Update version

Co-authored-by: Alexey Golub <tyrrrrrr@gmail.com>

.github/FUNDING.yml

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

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -0,0 +1,42 @@
+name: 🐞 Bug report
+description: Report broken functionality.
+labels: [bug]
+
+body:
+- type: markdown
+  attributes:
+    value: |
+      🧐 **Guidelines:**
+
+      - 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 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.
+    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 required to reproduce the bug.
+    placeholder: |
+      - Step 1
+      - Step 2
+      - Step 3
+  validations:
+    required: true

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - 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: Ask and answer questions.

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -0,0 +1,22 @@
+name: ✨ Feature request
+description: Request a new feature.
+labels: [enhancement]
+
+body:
+- type: markdown
+  attributes:
+    value: |
+      🧐 **Guidelines:**
+
+      - 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.
+  validations:
+    required: true

.github/workflows/CD.yml

@@ -1,27 +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 nuget locals all --clear
-          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

@@ -1,30 +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 nuget locals all --clear
-          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 +1,48 @@
+### 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.
+- Fixed an issue where help text tried to show default values for parameters and options whose type does not override `ToString()` method.
+- Fixed an issue where help text didn't show default values for parameters and options whose type is an enumerable of nullable enums. (Thanks [@Robert Dailey](https://github.com/rcdailey))
+- Fixed an issue where specific parts of the help text weren't legible in some terminals due to low color resolution. Removed the usage of `ConsoleColor.DarkGray` in help text.
+
+### v2.0.3 (09-Apr-2021)
+
+- Improved help text by showing valid values for non-scalar enum parameters and options. (Thanks [@Robert Dailey](https://github.com/rcdailey))
+
+### v2.0.2 (31-Mar-2021)
+
+- Fixed an issue where having a transitive reference to CliFx sometimes resulted in `SystemConsoleShouldBeAvoidedAnalyzer` throwing `NullReferenceException` during build.
+- Fixed some documentation typos and inconsistencies.
+
+### v2.0.1 (24-Mar-2021)
+
+- Fixed an issue where some exceptions with async stack traces generated on .NET 3.1 or earlier were not parsed and formatted correctly.
+- Fixed an issue where help text applied slightly incorrect formatting when displaying choices for enum-based parameters and properties.
+
 ### v2.0 (21-Mar-2021)
 
 > Note: this major release includes many breaking changes.

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

@@ -1,9 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
-    <IsPackable>false</IsPackable>
-    <IsTestProject>true</IsTestProject>
+    <TargetFramework>net6.0</TargetFramework>
     <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="Microsoft.NET.Test.Sdk" Version="16.9.1" />
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.4.0" />
-    <PackageReference Include="xunit" Version="2.4.0" />
+    <PackageReference Include="FluentAssertions" Version="6.3.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" />
+    <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
-{
-    public class CommandMustBeAnnotatedAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustBeAnnotatedAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_command_is_not_annotated_with_the_command_attribute()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class CommandMustBeAnnotatedAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustBeAnnotatedAnalyzer();
+
+    [Fact]
+    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
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_is_annotated_with_the_command_attribute()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_command_is_annotated_with_the_command_attribute()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public abstract class MyCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_is_implemented_as_an_abstract_class()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_command_is_implemented_as_an_abstract_class()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public abstract class MyCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class Foo
 {
     public int Bar { get; set; } = 5;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/CommandMustImplementInterfaceAnalyzerSpecs.cs

