn { get; init; } = CreateRandomIsbn();
-
-        public BookAddCommand(LibraryProvider libraryProvider)
-        {
-            _libraryProvider = libraryProvider;
-        }
-
-        public ValueTask ExecuteAsync(IConsole console)
-        {
-            if (_libraryProvider.TryGetBook(Title) is not null)
-                throw new CommandException("Book already exists.", 10);
-
-            var book = new Book(Title, Author, Published, Isbn);
-            _libraryProvider.AddBook(book);
-
-            console.Output.WriteLine("Book added.");
-            console.Output.WriteBook(book);
-
-            return default;
-        }
     }
 
-    public partial class BookAddCommand
+    public ValueTask ExecuteAsync(IConsole console)
     {
-        private static readonly Random Random = new();
+        if (_libraryProvider.TryGetBook(Title) is not null)
+            throw new CommandException("Book already exists.", 10);
 
-        private static DateTimeOffset CreateRandomDate() => new(
+        var book = new Book(Title, Author, Published, Isbn);
-            Random.Next(1800, 2020),
+        _libraryProvider.AddBook(book);
-            Random.Next(1, 12),
-            Random.Next(1, 28),
-            Random.Next(1, 23),
-            Random.Next(1, 59),
-            Random.Next(1, 59),
-            TimeSpan.Zero
-        );
 
-        private static Isbn CreateRandomIsbn() => new(
+        console.Output.WriteLine("Book added.");
-            Random.Next(0, 999),
+        console.Output.WriteBook(book);
-            Random.Next(0, 99),
+
-            Random.Next(0, 99999),
+        return default;
-            Random.Next(0, 99),
-            Random.Next(0, 9)
-        );
     }
+}
+
+public partial class BookAddCommand
+{
+    private static readonly Random Random = new();
+
+    private static DateTimeOffset CreateRandomDate() => new(
+        Random.Next(1800, 2020),
+        Random.Next(1, 12),
+        Random.Next(1, 28),
+        Random.Next(1, 23),
+        Random.Next(1, 59),
+        Random.Next(1, 59),
+        TimeSpan.Zero
+    );
+
+    private static Isbn CreateRandomIsbn() => new(
+        Random.Next(0, 999),
+        Random.Next(0, 99),
+        Random.Next(0, 99999),
+        Random.Next(0, 99),
+        Random.Next(0, 9)
+    );
 }

CliFx.Demo/Commands/BookCommand.cs

@@ -5,31 +5,30 @@ using CliFx.Demo.Utils;
 using CliFx.Exceptions;
 using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book", Description = "Retrieve a book from the library.")]
+public class BookCommand : ICommand
 {
-    [Command("book", Description = "Retrieve a book from the library.")]
+    private readonly LibraryProvider _libraryProvider;
-    public class BookCommand : ICommand
+
+    [CommandParameter(0, Name = "title", Description = "Title of the book to retrieve.")]
+    public string Title { get; init; } = "";
+
+    public BookCommand(LibraryProvider libraryProvider)
     {
-        private readonly LibraryProvider _libraryProvider;
+        _libraryProvider = libraryProvider;
+    }
 
-        [CommandParameter(0, Name = "title", Description = "Title of the book to retrieve.")]
+    public ValueTask ExecuteAsync(IConsole console)
-        public string Title { get; init; } = "";
+    {
+        var book = _libraryProvider.TryGetBook(Title);
 
-        public BookCommand(LibraryProvider libraryProvider)
+        if (book is null)
-        {
+            throw new CommandException("Book not found.", 10);
-            _libraryProvider = libraryProvider;
-        }
 
-        public ValueTask ExecuteAsync(IConsole console)
+        console.Output.WriteBook(book);
-        {
-            var book = _libraryProvider.TryGetBook(Title);
 
-            if (book is null)
+        return default;
-                throw new CommandException("Book not found.", 10);
-
-            console.Output.WriteBook(book);
-
-            return default;
-        }
     }
 }

CliFx.Demo/Commands/BookListCommand.cs

@@ -4,34 +4,33 @@ using CliFx.Demo.Domain;
 using CliFx.Demo.Utils;
 using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book list", Description = "List all books in the library.")]
+public class BookListCommand : ICommand
 {
-    [Command("book list", Description = "List all books in the library.")]
+    private readonly LibraryProvider _libraryProvider;
-    public class BookListCommand : ICommand
+
+    public BookListCommand(LibraryProvider libraryProvider)
     {
-        private readonly LibraryProvider _libraryProvider;
+        _libraryProvider = libraryProvider;
+    }
 
-        public BookListCommand(LibraryProvider libraryProvider)
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        var library = _libraryProvider.GetLibrary();
+
+        for (var i = 0; i < library.Books.Count; i++)
         {
-            _libraryProvider = libraryProvider;
+            // Add margin
+            if (i != 0)
+                console.Output.WriteLine();
+
+            // Render book
+            var book = library.Books[i];
+            console.Output.WriteBook(book);
         }
 
-        public ValueTask ExecuteAsync(IConsole console)
+        return default;
-        {
-            var library = _libraryProvider.GetLibrary();
-
-            for (var i = 0; i < library.Books.Count; i++)
-            {
-                // Add margin
-                if (i != 0)
-                    console.Output.WriteLine();
-
-                // Render book
-                var book = library.Books[i];
-                console.Output.WriteBook(book);
-            }
-
-            return default;
-        }
     }
 }

CliFx.Demo/Commands/BookRemoveCommand.cs

@@ -4,33 +4,32 @@ using CliFx.Demo.Domain;
 using CliFx.Exceptions;
 using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book remove", Description = "Remove a book from the library.")]
+public class BookRemoveCommand : ICommand
 {
-    [Command("book remove", Description = "Remove a book from the library.")]
+    private readonly LibraryProvider _libraryProvider;
-    public class BookRemoveCommand : ICommand
+
+    [CommandParameter(0, Name = "title", Description = "Title of the book to remove.")]
+    public string Title { get; init; } = "";
+
+    public BookRemoveCommand(LibraryProvider libraryProvider)
     {
-        private readonly LibraryProvider _libraryProvider;
+        _libraryProvider = libraryProvider;
+    }
 
-        [CommandParameter(0, Name = "title", Description = "Title of the book to remove.")]
+    public ValueTask ExecuteAsync(IConsole console)
-        public string Title { get; init; } = "";
+    {
+        var book = _libraryProvider.TryGetBook(Title);
 
-        public BookRemoveCommand(LibraryProvider libraryProvider)
+        if (book is null)
-        {
+            throw new CommandException("Book not found.", 10);
-            _libraryProvider = libraryProvider;
-        }
 
-        public ValueTask ExecuteAsync(IConsole console)
+        _libraryProvider.RemoveBook(book);
-        {
-            var book = _libraryProvider.TryGetBook(Title);
 
-            if (book is null)
+        console.Output.WriteLine($"Book {Title} removed.");
-                throw new CommandException("Book not found.", 10);
 
-            _libraryProvider.RemoveBook(book);
+        return default;
-
-            console.Output.WriteLine($"Book {Title} removed.");
-
-            return default;
-        }
     }
 }

CliFx.Demo/Domain/Book.cs

@@ -1,23 +1,22 @@
 using System;
 
-namespace CliFx.Demo.Domain
+namespace CliFx.Demo.Domain;
+
+public class Book
 {
-    public class Book
+    public string Title { get; }
+
+    public string Author { get; }
+
+    public DateTimeOffset Published { get; }
+
+    public Isbn Isbn { get; }
+
+    public Book(string title, string author, DateTimeOffset published, Isbn isbn)
     {
-        public string Title { get; }
+        Title = title;
-
+        Author = author;
-        public string Author { get; }
+        Published = published;
-
+        Isbn = isbn;
-        public DateTimeOffset Published { get; }
-
-        public Isbn Isbn { get; }
-
-        public Book(string title, string author, DateTimeOffset published, Isbn isbn)
-        {
-            Title = title;
-            Author = author;
-            Published = published;
-            Isbn = isbn;
-        }
     }
 }

CliFx.Demo/Domain/Isbn.cs

@@ -1,45 +1,44 @@
 using System;
 