@@ -2,57 +2,56 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class CommandMustImplementInterfaceAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustImplementInterfaceAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_command_does_not_implement_ICommand_interface()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class CommandMustImplementInterfaceAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new CommandMustImplementInterfaceAnalyzer();
+
+    [Fact]
+    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
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_implements_ICommand_interface()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_command_implements_ICommand_interface()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_class_that_is_not_a_command()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class Foo
 {
     public int Bar { get; set; } = 5;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        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]
-        public void All_analyzers_have_unique_diagnostic_IDs()
-        {
-            // Arrange
-            var analyzers = typeof(AnalyzerBase)
-                .Assembly
-                .GetTypes()
-                .Where(t => !t.IsAbstract && t.IsAssignableTo(typeof(DiagnosticAnalyzer)))
-                .Select(t => (DiagnosticAnalyzer) Activator.CreateInstance(t)!)
-                .ToArray();
+        // Arrange
+        var analyzers = typeof(AnalyzerBase)
+            .Assembly
+            .GetTypes()
+            .Where(t => !t.IsAbstract && t.IsAssignableTo(typeof(DiagnosticAnalyzer)))
+            .Select(t => (DiagnosticAnalyzer) Activator.CreateInstance(t)!)
+            .ToArray();
 
-            // Act
-            var diagnosticIds = analyzers
-                .SelectMany(a => a.SupportedDiagnostics.Select(d => d.Id))
-                .ToArray();
+        // Act
+        var diagnosticIds = analyzers
+            .SelectMany(a => a.SupportedDiagnostics.Select(d => d.Id))
+            .ToArray();
 
-            // Assert
-            diagnosticIds.Should().OnlyHaveUniqueItems();
-        }
+        // Assert
+        diagnosticIds.Should().OnlyHaveUniqueItems();
     }
 }

CliFx.Analyzers.Tests/OptionMustBeInsideCommandAnalyzerSpecs.cs

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

CliFx.Analyzers.Tests/OptionMustHaveNameOrShortNameAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class OptionMustHaveNameOrShortNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveNameOrShortNameAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_an_option_does_not_have_a_name_or_short_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class OptionMustHaveNameOrShortNameAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveNameOrShortNameAnalyzer();
+
+    [Fact]
+    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
 {
@@ -23,16 +23,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -42,16 +42,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -61,16 +61,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -79,8 +79,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveUniqueNameAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class OptionMustHaveUniqueNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueNameAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_an_option_has_the_same_name_as_another_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class OptionMustHaveUniqueNameAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueNameAnalyzer();
+
+    [Fact]
+    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
 {
@@ -26,16 +26,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -48,16 +48,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -67,16 +67,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -85,8 +85,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveUniqueShortNameAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class OptionMustHaveUniqueShortNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueShortNameAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_an_option_has_the_same_short_name_as_another_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class OptionMustHaveUniqueShortNameAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveUniqueShortNameAnalyzer();
+
+    [Fact]
+    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
 {
@@ -26,16 +26,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_short_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_unique_short_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -48,16 +48,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name_which_is_unique_only_in_casing()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_short_name_which_is_unique_only_in_casing()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -70,16 +70,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -89,16 +89,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -107,8 +107,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidConverterAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class OptionMustHaveValidConverterAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidConverterAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_the_specified_option_converter_does_not_derive_from_BindingConverter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class OptionMustHaveValidConverterAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidConverterAnalyzer();
+
+    [Fact]
+    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;
@@ -28,16 +28,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_the_specified_option_converter_derives_from_BindingConverter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_the_specified_option_converter_derives_from_BindingConverter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyConverter : BindingConverter<string>
 {
     public override string Convert(string rawValue) => rawValue;
@@ -52,16 +52,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_converter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_converter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -71,16 +71,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidNameAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class OptionMustHaveValidNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidNameAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_an_option_has_a_name_which_is_too_short()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class OptionMustHaveValidNameAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidNameAnalyzer();
+
+    [Fact]
+    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
 {
@@ -23,16 +23,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_an_option_has_a_name_that_starts_with_a_non_letter_character()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_reports_an_error_if_an_option_has_a_name_that_starts_with_a_non_letter_character()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -42,16 +42,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -61,16 +61,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -80,16 +80,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -98,8 +98,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidShortNameAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class OptionMustHaveValidShortNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidShortNameAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        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 = @"
+public class OptionMustHaveValidShortNameAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidShortNameAnalyzer();
+
+    [Fact]
+    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
 {
@@ -23,16 +23,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_short_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_has_a_valid_short_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -42,16 +42,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_a_short_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -61,16 +61,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -79,8 +79,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/OptionMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class OptionMustHaveValidValidatorsAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidValidatorsAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        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 OptionMustHaveValidValidatorsAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustHaveValidValidatorsAnalyzer();
+
+    [Fact]
+    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) {}
@@ -28,16 +28,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_all_specified_option_validators_derive_from_BindingValidator()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_all_specified_option_validators_derive_from_BindingValidator()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyValidator : BindingValidator<string>
 {
     public override BindingValidationError Validate(string value) => Ok();
@@ -52,16 +52,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_validators()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_an_option_does_not_have_validators()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -71,16 +71,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_on_a_property_that_is_not_an_option()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/ParameterMustBeInsideCommandAnalyzerSpecs.cs