-namespace CliFx.Demo.Domain
+namespace CliFx.Demo.Domain;
+
+public partial class Isbn
 {
-    public partial class Isbn
+    public int EanPrefix { get; }
+
+    public int RegistrationGroup { get; }
+
+    public int Registrant { get; }
+
+    public int Publication { get; }
+
+    public int CheckDigit { get; }
+
+    public Isbn(int eanPrefix, int registrationGroup, int registrant, int publication, int checkDigit)
     {
-        public int EanPrefix { get; }
+        EanPrefix = eanPrefix;
-
+        RegistrationGroup = registrationGroup;
-        public int RegistrationGroup { get; }
+        Registrant = registrant;
-
+        Publication = publication;
-        public int Registrant { get; }
+        CheckDigit = checkDigit;
-
-        public int Publication { get; }
-
-        public int CheckDigit { get; }
-
-        public Isbn(int eanPrefix, int registrationGroup, int registrant, int publication, int checkDigit)
-        {
-            EanPrefix = eanPrefix;
-            RegistrationGroup = registrationGroup;
-            Registrant = registrant;
-            Publication = publication;
-            CheckDigit = checkDigit;
-        }
-
-        public override string ToString() =>
-            $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
     }
 
-    public partial class Isbn
+    public override string ToString() =>
-    {
+        $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
-        public static Isbn Parse(string value, IFormatProvider formatProvider)
+}
-        {
-            var components = value.Split('-', 5, StringSplitOptions.RemoveEmptyEntries);
 
-            return new Isbn(
+public partial class Isbn
-                int.Parse(components[0], formatProvider),
+{
-                int.Parse(components[1], formatProvider),
+    public static Isbn Parse(string value, IFormatProvider formatProvider)
-                int.Parse(components[2], formatProvider),
+    {
-                int.Parse(components[3], formatProvider),
+        var components = value.Split('-', 5, StringSplitOptions.RemoveEmptyEntries);
-                int.Parse(components[4], formatProvider)
+
-            );
+        return new Isbn(
-        }
+            int.Parse(components[0], formatProvider),
+            int.Parse(components[1], formatProvider),
+            int.Parse(components[2], formatProvider),
+            int.Parse(components[3], formatProvider),
+            int.Parse(components[4], formatProvider)
+        );
     }
 }

CliFx.Demo/Domain/Library.cs

@@ -2,35 +2,34 @@
 using System.Collections.Generic;
 using System.Linq;
 
-namespace CliFx.Demo.Domain
+namespace CliFx.Demo.Domain;
+
+public partial class Library
 {
-    public partial class Library
+    public IReadOnlyList<Book> Books { get; }
+
+    public Library(IReadOnlyList<Book> books)
     {
-        public IReadOnlyList<Book> Books { get; }
+        Books = books;
-
-        public Library(IReadOnlyList<Book> books)
-        {
-            Books = books;
-        }
-
-        public Library WithBook(Book book)
-        {
-            var books = Books.ToList();
-            books.Add(book);
-
-            return new Library(books);
-        }
-
-        public Library WithoutBook(Book book)
-        {
-            var books = Books.Where(b => b != book).ToArray();
-
-            return new Library(books);
-        }
     }
 
-    public partial class Library
+    public Library WithBook(Book book)
     {
-        public static Library Empty { get; } = new(Array.Empty<Book>());
+        var books = Books.ToList();
+        books.Add(book);
+
+        return new Library(books);
     }
+
+    public Library WithoutBook(Book book)
+    {
+        var books = Books.Where(b => b != book).ToArray();
+
+        return new Library(books);
+    }
+}
+
+public partial class Library
+{
+    public static Library Empty { get; } = new(Array.Empty<Book>());
 }

CliFx.Demo/Domain/LibraryProvider.cs

@@ -2,40 +2,39 @@
 using System.Linq;
 using Newtonsoft.Json;
 
-namespace CliFx.Demo.Domain
+namespace CliFx.Demo.Domain;
+
+public class LibraryProvider
 {
-    public class LibraryProvider
+    private static string StorageFilePath { get; } = Path.Combine(Directory.GetCurrentDirectory(), "Library.json");
+
+    private void StoreLibrary(Library library)
     {
-        private static string StorageFilePath { get; } = Path.Combine(Directory.GetCurrentDirectory(), "Library.json");
+        var data = JsonConvert.SerializeObject(library);
+        File.WriteAllText(StorageFilePath, data);
+    }
 
-        private void StoreLibrary(Library library)
+    public Library GetLibrary()
-        {
+    {
-            var data = JsonConvert.SerializeObject(library);
+        if (!File.Exists(StorageFilePath))
-            File.WriteAllText(StorageFilePath, data);
+            return Library.Empty;
-        }
 
-        public Library GetLibrary()
+        var data = File.ReadAllText(StorageFilePath);
-        {
-            if (!File.Exists(StorageFilePath))
-                return Library.Empty;
 
-            var data = File.ReadAllText(StorageFilePath);
+        return JsonConvert.DeserializeObject<Library>(data) ?? Library.Empty;
+    }
 
-            return JsonConvert.DeserializeObject<Library>(data) ?? Library.Empty;
+    public Book? TryGetBook(string title) => GetLibrary().Books.FirstOrDefault(b => b.Title == title);
-        }
 
-        public Book? TryGetBook(string title) => GetLibrary().Books.FirstOrDefault(b => b.Title == title);
+    public void AddBook(Book book)
+    {
+        var updatedLibrary = GetLibrary().WithBook(book);
+        StoreLibrary(updatedLibrary);
+    }
 
-        public void AddBook(Book book)
+    public void RemoveBook(Book book)
-        {
+    {
-            var updatedLibrary = GetLibrary().WithBook(book);
+        var updatedLibrary = GetLibrary().WithoutBook(book);
-            StoreLibrary(updatedLibrary);
+        StoreLibrary(updatedLibrary);
-        }
-
-        public void RemoveBook(Book book)
-        {
-            var updatedLibrary = GetLibrary().WithoutBook(book);
-            StoreLibrary(updatedLibrary);
-        }
     }
 }

CliFx.Demo/Program.cs

@@ -1,36 +1,25 @@
-using System;
+using CliFx;
-using System.Threading.Tasks;
 using CliFx.Demo.Commands;
 using CliFx.Demo.Domain;
 using Microsoft.Extensions.DependencyInjection;
 
-namespace CliFx.Demo
+// We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
-{
+var services = new ServiceCollection();
-    public static class Program
-    {
-        private static IServiceProvider GetServiceProvider()
-        {
-            // We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
-            var services = new ServiceCollection();
 
-            // Register services
+// Register services
-            services.AddSingleton<LibraryProvider>();
+services.AddSingleton<LibraryProvider>();
 
-            // Register commands
+// Register commands
-            services.AddTransient<BookCommand>();
+services.AddTransient<BookCommand>();
-            services.AddTransient<BookAddCommand>();
+services.AddTransient<BookAddCommand>();
-            services.AddTransient<BookRemoveCommand>();
+services.AddTransient<BookRemoveCommand>();
-            services.AddTransient<BookListCommand>();
+services.AddTransient<BookListCommand>();
 
-            return services.BuildServiceProvider();
+var serviceProvider = services.BuildServiceProvider();
-        }
 
-        public static async Task<int> Main() =>
+return await new CliApplicationBuilder()
-            await new CliApplicationBuilder()
+    .SetDescription("Demo application showcasing CliFx features.")
-                .SetDescription("Demo application showcasing CliFx features.")
+    .AddCommandsFromThisAssembly()
-                .AddCommandsFromThisAssembly()
+    .UseTypeActivator(serviceProvider.GetRequiredService)
-                .UseTypeActivator(GetServiceProvider().GetRequiredService)
+    .Build()
-                .Build()
+    .RunAsync();
-                .RunAsync();
-    }
-}

CliFx.Demo/Utils/ConsoleExtensions.cs

@@ -2,36 +2,35 @@
 using CliFx.Demo.Domain;
 using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Utils
+namespace CliFx.Demo.Utils;
+
+internal static class ConsoleExtensions
 {
-    internal static class ConsoleExtensions
+    public static void WriteBook(this ConsoleWriter writer, Book book)
     {
-        public static void WriteBook(this ConsoleWriter writer, Book book)
+        // Title
-        {
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
-            // Title
+            writer.WriteLine(book.Title);
-            using (writer.Console.WithForegroundColor(ConsoleColor.White))
-                writer.WriteLine(book.Title);
 
-            // Author
+        // Author
-            writer.Write("  ");
+        writer.Write("  ");
-            writer.Write("Author: ");
+        writer.Write("Author: ");
 
-            using (writer.Console.WithForegroundColor(ConsoleColor.White))
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
-                writer.WriteLine(book.Author);
+            writer.WriteLine(book.Author);
 
-            // Published
+        // Published
-            writer.Write("  ");
+        writer.Write("  ");
-            writer.Write("Published: ");
+        writer.Write("Published: ");
 
-            using (writer.Console.WithForegroundColor(ConsoleColor.White))
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
-                writer.WriteLine($"{book.Published:d}");
+            writer.WriteLine($"{book.Published:d}");
 
-            // ISBN
+        // ISBN
-            writer.Write("  ");
+        writer.Write("  ");
-            writer.Write("ISBN: ");
+        writer.Write("ISBN: ");
 
-            using (writer.Console.WithForegroundColor(ConsoleColor.White))
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
-                writer.WriteLine(book.Isbn);
+            writer.WriteLine(book.Isbn);
-        }
     }
 }

CliFx.Tests.Dummy/CliFx.Tests.Dummy.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>

CliFx.Tests.Dummy/Commands/ConsoleTestCommand.cs

@@ -3,22 +3,21 @@ using System.Threading.Tasks;
 using CliFx.Attributes;
 using CliFx.Infrastructure;
 
-namespace CliFx.Tests.Dummy.Commands
+namespace CliFx.Tests.Dummy.Commands;
+
+[Command("console-test")]
+public class ConsoleTestCommand : ICommand
 {
-    [Command("console-test")]
+    public ValueTask ExecuteAsync(IConsole console)
-    public class ConsoleTestCommand : ICommand
     {
-        public ValueTask ExecuteAsync(IConsole console)
+        var input = console.Input.ReadToEnd();
+
+        using (console.WithColors(ConsoleColor.Black, ConsoleColor.White))
         {
-            var input = console.Input.ReadToEnd();
+            console.Output.WriteLine(input);
-
+            console.Error.WriteLine(input);
-            using (console.WithColors(ConsoleColor.Black, ConsoleColor.White))
-            {
-                console.Output.WriteLine(input);
-                console.Error.WriteLine(input);
-            }
-
-            return default;
         }
+
+        return default;
     }
 }

CliFx.Tests.Dummy/Commands/EnvironmentTestCommand.cs

@@ -2,19 +2,18 @@
 using CliFx.Attributes;
 using CliFx.Infrastructure;
 
-namespace CliFx.Tests.Dummy.Commands
+namespace CliFx.Tests.Dummy.Commands;
+
+[Command("env-test")]
+public class EnvironmentTestCommand : ICommand
 {
-    [Command("env-test")]
+    [CommandOption("target", EnvironmentVariable = "ENV_TARGET")]
-    public class EnvironmentTestCommand : ICommand
+    public string GreetingTarget { get; set; } = "World";
+
+    public ValueTask ExecuteAsync(IConsole console)
     {
-        [CommandOption("target", EnvironmentVariable = "ENV_TARGET")]
+        console.Output.WriteLine($"Hello {GreetingTarget}!");
-        public string GreetingTarget { get; set; } = "World";
 
-        public ValueTask ExecuteAsync(IConsole console)
+        return default;
-        {
-            console.Output.WriteLine($"Hello {GreetingTarget}!");
-
-            return default;
-        }
     }
 }

CliFx.Tests.Dummy/Program.cs

@@ -1,24 +1,22 @@
 using System.Reflection;
 using System.Threading.Tasks;
 
-namespace CliFx.Tests.Dummy
+namespace CliFx.Tests.Dummy;
+// This dummy application is used in tests for scenarios
+// that require an external process to properly verify.
+
+public static partial class Program
 {
-    // This dummy application is used in tests for scenarios
+    public static Assembly Assembly { get; } = typeof(Program).Assembly;
-    // that require an external process to properly verify.
 
-    public static partial class Program
+    public static string Location { get; } = Assembly.Location;
-    {
+}
-        public static Assembly Assembly { get; } = typeof(Program).Assembly;
 
-        public static string Location { get; } = Assembly.Location;
+public static partial class Program
-    }
+{
-
+    public static async Task Main() =>
-    public static partial class Program
+        await new CliApplicationBuilder()
-    {
+            .AddCommandsFromThisAssembly()
-        public static async Task Main() =>
+            .Build()
-            await new CliApplicationBuilder()
+            .RunAsync();
-                .AddCommandsFromThisAssembly()
-                .Build()
-                .RunAsync();
-    }
 }

CliFx.Tests/ApplicationSpecs.cs

@@ -6,81 +6,80 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class ApplicationSpecs : SpecsBase
 {
-    public class ApplicationSpecs : SpecsBase
+    public ApplicationSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
     {
-        public ApplicationSpecs(ITestOutputHelper testOutput)
+    }
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+    [Fact]
-        public async Task Application_can_be_created_with_minimal_configuration()
+    public async Task Application_can_be_created_with_minimal_configuration()
-        {
+    {
-            // Act
+        // Act
-            var app = new CliApplicationBuilder()
+        var app = new CliApplicationBuilder()
-                .AddCommandsFromThisAssembly()
+            .AddCommandsFromThisAssembly()
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            var exitCode = await app.RunAsync(
+        var exitCode = await app.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Application_can_be_created_with_a_fully_customized_configuration()
+    public async Task Application_can_be_created_with_a_fully_customized_configuration()
-        {
+    {
-            // Act
+        // Act
-            var app = new CliApplicationBuilder()
+        var app = new CliApplicationBuilder()
-                .AddCommand<NoOpCommand>()
+            .AddCommand<NoOpCommand>()
-                .AddCommandsFrom(typeof(NoOpCommand).Assembly)
+            .AddCommandsFrom(typeof(NoOpCommand).Assembly)
-                .AddCommands(new[] {typeof(NoOpCommand)})
+            .AddCommands(new[] {typeof(NoOpCommand)})
-                .AddCommandsFrom(new[] {typeof(NoOpCommand).Assembly})
+            .AddCommandsFrom(new[] {typeof(NoOpCommand).Assembly})
-                .AddCommandsFromThisAssembly()
+            .AddCommandsFromThisAssembly()
-                .AllowDebugMode()
+            .AllowDebugMode()
-                .AllowPreviewMode()
+            .AllowPreviewMode()
-                .SetTitle("test")
+            .SetTitle("test")
-                .SetExecutableName("test")
+            .SetExecutableName("test")
-                .SetVersion("test")
+            .SetVersion("test")
-                .SetDescription("test")
+            .SetDescription("test")
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .UseTypeActivator(Activator.CreateInstance!)
+            .UseTypeActivator(Activator.CreateInstance!)
-                .Build();
+            .Build();
 
-            var exitCode = await app.RunAsync(
+        var exitCode = await app.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Application_configuration_fails_if_an_invalid_command_is_registered()
+    public async Task Application_configuration_fails_if_an_invalid_command_is_registered()
-        {
+    {
-            // Act
+        // Act
-            var app = new CliApplicationBuilder()
+        var app = new CliApplicationBuilder()
-                .AddCommand(typeof(ApplicationSpecs))
+            .AddCommand(typeof(ApplicationSpecs))
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            var exitCode = await app.RunAsync(
+        var exitCode = await app.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("not a valid command");
+        stdErr.Should().Contain("not a valid command");
-        }
     }
 }

CliFx.Tests/CancellationSpecs.cs

@@ -6,22 +6,22 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
-{
-    public class CancellationSpecs : SpecsBase
-    {
-        public CancellationSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+public class CancellationSpecs : SpecsBase
-        public async Task Command_can_register_to_receive_a_cancellation_signal_from_the_console()
+{
-        {
+    public CancellationSpecs(ITestOutputHelper testOutput)
-            // Arrange
+        : base(testOutput)
-            var commandType = DynamicCommandBuilder.Compile(
+    {
-                // language=cs
+    }
-                @"
+
+    [Fact]
+    public async Task Command_can_register_to_receive_a_cancellation_signal_from_the_console()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -44,24 +44,23 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            FakeConsole.RequestCancellation(TimeSpan.FromSeconds(0.2));
+        FakeConsole.RequestCancellation(TimeSpan.FromSeconds(0.2));
 
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdOut.Trim().Should().Be("Cancelled");
+        stdOut.Trim().Should().Be("Cancelled");
-        }
     }
 }