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

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class ParameterMustBeLastIfNonScalarAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeLastIfNonScalarAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_non_scalar_parameter_is_not_last_in_order()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class ParameterMustBeLastIfNonScalarAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeLastIfNonScalarAnalyzer();
+
+    [Fact]
+    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
 {
@@ -26,16 +26,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_non_scalar_parameter_is_last_in_order()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_non_scalar_parameter_is_the_last_in_order()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -48,16 +48,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -70,16 +70,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // 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 = @"
+    [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
 {
@@ -88,8 +88,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        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

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class ParameterMustBeSingleIfNonScalarAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeSingleIfNonScalarAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_more_than_one_non_scalar_parameters_are_defined()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class ParameterMustBeSingleIfNonScalarAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeSingleIfNonScalarAnalyzer();
+
+    [Fact]
+    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
 {
@@ -26,16 +26,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_only_one_non_scalar_parameter_is_defined()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_only_one_non_scalar_parameter_is_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -48,16 +48,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_no_non_scalar_parameters_are_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -70,16 +70,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // 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 = @"
+    [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
 {
@@ -88,8 +88,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveUniqueNameAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class ParameterMustHaveUniqueNameAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueNameAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_parameter_has_the_same_name_as_another_parameter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class ParameterMustHaveUniqueNameAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueNameAnalyzer();
+
+    [Fact]
+    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
 {
@@ -26,16 +26,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_name()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -48,16 +48,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // 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 = @"
+    [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
 {
@@ -66,8 +66,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveUniqueOrderAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class ParameterMustHaveUniqueOrderAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueOrderAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_parameter_has_the_same_order_as_another_parameter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class ParameterMustHaveUniqueOrderAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveUniqueOrderAnalyzer();
+
+    [Fact]
+    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
 {
@@ -26,16 +26,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_order()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_parameter_has_unique_order()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -48,16 +48,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // 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 = @"
+    [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
 {
@@ -66,8 +66,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveValidConverterAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class ParameterMustHaveValidConverterAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidConverterAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_the_specified_parameter_converter_does_not_derive_from_BindingConverter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class ParameterMustHaveValidConverterAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidConverterAnalyzer();
+
+    [Fact]
+    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;
@@ -28,16 +28,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_the_specified_parameter_converter_derives_from_BindingConverter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_the_specified_parameter_converter_derives_from_BindingConverter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyConverter : BindingConverter<string>
 {
     public override string Convert(string rawValue) => rawValue;
@@ -52,16 +52,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_a_converter()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_a_converter()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -71,16 +71,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // 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 = @"
+    [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
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/ParameterMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class ParameterMustHaveValidValidatorsAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidValidatorsAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        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 ParameterMustHaveValidValidatorsAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustHaveValidValidatorsAnalyzer();
+
+    [Fact]
+    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) {}
@@ -28,16 +28,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_all_specified_parameter_validators_derive_from_BindingValidator()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_all_specified_parameter_validators_derive_from_BindingValidator()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 public class MyValidator : BindingValidator<string>
 {
     public override BindingValidationError Validate(string value) => Ok();
@@ -52,16 +52,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_validators()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_parameter_does_not_have_validators()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -71,16 +71,16 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // 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 = @"
+    [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
 {
@@ -89,8 +89,7 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
     }
 }