CliFx.Tests/CliFx.Tests.csproj

@@ -1,9 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
-    <IsPackable>false</IsPackable>
-    <IsTestProject>true</IsTestProject>
     <CollectCoverage>true</CollectCoverage>
     <CoverletOutputFormat>opencover</CoverletOutputFormat>
   </PropertyGroup>
@@ -13,14 +11,15 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="CliWrap" Version="3.3.2" />
+    <PackageReference Include="Basic.Reference.Assemblies" Version="1.2.4" />
-    <PackageReference Include="FluentAssertions" Version="5.10.3" />
+    <PackageReference Include="CliWrap" Version="3.4.0" />
+    <PackageReference Include="FluentAssertions" Version="6.3.0" />
     <PackageReference Include="GitHubActionsTestLogger" Version="1.2.0" />
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.4.0" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" PrivateAssets="all" />
-    <PackageReference Include="coverlet.msbuild" Version="3.0.3" PrivateAssets="all" />
+    <PackageReference Include="coverlet.msbuild" Version="3.1.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Tests/ConsoleSpecs.cs

@@ -1,6 +1,9 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
+using System.Text;
 using System.Threading.Tasks;
+using CliFx.Infrastructure;
 using CliFx.Tests.Utils;
 using CliWrap;
 using CliWrap.Buffered;
@@ -8,42 +11,42 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class ConsoleSpecs : SpecsBase
 {
-    public class ConsoleSpecs : SpecsBase
+    public ConsoleSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
     {
-        public ConsoleSpecs(ITestOutputHelper testOutput)
+    }
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+    [Fact]
-        public async Task Real_console_maps_directly_to_system_console()
+    public async Task Real_console_maps_directly_to_system_console()
-        {
+    {
-            // Can't verify our own console output, so using an
+        // Can't verify our own console output, so using an
-            // external process for this test.
+        // external process for this test.
 
-            // Arrange
+        // Arrange
-            var command = "Hello world" | Cli.Wrap("dotnet")
+        var command = "Hello world" | Cli.Wrap("dotnet")
-                .WithArguments(a => a
+            .WithArguments(a => a
-                    .Add(Dummy.Program.Location)
+                .Add(Dummy.Program.Location)
-                    .Add("console-test"));
+                .Add("console-test"));
 
-            // Act
+        // Act
-            var result = await command.ExecuteBufferedAsync();
+        var result = await command.ExecuteBufferedAsync();
 
-            // Assert
+        // Assert
-            result.StandardOutput.Trim().Should().Be("Hello world");
+        result.StandardOutput.Trim().Should().Be("Hello world");
-            result.StandardError.Trim().Should().Be("Hello world");
+        result.StandardError.Trim().Should().Be("Hello world");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Fake_console_does_not_leak_to_system_console()
+    public async Task Fake_console_does_not_leak_to_system_console()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {   
@@ -63,43 +66,43 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
 
-            Console.OpenStandardInput().Should().NotBe(FakeConsole.Input.BaseStream);
+        Console.OpenStandardInput().Should().NotBeSameAs(FakeConsole.Input.BaseStream);
-            Console.OpenStandardOutput().Should().NotBe(FakeConsole.Output.BaseStream);
+        Console.OpenStandardOutput().Should().NotBeSameAs(FakeConsole.Output.BaseStream);
-            Console.OpenStandardError().Should().NotBe(FakeConsole.Error.BaseStream);
+        Console.OpenStandardError().Should().NotBeSameAs(FakeConsole.Error.BaseStream);
 
-            Console.ForegroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
+        Console.ForegroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
-            Console.BackgroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
+        Console.BackgroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
 
-            // This fails because tests don't spawn a console window
+        // This fails because tests don't spawn a console window
-            //Console.CursorLeft.Should().NotBe(42);
+        //Console.CursorLeft.Should().NotBe(42);
-            //Console.CursorTop.Should().NotBe(24);
+        //Console.CursorTop.Should().NotBe(24);
 
-            FakeConsole.IsInputRedirected.Should().BeTrue();
+        FakeConsole.IsInputRedirected.Should().BeTrue();
-            FakeConsole.IsOutputRedirected.Should().BeTrue();
+        FakeConsole.IsOutputRedirected.Should().BeTrue();
-            FakeConsole.IsErrorRedirected.Should().BeTrue();
+        FakeConsole.IsErrorRedirected.Should().BeTrue();
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Fake_console_can_be_used_with_an_in_memory_backing_store()
+    public async Task Fake_console_can_be_used_with_an_in_memory_backing_store()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {   
@@ -114,26 +117,42 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            FakeConsole.WriteInput("Hello world");
+        FakeConsole.WriteInput("Hello world");
 
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("Hello world");
+        stdOut.Trim().Should().Be("Hello world");
-            stdErr.Trim().Should().Be("Hello world");
+        stdErr.Trim().Should().Be("Hello world");
-        }
+    }
+
+    [Fact]
+    public void Console_does_not_emit_preamble_when_used_with_encoding_that_has_it()
+    {
+        // Arrange
+        using var buffer = new MemoryStream();
+        using var consoleWriter = new ConsoleWriter(FakeConsole, buffer, Encoding.UTF8);
+
+        // Act
+        consoleWriter.Write("Hello world");
+        consoleWriter.Flush();
+
+        var output = consoleWriter.Encoding.GetString(buffer.ToArray());
+
+        // Assert
+        output.Should().Be("Hello world");
     }
 }

CliFx.Tests/DirectivesSpecs.cs

@@ -10,71 +10,71 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class DirectivesSpecs : SpecsBase
 {
-    public class DirectivesSpecs : SpecsBase
+    public DirectivesSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
     {
-        public DirectivesSpecs(ITestOutputHelper testOutput)
+    }
-            : base(testOutput)
+
+    [Fact]
+    public async Task Debug_directive_can_be_specified_to_interrupt_execution_until_a_debugger_is_attached()
+    {
+        // Arrange
+        var stdOutBuffer = new StringBuilder();
+
+        var command = Cli.Wrap("dotnet")
+            .WithArguments(a => a
+                .Add(Dummy.Program.Location)
+                .Add("[debug]")) | stdOutBuffer;
+
+        // Act
+        try
         {
-        }
+            // This has a timeout just in case the execution hangs forever
+            using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
 
-        [Fact]
+            var task = command.ExecuteAsync(cts.Token);
-        public async Task Debug_directive_can_be_specified_to_interrupt_execution_until_a_debugger_is_attached()
-        {
-            // Arrange
-            var stdOutBuffer = new StringBuilder();
 
-            var command = Cli.Wrap("dotnet")
+            // We can't attach a debugger programmatically, so the application
-                .WithArguments(a => a
+            // will hang indefinitely.
-                    .Add(Dummy.Program.Location)
+            // To work around it, we will wait until the application writes
-                    .Add("[debug]")) | stdOutBuffer;
+            // something to the standard output and then kill it.
-
+            while (true)
-            // Act
-            try
             {
-                // This has a timeout just in case the execution hangs forever
+                if (stdOutBuffer.Length > 0)
-                using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
-
-                var task = command.ExecuteAsync(cts.Token);
-
-                // We can't attach a debugger programmatically, so the application
-                // will hang indefinitely.
-                // To work around it, we will wait until the application writes
-                // something to the standard output and then kill it.
-                while (true)
                 {
-                    if (stdOutBuffer.Length > 0)
+                    cts.Cancel();
-                    {
+                    break;
-                        cts.Cancel();
-                        break;
-                    }
-
-                    await Task.Delay(100, cts.Token);
                 }
 
-                await task;
+                await Task.Delay(100, cts.Token);
-            }
-            catch (OperationCanceledException)
-            {
-                // It's expected to fail
             }
 
-            var stdOut = stdOutBuffer.ToString();
+            await task;
-
+        }
-            // Assert
+        catch (OperationCanceledException)
-            stdOut.Should().Contain("Attach debugger to");
+        {
-
+            // It's expected to fail
-            TestOutput.WriteLine(stdOut);
         }
 