CliFx.Analyzers.Tests/SystemConsoleShouldBeAvoidedAnalyzerSpecs.cs

@@ -2,18 +2,18 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
-namespace CliFx.Analyzers.Tests
-{
-    public class SystemConsoleShouldBeAvoidedAnalyzerSpecs
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new SystemConsoleShouldBeAvoidedAnalyzer();
+namespace CliFx.Analyzers.Tests;
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_command_calls_a_method_on_SystemConsole()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+public class SystemConsoleShouldBeAvoidedAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new SystemConsoleShouldBeAvoidedAnalyzer();
+
+    [Fact]
+    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
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_command_accesses_a_property_on_SystemConsole()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_reports_an_error_if_a_command_accesses_a_property_on_SystemConsole()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -43,16 +43,16 @@ public class MyCommand : ICommand
         return default;
     }
 }";
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_reports_an_error_if_a_command_calls_a_method_on_a_property_of_SystemConsole()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_reports_an_error_if_a_command_calls_a_method_on_a_property_of_SystemConsole()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -63,16 +63,16 @@ public class MyCommand : ICommand
     }
 }";
 
-            // Act & assert
-            Analyzer.Should().ProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_a_command_interacts_with_the_console_through_IConsole()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_command_interacts_with_the_console_through_IConsole()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -83,16 +83,16 @@ public class MyCommand : ICommand
     }
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
 
-        [Fact]
-        public void Analyzer_does_not_report_an_error_if_IConsole_is_not_available_in_the_current_method()
-        {
-            // Arrange
-            // language=cs
-            const string code = @"
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_IConsole_is_not_available_in_the_current_method()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
 [Command]
 public class MyCommand : ICommand
 {
@@ -101,8 +101,26 @@ public class MyCommand : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }";
 
-            // Act & assert
-            Analyzer.Should().NotProduceDiagnostics(code);
-        }
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_command_does_not_access_SystemConsole()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        return default;
+    }
+}";
+
+        // Act & assert
+        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
-{
-    internal class AnalyzerAssertions : ReferenceTypeAssertions<DiagnosticAnalyzer, AnalyzerAssertions>
-    {
-        protected override string Identifier { get; } = "analyzer";
+namespace CliFx.Analyzers.Tests.Utils;
 
-        public AnalyzerAssertions(DiagnosticAnalyzer analyzer)
-            : base(analyzer)
+internal class AnalyzerAssertions : ReferenceTypeAssertions<DiagnosticAnalyzer, AnalyzerAssertions>
+{
+    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 defaultSystemNamespaces = new[]
+            var buffer = new StringBuilder();
+
+            buffer.AppendLine("Expected and produced diagnostics do not match.");
+            buffer.AppendLine();
+
+            buffer.AppendLine("Expected diagnostics:");
+
+            foreach (var expectedDiagnostic in expectedDiagnostics)
             {
-                "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},
-                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()))
-                );
+                buffer.Append("  - ");
+                buffer.Append(expectedDiagnostic.Id);
+                buffer.AppendLine();
             }
 
-            return compilation;
-        }
+            buffer.AppendLine();
 
-        private IReadOnlyList<Diagnostic> GetProducedDiagnostics(string sourceCode)
-        {
-            var analyzers = ImmutableArray.Create(Subject);
-            var compilation = Compile(sourceCode);
+            buffer.AppendLine("Produced diagnostics:");
 
-            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(() =>
+            foreach (var producedDiagnostic in producedDiagnostics)
             {
-                var buffer = new StringBuilder();
+                buffer.Append("  - ");
+                buffer.Append(producedDiagnostic);
+            }
 