-        [Fact]
+        var stdOut = stdOutBuffer.ToString();
-        public async Task Preview_directive_can_be_specified_to_print_command_input()
+
-        {
+        // Assert
-            // Arrange
+        stdOut.Should().Contain("Attach debugger to");
-            var commandType = DynamicCommandBuilder.Compile(
+
-                // language=cs
+        TestOutput.WriteLine(stdOut);
-                @"
+    }
+
+    [Fact]
+    public async Task Preview_directive_can_be_specified_to_print_command_input()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command(""cmd"")]
 public class Command : ICommand
 {
@@ -82,31 +82,30 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .AllowPreviewMode()
+            .AllowPreviewMode()
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"[preview]", "cmd", "param", "-abc", "--option", "foo"},
+            new[] {"[preview]", "cmd", "param", "-abc", "--option", "foo"},
-                new Dictionary<string, string>
+            new Dictionary<string, string>
-                {
+            {
-                    ["ENV_QOP"] = "hello",
+                ["ENV_QOP"] = "hello",
-                    ["ENV_KIL"] = "world"
+                ["ENV_KIL"] = "world"
-                }
+            }
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Should().ContainAllInOrder(
+        stdOut.Should().ContainAllInOrder(
-                "cmd", "<param>", "[-a]", "[-b]", "[-c]", "[--option \"foo\"]",
+            "cmd", "<param>", "[-a]", "[-b]", "[-c]", "[--option \"foo\"]",
-                "ENV_QOP", "=", "\"hello\"",
+            "ENV_QOP", "=", "\"hello\"",
-                "ENV_KIL", "=", "\"world\""
+            "ENV_KIL", "=", "\"world\""
-            );
+        );
-        }
     }
 }

CliFx.Tests/EnvironmentSpecs.cs

@@ -10,28 +10,28 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
-{
-    public class EnvironmentSpecs : SpecsBase
-    {
-        public EnvironmentSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+public class EnvironmentSpecs : SpecsBase
-        public async Task Option_can_fall_back_to_an_environment_variable()
+{
-        {
+    public EnvironmentSpecs(ITestOutputHelper testOutput)
-            // Arrange
+        : base(testOutput)
-            var commandType = DynamicCommandBuilder.Compile(
+    {
-                // language=cs
+    }
-                @"
+
+    [Fact]
+    public async Task Option_can_fall_back_to_an_environment_variable()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandOption(""foo"", IsRequired = true, EnvironmentVariable = ""ENV_FOO"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console)
     {
         console.Output.WriteLine(Foo);
@@ -40,40 +40,40 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>
+            new Dictionary<string, string>
-                {
+            {
-                    ["ENV_FOO"] = "bar"
+                ["ENV_FOO"] = "bar"
-                }
+            }
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("bar");
+        stdOut.Trim().Should().Be("bar");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Option_does_not_fall_back_to_an_environment_variable_if_a_value_is_provided_through_arguments()
+    public async Task Option_does_not_fall_back_to_an_environment_variable_if_a_value_is_provided_through_arguments()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console)
     {
         console.Output.WriteLine(Foo);
@@ -82,87 +82,87 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"--foo", "baz"},
+            new[] {"--foo", "baz"},
-                new Dictionary<string, string>
+            new Dictionary<string, string>
-                {
+            {
-                    ["ENV_FOO"] = "bar"
+                ["ENV_FOO"] = "bar"
-                }
+            }
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("baz");
+        stdOut.Trim().Should().Be("baz");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Option_of_non_scalar_type_can_receive_multiple_values_from_an_environment_variable()
+    public async Task Option_of_non_scalar_type_can_receive_multiple_values_from_an_environment_variable()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
     public IReadOnlyList<string> Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console)
     {
         foreach (var i in Foo)
             console.Output.WriteLine(i);
-        
+
         return default;
     }
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>
+            new Dictionary<string, string>
-                {
+            {
-                    ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
+                ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
-                }
+            }
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Should().ConsistOfLines(
+        stdOut.Should().ConsistOfLines(
-                "bar",
+            "bar",
-                "baz"
+            "baz"
-            );
+        );
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Option_of_scalar_type_always_receives_a_single_value_from_an_environment_variable()
+    public async Task Option_of_scalar_type_always_receives_a_single_value_from_an_environment_variable()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console)
     {
         console.Output.WriteLine(Foo);
@@ -171,40 +171,40 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>
+            new Dictionary<string, string>
-                {
+            {
-                    ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
+                ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
-                }
+            }
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be($"bar{Path.PathSeparator}baz");
+        stdOut.Trim().Should().Be($"bar{Path.PathSeparator}baz");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Environment_variables_are_matched_case_sensitively()
+    public async Task Environment_variables_are_matched_case_sensitively()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
     public string Foo { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console)
     {
         console.Output.WriteLine(Foo);
@@ -213,48 +213,47 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>
+            new Dictionary<string, string>
-                {
+            {
-                    ["ENV_foo"] = "baz",
+                ["ENV_foo"] = "baz",
-                    ["ENV_FOO"] = "bar",
+                ["ENV_FOO"] = "bar",
-                    ["env_FOO"] = "qop"
+                ["env_FOO"] = "qop"
-                }
+            }
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("bar");
+        stdOut.Trim().Should().Be("bar");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Environment_variables_are_extracted_automatically()
+    public async Task Environment_variables_are_extracted_automatically()
-        {
+    {
-            // Ensures that the environment variables are properly obtained from
+        // Ensures that the environment variables are properly obtained from
-            // System.Environment when they are not provided explicitly to CliApplication.
+        // System.Environment when they are not provided explicitly to CliApplication.
 
-            // Arrange
+        // Arrange
-            var command = Cli.Wrap("dotnet")
+        var command = Cli.Wrap("dotnet")
-                .WithArguments(a => a
+            .WithArguments(a => a
-                    .Add(Dummy.Program.Location)
+                .Add(Dummy.Program.Location)
-                    .Add("env-test"))
+                .Add("env-test"))
-                .WithEnvironmentVariables(e => e
+            .WithEnvironmentVariables(e => e
-                    .Set("ENV_TARGET", "Mars"));
+                .Set("ENV_TARGET", "Mars"));
 
-            // Act
+        // Act
-            var result = await command.ExecuteBufferedAsync();
+        var result = await command.ExecuteBufferedAsync();
 
-            // Assert
+        // Assert
-            result.StandardOutput.Trim().Should().Be("Hello Mars!");
+        result.StandardOutput.Trim().Should().Be("Hello Mars!");
-        }
     }
 }

CliFx.Tests/ErrorReportingSpecs.cs

@@ -7,22 +7,22 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
-{
-    public class ErrorReportingSpecs : SpecsBase
-    {
-        public ErrorReportingSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+public class ErrorReportingSpecs : SpecsBase
-        public async Task Command_can_throw_an_exception_which_exits_with_a_stacktrace()
+{
-        {
+    public ErrorReportingSpecs(ITestOutputHelper testOutput)
-            // Arrange
+        : base(testOutput)
-            var commandType = DynamicCommandBuilder.Compile(
+    {
-                // language=cs
+    }
-                @"
+
+    [Fact]
+    public async Task Command_can_throw_an_exception_which_exits_with_a_stacktrace()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -31,36 +31,36 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdOut.Should().BeEmpty();
+        stdOut.Should().BeEmpty();
-            stdErr.Should().ContainAllInOrder(
+        stdErr.Should().ContainAllInOrder(
-                "System.Exception", "Something went wrong",
+            "System.Exception", "Something went wrong",
-                "at", "CliFx."
+            "at", "CliFx."
-            );
+        );
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Command_can_throw_an_exception_with_an_inner_exception_which_exits_with_a_stacktrace()
+    public async Task Command_can_throw_an_exception_with_an_inner_exception_which_exits_with_a_stacktrace()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -69,37 +69,37 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdOut.Should().BeEmpty();
+        stdOut.Should().BeEmpty();
-            stdErr.Should().ContainAllInOrder(
+        stdErr.Should().ContainAllInOrder(
-                "System.Exception", "Something went wrong",
+            "System.Exception", "Something went wrong",
-                "System.Exception", "Another exception",
+            "System.Exception", "Another exception",
-                "at", "CliFx."
+            "at", "CliFx."
-            );
+        );
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Command_can_throw_a_special_exception_which_exits_with_specified_code_and_message()
+    public async Task Command_can_throw_a_special_exception_which_exits_with_specified_code_and_message()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -108,33 +108,33 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(69);
+        exitCode.Should().Be(69);
-            stdOut.Should().BeEmpty();
+        stdOut.Should().BeEmpty();
-            stdErr.Trim().Should().Be("Something went wrong");
+        stdErr.Trim().Should().Be("Something went wrong");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Command_can_throw_a_special_exception_without_message_which_exits_with_a_stacktrace()
+    public async Task Command_can_throw_a_special_exception_without_message_which_exits_with_a_stacktrace()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -143,36 +143,36 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(69);
+        exitCode.Should().Be(69);
-            stdOut.Should().BeEmpty();
+        stdOut.Should().BeEmpty();
-            stdErr.Should().ContainAllInOrder(
+        stdErr.Should().ContainAllInOrder(
-                "CliFx.Exceptions.CommandException",
+            "CliFx.Exceptions.CommandException",
-                "at", "CliFx."
+            "at", "CliFx."
-            );
+        );
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Command_can_throw_a_special_exception_which_prints_help_text_before_exiting()
+    public async Task Command_can_throw_a_special_exception_which_prints_help_text_before_exiting()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -181,25 +181,24 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .SetDescription("This will be in help text")
+            .SetDescription("This will be in help text")
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(69);
+        exitCode.Should().Be(69);
-            stdOut.Should().Contain("This will be in help text");
+        stdOut.Should().Contain("This will be in help text");
-            stdErr.Trim().Should().Be("Something went wrong");
+        stdErr.Trim().Should().Be("Something went wrong");
-        }
     }
 }