-                buffer.AppendLine("Expected and produced diagnostics do not match.");
-                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());
-            });
-        }
+            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(
-            string diagnosticTitle,
-            string diagnosticMessage,
-            DiagnosticSeverity diagnosticSeverity = DiagnosticSeverity.Error)
-        {
-            SupportedDiagnostic = new DiagnosticDescriptor(
-                "CliFx_" + GetType().Name.TrimEnd("Analyzer"),
-                diagnosticTitle,
-                diagnosticMessage,
-                "CliFx",
-                diagnosticSeverity,
-                true
-            );
+    protected Diagnostic CreateDiagnostic(Location location) =>
+        Diagnostic.Create(SupportedDiagnostic, location);
 
-            SupportedDiagnostics = ImmutableArray.Create(SupportedDiagnostic);
-        }
-
-        protected Diagnostic CreateDiagnostic(Location location) =>
-            Diagnostic.Create(SupportedDiagnostic, location);
-
-        public override void Initialize(AnalysisContext context)
-        {
-            context.EnableConcurrentExecution();
-            context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
-        }
+    public override void Initialize(AnalysisContext context)
+    {
+        context.EnableConcurrentExecution();
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
     }
 }

CliFx.Analyzers/CliFx.Analyzers.csproj

@@ -7,7 +7,7 @@
   </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 class CommandMustBeAnnotatedAnalyzer : AnalyzerBase
+    public CommandMustBeAnnotatedAnalyzer()
+        : 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}`",
-                $"This type must be annotated with `{SymbolNames.CliFxCommandAttribute}` in order to be a valid command.")
+    }
+
+    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)
         {
-        }
-
-        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);
+            context.ReportDiagnostic(CreateDiagnostic(classDeclaration.GetLocation()));
         }
     }
+
+    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 class CommandMustImplementInterfaceAnalyzer : AnalyzerBase
+    public CommandMustImplementInterfaceAnalyzer()
+        : 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",
-                $"This type must implement `{SymbolNames.CliFxCommandInterface}` interface in order to be a valid command.")
+    }
+
+    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)
         {
-        }
-
-        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);
+            context.ReportDiagnostic(CreateDiagnostic(classDeclaration.GetLocation()));
         }
     }
+
+    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; }
-
-        public char? ShortName { get; }
-
-        public ITypeSymbol? ConverterType { get; }
-
-        public IReadOnlyList<ITypeSymbol> ValidatorTypes { get; }
-
-        public CommandOptionSymbol(
-            string? name,
-            char? shortName,
-            ITypeSymbol? converterType,
-            IReadOnlyList<ITypeSymbol> validatorTypes)
-        {
-            Name = name;
-            ShortName = shortName;
-            ConverterType = converterType;
-            ValidatorTypes = validatorTypes;
-        }
-    }
-
-    internal partial class CommandOptionSymbol
-    {
-        private static AttributeData? TryGetOptionAttribute(IPropertySymbol property) =>
-            property
-                .GetAttributes()
-                .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandOptionAttribute));
-
-        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;
-
-            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;
+        Name = name;
+        ShortName = shortName;
+        ConverterType = converterType;
+        ValidatorTypes = validatorTypes;
     }
 }
+
+internal partial class CommandOptionSymbol
+{
+    private static AttributeData? TryGetOptionAttribute(IPropertySymbol property) =>
+        property
+            .GetAttributes()
+            .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandOptionAttribute));
+
+    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;
+
+        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);
+
+        return attribute is not null
+            ? FromAttribute(attribute)
+            : 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; }
-
-        public string? Name { get; }
-
-        public ITypeSymbol? ConverterType { get; }
-
-        public IReadOnlyList<ITypeSymbol> ValidatorTypes { get; }
-
-        public CommandParameterSymbol(
-            int order,
-            string? name,
-            ITypeSymbol? converterType,
-            IReadOnlyList<ITypeSymbol> validatorTypes)
-        {
-            Order = order;
-            Name = name;
-            ConverterType = converterType;
-            ValidatorTypes = validatorTypes;
-        }
-    }
-
-    internal partial class CommandParameterSymbol
-    {
-        private static AttributeData? TryGetParameterAttribute(IPropertySymbol property) =>
-            property
-                .GetAttributes()
-                .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandParameterAttribute));
-
-        private static CommandParameterSymbol FromAttribute(AttributeData attribute)
-        {
-            var order = (int) attribute
-                .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;
+        Order = order;
+        Name = name;
+        IsRequired = isRequired;
+        ConverterType = converterType;
+        ValidatorTypes = validatorTypes;
     }
 }
+
+internal partial class CommandParameterSymbol
+{
+    private static AttributeData? TryGetParameterAttribute(IPropertySymbol property) =>
+        property
+            .GetAttributes()
+            .FirstOrDefault(a => a.AttributeClass.DisplayNameMatches(SymbolNames.CliFxCommandParameterAttribute));
+
+    private static CommandParameterSymbol FromAttribute(AttributeData attribute)
+    {
+        var order = (int)attribute
+            .ConstructorArguments
+            .Select(a => a.Value)
+            .First()!;
+
+        var name = attribute
+            .NamedArguments
+            .Where(a => a.Key == "Name")
+            .Select(a => a.Value.Value)
+            .FirstOrDefault() as string;
+
+        var isRequired = attribute
+            .NamedArguments
+            .Where(a => a.Key == "IsRequired")
+            .Select(a => a.Value.Value)
+            .FirstOrDefault() as bool?;
+
+        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, isRequired, converter, validators);
+    }
+
+    public static CommandParameterSymbol? TryResolve(IPropertySymbol property)
+    {
+        var attribute = TryGetParameterAttribute(property);
+
+        return attribute is not null
+            ? FromAttribute(attribute)
+            : 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 CliFxCommandParameterAttribute = "CliFx.Attributes.CommandParameterAttribute";
-        public const string CliFxCommandOptionAttribute = "CliFx.Attributes.CommandOptionAttribute";
-        public const string CliFxConsoleInterface = "CliFx.Infrastructure.IConsole";
-        public const string CliFxBindingConverterInterface = "CliFx.Extensibility.IBindingConverter";
-        public const string CliFxBindingConverterClass = "CliFx.Extensibility.BindingConverter<T>";
-        public const string CliFxBindingValidatorInterface = "CliFx.Extensibility.IBindingValidator";
-        public const string CliFxBindingValidatorClass = "CliFx.Extensibility.BindingValidator<T>";
-    }
+    public const string CliFxCommandInterface = "CliFx.ICommand";
+    public const string CliFxCommandAttribute = "CliFx.Attributes.CommandAttribute";
+    public const string CliFxCommandParameterAttribute = "CliFx.Attributes.CommandParameterAttribute";
+    public const string CliFxCommandOptionAttribute = "CliFx.Attributes.CommandOptionAttribute";
+    public const string CliFxConsoleInterface = "CliFx.Infrastructure.IConsole";
+    public const string CliFxBindingConverterInterface = "CliFx.Extensibility.IBindingConverter";
+    public const string CliFxBindingConverterClass = "CliFx.Extensibility.BindingConverter<T>";
+    public const string CliFxBindingValidatorInterface = "CliFx.Extensibility.IBindingValidator";
+    public const string CliFxBindingValidatorClass = "CliFx.Extensibility.BindingValidator<T>";
 }

CliFx.Analyzers/OptionMustBeInsideCommandAnalyzer.cs

@@ -5,44 +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 class OptionMustBeInsideCommandAnalyzer : AnalyzerBase
+    public OptionMustBeInsideCommandAnalyzer()
+        : 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",
-                $"This option must be defined inside a class that implements `{SymbolNames.CliFxCommandInterface}`.")
+    }
+
+    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)
         {
-        }
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            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);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
         }
     }
+
+    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 class OptionMustHaveNameOrShortNameAnalyzer : AnalyzerBase
+    public OptionMustHaveNameOrShortNameAnalyzer()
+        : 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(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
-                return;
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            return;
 