CliFx.Tests/ParameterBindingSpecs.cs

@@ -6,28 +6,28 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
-{
-    public class ParameterBindingSpecs : SpecsBase
-    {
-        public ParameterBindingSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+public class ParameterBindingSpecs : SpecsBase
-        public async Task Parameter_is_bound_from_an_argument_matching_its_order()
+{
-        {
+    public ParameterBindingSpecs(ITestOutputHelper testOutput)
-            // Arrange
+        : base(testOutput)
-            var commandType = DynamicCommandBuilder.Compile(
+    {
-                // language=cs
+    }
-                @"
+
+    [Fact]
+    public async Task Parameter_is_bound_from_an_argument_matching_its_order()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string Bar { get; set; }
 
@@ -35,51 +35,51 @@ public class Command : ICommand
     {
         console.Output.WriteLine(""Foo = "" + Foo);
         console.Output.WriteLine(""Bar = "" + Bar);
-        
+
         return default;
     }
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"one", "two"},
+            new[] {"one", "two"},
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Should().ConsistOfLines(
+        stdOut.Should().ConsistOfLines(
-                "Foo = one",
+            "Foo = one",
-                "Bar = two"
+            "Bar = two"
-            );
+        );
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Parameter_of_non_scalar_type_is_bound_from_remaining_non_option_arguments()
+    public async Task Parameter_of_non_scalar_type_is_bound_from_remaining_non_option_arguments()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string Bar { get; set; }
-    
+
     [CommandParameter(2)]
     public IReadOnlyList<string> Baz { get; set; }
-    
+
     [CommandOption(""boo"")]
     public string Boo { get; set; }
 
@@ -87,147 +87,192 @@ public class Command : ICommand
     {
         console.Output.WriteLine(""Foo = "" + Foo);
         console.Output.WriteLine(""Bar = "" + Bar);
-        
+
         foreach (var i in Baz)
             console.Output.WriteLine(""Baz = "" + i);
-        
+
         return default;
     }
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"one", "two", "three", "four", "five", "--boo", "xxx"},
+            new[] {"one", "two", "three", "four", "five", "--boo", "xxx"},
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Should().ConsistOfLines(
+        stdOut.Should().ConsistOfLines(
-                "Foo = one",
+            "Foo = one",
-                "Bar = two",
+            "Bar = two",
-                "Baz = three",
+            "Baz = three",
-                "Baz = four",
+            "Baz = four",
-                "Baz = five"
+            "Baz = five"
-            );
+        );
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Parameter_binding_fails_if_one_of_the_parameters_has_not_been_provided()
+    public async Task Parameter_is_not_bound_if_there_are_no_arguments_matching_its_order()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
+    [CommandParameter(1, IsRequired = false)]
+    public string Bar { get; set; } = ""xyz"";
+
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        console.Output.WriteLine(""Foo = "" + Foo);
+        console.Output.WriteLine(""Bar = "" + Bar);
+
+        return default;
+    }
+}");
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"abc"},
+            new Dictionary<string, string>()
+        );
+
+        var stdOut = FakeConsole.ReadOutputString();
+
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Should().ConsistOfLines(
+            "Foo = abc",
+            "Bar = xyz"
+        );
+    }
+
+    [Fact]
+    public async Task Parameter_binding_fails_if_a_required_parameter_has_not_been_provided()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
+[Command]
+public class Command : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
     [CommandParameter(1)]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"one"},
+            new[] {"one"},
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Missing parameter(s)");
+        stdErr.Should().Contain("Missing required parameter(s)");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Parameter_binding_fails_if_a_parameter_of_non_scalar_type_has_not_been_provided_with_at_least_one_value()
+    public async Task Parameter_binding_fails_if_a_parameter_of_non_scalar_type_has_not_been_provided_with_at_least_one_value()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public IReadOnlyList<string> Bar { get; set; }
-    
+
     public ValueTask ExecuteAsync(IConsole console) => default;
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"one"},
+            new[] {"one"},
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Missing parameter(s)");
+        stdErr.Should().Contain("Missing required parameter(s)");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Parameter_binding_fails_if_one_of_the_provided_parameters_is_unexpected()
+    public async Task Parameter_binding_fails_if_one_of_the_provided_parameters_is_unexpected()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
     [CommandParameter(0)]
     public string Foo { get; set; }
-    
+
     [CommandParameter(1)]
     public string Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"one", "two", "three"},
+            new[] {"one", "two", "three"},
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Unexpected parameter(s)");
+        stdErr.Should().Contain("Unexpected parameter(s)");
-        }
     }
 }

CliFx.Tests/RoutingSpecs.cs

@@ -6,22 +6,22 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
-{
-    public class RoutingSpecs : SpecsBase
-    {
-        public RoutingSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+public class RoutingSpecs : SpecsBase
-        public async Task Default_command_is_executed_if_provided_arguments_do_not_match_any_named_command()
+{
-        {
+    public RoutingSpecs(ITestOutputHelper testOutput)
-            // Arrange
+        : base(testOutput)
-            var commandTypes = DynamicCommandBuilder.CompileMany(
+    {
-                // language=cs
+    }
-                @"
+
+    [Fact]
+    public async Task Default_command_is_executed_if_provided_arguments_do_not_match_any_named_command()
+    {
+        // Arrange
+        var commandTypes = DynamicCommandBuilder.CompileMany(
+            // language=cs
+            @"
 [Command]
 public class DefaultCommand : ICommand
 {
@@ -53,31 +53,31 @@ public class NamedChildCommand : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommands(commandTypes)
+            .AddCommands(commandTypes)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("default");
+        stdOut.Trim().Should().Be("default");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Specific_named_command_is_executed_if_provided_arguments_match_its_name()
+    public async Task Specific_named_command_is_executed_if_provided_arguments_match_its_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandTypes = DynamicCommandBuilder.CompileMany(
+        var commandTypes = DynamicCommandBuilder.CompileMany(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class DefaultCommand : ICommand
 {
@@ -109,31 +109,31 @@ public class NamedChildCommand : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommands(commandTypes)
+            .AddCommands(commandTypes)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"cmd"},
+            new[] {"cmd"},
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("cmd");
+        stdOut.Trim().Should().Be("cmd");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Specific_named_child_command_is_executed_if_provided_arguments_match_its_name()
+    public async Task Specific_named_child_command_is_executed_if_provided_arguments_match_its_name()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandTypes = DynamicCommandBuilder.CompileMany(
+        var commandTypes = DynamicCommandBuilder.CompileMany(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class DefaultCommand : ICommand
 {
@@ -165,22 +165,21 @@ public class NamedChildCommand : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommands(commandTypes)
+            .AddCommands(commandTypes)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                new[] {"cmd", "child"},
+            new[] {"cmd", "child"},
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("cmd child");
+        stdOut.Trim().Should().Be("cmd child");
-        }
     }
 }

CliFx.Tests/SpecsBase.cs

@@ -3,21 +3,20 @@ using CliFx.Infrastructure;
 using CliFx.Tests.Utils.Extensions;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public abstract class SpecsBase : IDisposable
 {
-    public abstract class SpecsBase : IDisposable
+    public ITestOutputHelper TestOutput { get; }
+
+    public FakeInMemoryConsole FakeConsole { get; } = new();
+
+    protected SpecsBase(ITestOutputHelper testOutput) =>
+        TestOutput = testOutput;
+
+    public void Dispose()
     {
-        public ITestOutputHelper TestOutput { get; }
+        FakeConsole.DumpToTestOutput(TestOutput);
-
+        FakeConsole.Dispose();
-        public FakeInMemoryConsole FakeConsole { get; } = new();
-
-        protected SpecsBase(ITestOutputHelper testOutput) =>
-            TestOutput = testOutput;
-
-        public void Dispose()
-        {
-            FakeConsole.DumpToTestOutput(TestOutput);
-            FakeConsole.Dispose();
-        }
     }
 }

CliFx.Tests/TypeActivationSpecs.cs

@@ -7,22 +7,22 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
-{
-    public class TypeActivationSpecs : SpecsBase
-    {
-        public TypeActivationSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
 
-        [Fact]
+public class TypeActivationSpecs : SpecsBase
-        public async Task Default_type_activator_can_initialize_a_type_if_it_has_a_parameterless_constructor()
+{
-        {
+    public TypeActivationSpecs(ITestOutputHelper testOutput)
-            // Arrange
+        : base(testOutput)
-            var commandType = DynamicCommandBuilder.Compile(
+    {
-                // language=cs
+    }
-                @"
+
+    [Fact]
+    public async Task Default_type_activator_can_initialize_a_type_if_it_has_a_parameterless_constructor()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -33,32 +33,32 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .UseTypeActivator(new DefaultTypeActivator())
+            .UseTypeActivator(new DefaultTypeActivator())
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("foo");
+        stdOut.Trim().Should().Be("foo");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Default_type_activator_fails_if_the_type_does_not_have_a_parameterless_constructor()
+    public async Task Default_type_activator_fails_if_the_type_does_not_have_a_parameterless_constructor()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -67,32 +67,32 @@ public class Command : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .UseTypeActivator(new DefaultTypeActivator())
+            .UseTypeActivator(new DefaultTypeActivator())
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Failed to create an instance of type");
+        stdErr.Should().Contain("Failed to create an instance of type");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Delegate_type_activator_can_initialize_a_type_using_a_custom_function()
+    public async Task Delegate_type_activator_can_initialize_a_type_using_a_custom_function()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -107,32 +107,32 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .UseTypeActivator(type => Activator.CreateInstance(type, "hello world")!)
+            .UseTypeActivator(type => Activator.CreateInstance(type, "hello world")!)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
+        // Assert
-            exitCode.Should().Be(0);
+        exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("hello world");
+        stdOut.Trim().Should().Be("hello world");
-        }
+    }
 
-        [Fact]
+    [Fact]
-        public async Task Delegate_type_activator_fails_if_the_underlying_function_returns_null()
+    public async Task Delegate_type_activator_fails_if_the_underlying_function_returns_null()
-        {
+    {
-            // Arrange
+        // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
+        var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
+            // language=cs
-                @"
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -143,23 +143,22 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
+        var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
+            .AddCommand(commandType)
-                .UseConsole(FakeConsole)
+            .UseConsole(FakeConsole)
-                .UseTypeActivator(_ => null!)
+            .UseTypeActivator(_ => null!)
-                .Build();
+            .Build();
 
-            // Act
+        // Act
-            var exitCode = await application.RunAsync(
+        var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            Array.Empty<string>(),
-                new Dictionary<string, string>()
+            new Dictionary<string, string>()
-            );
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
+        // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Failed to create an instance of type");
+        stdErr.Should().Contain("Failed to create an instance of type");
-        }
     }
 }

CliFx.Tests/Utils/DynamicCommandBuilder.cs

@@ -3,140 +3,133 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using Basic.Reference.Assemblies;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Text;
 
-namespace CliFx.Tests.Utils
+namespace CliFx.Tests.Utils;
+
+// This class uses Roslyn to compile commands dynamically.
+//
+// It allows us to collocate commands with tests more
+// easily, which helps a lot when reasoning about them.
+// Unfortunately, this comes at a cost of static typing,
+// but this is still a worthwhile trade off.
+//
+// Maybe one day C# will allow declaring classes inside
+// methods and doing this will no longer be necessary.
+// Language proposal: https://github.com/dotnet/csharplang/discussions/130
+internal static class DynamicCommandBuilder
 {
-    // This class uses Roslyn to compile commands dynamically.
+    public static IReadOnlyList<Type> CompileMany(string sourceCode)
-    //
-    // It allows us to collocate commands with tests more
-    // easily, which helps a lot when reasoning about them.
-    // Unfortunately, this comes at a cost of static typing,
-    // but this is still a worthwhile trade off.
-    //
-    // Maybe one day C# will allow declaring classes inside
-    // methods and doing this will no longer be necessary.
-    // Language proposal: https://github.com/dotnet/csharplang/discussions/130
-    internal static class DynamicCommandBuilder
     {
-        public static IReadOnlyList<Type> CompileMany(string sourceCode)
+        // Get default system namespaces
+        var defaultSystemNamespaces = new[]
         {
-            // Get default system namespaces
+            "System",
-            var defaultSystemNamespaces = new[]
+            "System.Collections",
-            {
+            "System.Collections.Generic",
-                "System",
+            "System.Linq",
-                "System.Collections",
+            "System.Threading.Tasks",
-                "System.Collections.Generic",
+            "System.Globalization"
-                "System.Linq",
+        };
-                "System.Threading.Tasks",
-                "System.Globalization"
-            };
 
-            // Get default CliFx namespaces
+        // Get default CliFx namespaces
-            var defaultCliFxNamespaces = typeof(ICommand)
+        var defaultCliFxNamespaces = typeof(ICommand)
-                .Assembly
+            .Assembly
-                .GetTypes()
+            .GetTypes()
-                .Where(t => t.IsPublic)
+            .Where(t => t.IsPublic)
-                .Select(t => t.Namespace)
+            .Select(t => t.Namespace)
-                .Distinct()
+            .Distinct()
-                .ToArray();
+            .ToArray();
 
-            // Append default imports to the source code
+        // Append default imports to the source code
-            var sourceCodeWithUsings =
+        var sourceCodeWithUsings =
-                string.Join(Environment.NewLine, defaultSystemNamespaces.Select(n => $"using {n};")) +
+            string.Join(Environment.NewLine, defaultSystemNamespaces.Select(n => $"using {n};")) +
-                string.Join(Environment.NewLine, defaultCliFxNamespaces.Select(n => $"using {n};")) +
+            string.Join(Environment.NewLine, defaultCliFxNamespaces.Select(n => $"using {n};")) +
+            Environment.NewLine +
+            sourceCode;
+
+        // Parse the source code
+        var ast = SyntaxFactory.ParseSyntaxTree(
+            SourceText.From(sourceCodeWithUsings),
+            CSharpParseOptions.Default
+        );
+
+        // Compile the code to IL
+        var compilation = CSharpCompilation.Create(
+            "CliFxTests_DynamicAssembly_" + Guid.NewGuid(),
+            new[] {ast},
+            ReferenceAssemblies.Net50
+                .Append(MetadataReference.CreateFromFile(typeof(ICommand).Assembly.Location))
+                .Append(MetadataReference.CreateFromFile(typeof(DynamicCommandBuilder).Assembly.Location)),
+            // DLL to avoid having to define the Main() method
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
+        );
+
+        var compilationErrors = compilation
+            .GetDiagnostics()
+            .Where(d => d.Severity >= DiagnosticSeverity.Error)
+            .ToArray();
+
+        if (compilationErrors.Any())
+        {
+            throw new InvalidOperationException(
+                "Failed to compile code." +
                 Environment.NewLine +
-                sourceCode;
+                string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))
-
-            // Parse the source code
-            var ast = SyntaxFactory.ParseSyntaxTree(
-                SourceText.From(sourceCodeWithUsings),
-                CSharpParseOptions.Default
             );
-
-            // Compile the code to IL
-            var compilation = CSharpCompilation.Create(
-                "CliFxTests_DynamicAssembly_" + Guid.NewGuid(),
-                new[] {ast},
-                new[]
-                {
-                    MetadataReference.CreateFromFile(Assembly.Load("netstandard").Location),
-                    MetadataReference.CreateFromFile(Assembly.Load("System.Runtime").Location),
-                    MetadataReference.CreateFromFile(typeof(object).Assembly.Location),
-                    MetadataReference.CreateFromFile(typeof(Console).Assembly.Location),
-                    MetadataReference.CreateFromFile(typeof(Enumerable).Assembly.Location),
-                    MetadataReference.CreateFromFile(typeof(DynamicCommandBuilder).Assembly.Location),
-                    MetadataReference.CreateFromFile(typeof(ICommand).Assembly.Location)
-                },
-                // DLL to avoid having to define the Main() method
-                new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
-            );
-
-            var compilationErrors = compilation
-                .GetDiagnostics()
-                .Where(d => d.Severity >= DiagnosticSeverity.Error)
-                .ToArray();
-
-            if (compilationErrors.Any())
-            {
-                throw new InvalidOperationException(
-                    "Failed to compile code." +
-                    Environment.NewLine +
-                    string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))
-                );
-            }
-
-            // Emit the code to an in-memory buffer
-            using var buffer = new MemoryStream();
-            var emit = compilation.Emit(buffer);
-
-            var emitErrors = emit
-                .Diagnostics
-                .Where(d => d.Severity >= DiagnosticSeverity.Error)
-                .ToArray();
-
-            if (emitErrors.Any())
-            {
-                throw new InvalidOperationException(
-                    "Failed to emit code." +
-                    Environment.NewLine +
-                    string.Join(Environment.NewLine, emitErrors.Select(e => e.ToString()))
-                );
-            }
-
-            // Load the generated assembly
-            var generatedAssembly = Assembly.Load(buffer.ToArray());
-
-            // Return all defined commands
-            var commandTypes = generatedAssembly
-                .GetTypes()
-                .Where(t => t.IsAssignableTo(typeof(ICommand)))
-                .ToArray();
-
-            if (commandTypes.Length <= 0)
-            {
-                throw new InvalidOperationException(
-                    "There are no command definitions in the provide source code."
-                );
-            }
-
-            return commandTypes;
         }
 