-            if (string.IsNullOrWhiteSpace(option.Name) && option.ShortName is null)
-            {
-                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
+        if (string.IsNullOrWhiteSpace(option.Name) && option.ShortName is null)
         {
-            base.Initialize(context);
-            context.HandlePropertyDeclaration(Analyze);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
 }

CliFx.Analyzers/OptionMustHaveUniqueNameAnalyzer.cs

@@ -6,57 +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 class OptionMustHaveUniqueNameAnalyzer : AnalyzerBase
+    public OptionMustHaveUniqueNameAnalyzer()
+        : 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",
-                "This option's name must be unique within the command (comparison IS NOT case sensitive).")
+    }
+
+    private void Analyze(
+        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(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
-                return;
+            if (string.IsNullOrWhiteSpace(otherOption.Name))
+                continue;
 
-            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)
+            if (string.Equals(option.Name, otherOption.Name, StringComparison.OrdinalIgnoreCase))
             {
-                var otherOption = CommandOptionSymbol.TryResolve(otherProperty);
-                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()));
-                }
+                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/OptionMustHaveUniqueShortNameAnalyzer.cs

@@ -5,57 +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 class OptionMustHaveUniqueShortNameAnalyzer : AnalyzerBase
+    public OptionMustHaveUniqueShortNameAnalyzer()
+        : 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",
-                "This option's short name must be unique within the command (comparison IS case sensitive).")
+    }
+
+    private void Analyze(
+        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(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
-                return;
+            if (otherOption.ShortName is null)
+                continue;
 
-            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)
+            if (option.ShortName == otherOption.ShortName)
             {
-                var otherOption = CommandOptionSymbol.TryResolve(otherProperty);
-                if (otherOption is null)
-                    continue;
-
-                if (otherOption.ShortName is null)
-                    continue;
-
-                if (option.ShortName == otherOption.ShortName)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
+                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/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 class OptionMustHaveValidConverterAnalyzer : AnalyzerBase
+    public OptionMustHaveValidConverterAnalyzer()
+        : 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}`",
-                $"Converter specified for this option must derive from `{SymbolNames.CliFxBindingConverterClass}`.")
+    }
+
+    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)
         {
-        }
-
-        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);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
         }
     }
+
+    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 class OptionMustHaveValidNameAnalyzer : AnalyzerBase
+    public OptionMustHaveValidNameAnalyzer()
+        : 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",
-                "This option's name must be at least 2 characters long and must start with a letter.")
+    }
+
+    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]))
         {
-        }
-
-        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);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
         }
     }
+
+    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 class OptionMustHaveValidShortNameAnalyzer : AnalyzerBase
+    public OptionMustHaveValidShortNameAnalyzer()
+        : 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",
-                "This option's short name must be a single letter character.")
+    }
+
+    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))
         {
-        }
-
-        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);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
         }
     }
+
+    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 class OptionMustHaveValidValidatorsAnalyzer : AnalyzerBase
+    public OptionMustHaveValidValidatorsAnalyzer()
+        : 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(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var option = CommandOptionSymbol.TryResolve(property);
-            if (option is null)
-                return;
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            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
-                var validatorImplementsInterface = validatorType
-                    .AllInterfaces
-                    .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingValidatorInterface));
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
 
-                if (!validatorImplementsInterface)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-                    // No need to report multiple identical diagnostics on the same node
-                    break;
-                }
+                // No need to report multiple identical diagnostics on the same node
+                break;
             }
         }
+    }
 
-        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/ParameterMustBeInsideCommandAnalyzer.cs

@@ -5,44 +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 class ParameterMustBeInsideCommandAnalyzer : AnalyzerBase
+    public ParameterMustBeInsideCommandAnalyzer()
+        : 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",
-                $"This parameter must be defined inside a class that implements `{SymbolNames.CliFxCommandInterface}`.")
+    }
+
+    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)
         {
-        }
-
-        private void Analyze(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            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);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
         }
     }
+
+    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