-        public static Type Compile(string sourceCode)
+        // Emit the code to an in-memory buffer
+        using var buffer = new MemoryStream();
+        var emit = compilation.Emit(buffer);
+
+        var emitErrors = emit
+            .Diagnostics
+            .Where(d => d.Severity >= DiagnosticSeverity.Error)
+            .ToArray();
+
+        if (emitErrors.Any())
         {
-            var commandTypes = CompileMany(sourceCode);
+            throw new InvalidOperationException(
-
+                "Failed to emit code." +
-            if (commandTypes.Count > 1)
+                Environment.NewLine +
-            {
+                string.Join(Environment.NewLine, emitErrors.Select(e => e.ToString()))
-                throw new InvalidOperationException(
+            );
-                    "There are more than one command definitions in the provide source code."
-                );
-            }
-
-            return commandTypes.Single();
         }
+
+        // Load the generated assembly
+        var generatedAssembly = Assembly.Load(buffer.ToArray());
+
+        // Return all defined commands
+        var commandTypes = generatedAssembly
+            .GetTypes()
+            .Where(t => t.IsAssignableTo(typeof(ICommand)) && !t.IsAbstract)
+            .ToArray();
+
+        if (commandTypes.Length <= 0)
+        {
+            throw new InvalidOperationException(
+                "There are no command definitions in the provided source code."
+            );
+        }
+
+        return commandTypes;
+    }
+
+    public static Type Compile(string sourceCode)
+    {
+        var commandTypes = CompileMany(sourceCode);
+
+        if (commandTypes.Count > 1)
+        {
+            throw new InvalidOperationException(
+                "There are more than one command definitions in the provided source code."
+            );
+        }
+
+        return commandTypes.Single();
     }
 }

CliFx.Tests/Utils/Extensions/AssertionExtensions.cs

@@ -1,54 +1,51 @@
 using System;
 using System.Collections.Generic;
 using FluentAssertions;
-using FluentAssertions.Collections;
 using FluentAssertions.Execution;
 using FluentAssertions.Primitives;
 
-namespace CliFx.Tests.Utils.Extensions
+namespace CliFx.Tests.Utils.Extensions;
+
+internal static class AssertionExtensions
 {
-    internal static class AssertionExtensions
+    public static void ConsistOfLines(
+        this StringAssertions assertions,
+        IEnumerable<string> lines)
     {
-        public static AndConstraint<StringCollectionAssertions> ConsistOfLines(
+        var actualLines = assertions.Subject.Split(new[] {'\n', '\r'}, StringSplitOptions.RemoveEmptyEntries);
-            this StringAssertions assertions,
+        actualLines.Should().Equal(lines);
-            IEnumerable<string> lines)
+    }
+
+    public static void ConsistOfLines(
+        this StringAssertions assertions,
+        params string[] lines) =>
+        assertions.ConsistOfLines((IEnumerable<string>) lines);
+
+    public static AndConstraint<StringAssertions> ContainAllInOrder(
+        this StringAssertions assertions,
+        IEnumerable<string> values)
+    {
+        var lastIndex = 0;
+
+        foreach (var value in values)
         {
-            var actualLines = assertions.Subject.Split(new[] {'\n', '\r'}, StringSplitOptions.RemoveEmptyEntries);
+            var index = assertions.Subject.IndexOf(value, lastIndex, StringComparison.Ordinal);
 
-            return actualLines.Should().Equal(lines);
+            if (index < 0)
-        }
-
-        public static AndConstraint<StringCollectionAssertions> ConsistOfLines(
-            this StringAssertions assertions,
-            params string[] lines) =>
-            assertions.ConsistOfLines((IEnumerable<string>) lines);
-
-        public static AndConstraint<StringAssertions> ContainAllInOrder(
-            this StringAssertions assertions,
-            IEnumerable<string> values)
-        {
-            var lastIndex = 0;
-
-            foreach (var value in values)
             {
-                var index = assertions.Subject.IndexOf(value, lastIndex, StringComparison.Ordinal);
+                Execute.Assertion.FailWith(
-
+                    $"Expected string '{assertions.Subject}' to contain '{value}' after position {lastIndex}."
-                if (index < 0)
+                );
-                {
-                    Execute.Assertion.FailWith(
-                        $"Expected string '{assertions.Subject}' to contain '{value}' after position {lastIndex}."
-                    );
-                }
-
-                lastIndex = index;
             }
 
-            return new(assertions);
+            lastIndex = index;
         }
 
-        public static AndConstraint<StringAssertions> ContainAllInOrder(
+        return new(assertions);
-            this StringAssertions assertions,
-            params string[] values) =>
-            assertions.ContainAllInOrder((IEnumerable<string>) values);
     }
+
+    public static AndConstraint<StringAssertions> ContainAllInOrder(
+        this StringAssertions assertions,
+        params string[] values) =>
+        assertions.ContainAllInOrder((IEnumerable<string>) values);
 }

CliFx.Tests/Utils/Extensions/ConsoleExtensions.cs

@@ -1,17 +1,16 @@
 using CliFx.Infrastructure;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests.Utils.Extensions
+namespace CliFx.Tests.Utils.Extensions;
-{
-    internal static class ConsoleExtensions
-    {
-        public static void DumpToTestOutput(this FakeInMemoryConsole console, ITestOutputHelper testOutputHelper)
-        {
-            testOutputHelper.WriteLine("[*] Captured standard output:");
-            testOutputHelper.WriteLine(console.ReadOutputString());
 
-            testOutputHelper.WriteLine("[*] Captured standard error:");
+internal static class ConsoleExtensions
-            testOutputHelper.WriteLine(console.ReadErrorString());
+{
-        }
+    public static void DumpToTestOutput(this FakeInMemoryConsole console, ITestOutputHelper testOutputHelper)
+    {
+        testOutputHelper.WriteLine("[*] Captured standard output:");
+        testOutputHelper.WriteLine(console.ReadOutputString());
+
+        testOutputHelper.WriteLine("[*] Captured standard error:");
+        testOutputHelper.WriteLine(console.ReadErrorString());
     }
 }

CliFx.Tests/Utils/NoOpCommand.cs

@@ -2,11 +2,10 @@
 using CliFx.Attributes;
 using CliFx.Infrastructure;
 
-namespace CliFx.Tests.Utils
+namespace CliFx.Tests.Utils;
+
+[Command]
+public class NoOpCommand : ICommand
 {
-    [Command]
+    public ValueTask ExecuteAsync(IConsole console) => default;
-    public class NoOpCommand : ICommand
-    {
-        public ValueTask ExecuteAsync(IConsole console) => default;
-    }
 }