@@ -5,61 +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 class ParameterMustBeLastIfNonScalarAnalyzer : AnalyzerBase
+    public ParameterMustBeLastIfNonScalarAnalyzer()
+        : 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",
-                "This parameter has a non-scalar type so it must be last in order (its order must be highest within the command).")
+    }
+
+    private static bool IsScalar(ITypeSymbol 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 (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) =>
-            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 (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)
+            if (otherParameter.Order > parameter.Order)
             {
-                var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
-                if (otherParameter is null)
-                    continue;
-
-                if (otherParameter.Order > parameter.Order)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
+                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/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

@@ -5,59 +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 class ParameterMustBeSingleIfNonScalarAnalyzer : AnalyzerBase
+    public ParameterMustBeSingleIfNonScalarAnalyzer()
+        : 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",
-                "This parameter has a non-scalar type so it must be the only such parameter in the command.")
+    }
+
+    private static bool IsScalar(ITypeSymbol 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))
+                continue;
 
-        private static bool IsScalar(ITypeSymbol 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 (!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 (!IsScalar(otherProperty.Type))
             {
-                if (!CommandParameterSymbol.IsParameterProperty(otherProperty))
-                    continue;
-
-                if (!IsScalar(otherProperty.Type))
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
+                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/ParameterMustHaveUniqueNameAnalyzer.cs

@@ -6,57 +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 class ParameterMustHaveUniqueNameAnalyzer : AnalyzerBase
+    public ParameterMustHaveUniqueNameAnalyzer()
+        : 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",
-                "This parameter's name must be unique within the command (comparison IS NOT case sensitive).")
+    }
+
+    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 (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(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var parameter = CommandParameterSymbol.TryResolve(property);
-            if (parameter is null)
-                return;
+            if (string.IsNullOrWhiteSpace(otherParameter.Name))
+                continue;
 
-            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)
+            if (string.Equals(parameter.Name, otherParameter.Name, StringComparison.OrdinalIgnoreCase))
             {
-                var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
-                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()));
-                }
+                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/ParameterMustHaveUniqueOrderAnalyzer.cs

@@ -5,51 +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 class ParameterMustHaveUniqueOrderAnalyzer : AnalyzerBase
+    public ParameterMustHaveUniqueOrderAnalyzer()
+        : base(
+            "Parameters must have unique order",
+            "This parameter's order must be unique within the command.")
     {
-        public ParameterMustHaveUniqueOrderAnalyzer()
-            : base(
-                "Parameters must have unique order",
-                "This parameter's order must be unique 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;
+
+        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(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            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)
+            if (parameter.Order == otherParameter.Order)
             {
-                var otherParameter = CommandParameterSymbol.TryResolve(otherProperty);
-                if (otherParameter is null)
-                    continue;
-
-                if (parameter.Order == otherParameter.Order)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-                }
+                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/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 class ParameterMustHaveValidConverterAnalyzer : AnalyzerBase
+    public ParameterMustHaveValidConverterAnalyzer()
+        : 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}`",
-                $"Converter specified for this parameter must derive from `{SymbolNames.CliFxBindingConverterClass}`.")
+    }
+
+    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)
         {
-        }
-
-        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);
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
         }
     }
+
+    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 class ParameterMustHaveValidValidatorsAnalyzer : AnalyzerBase
+    public ParameterMustHaveValidValidatorsAnalyzer()
+        : 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(
-            SyntaxNodeAnalysisContext context,
-            PropertyDeclarationSyntax propertyDeclaration,
-            IPropertySymbol property)
-        {
-            var parameter = CommandParameterSymbol.TryResolve(property);
-            if (parameter is null)
-                return;
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            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
-                var validatorImplementsInterface = validatorType
-                    .AllInterfaces
-                    .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingValidatorInterface));
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
 
-                if (!validatorImplementsInterface)
-                {
-                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
-
-                    // No need to report multiple identical diagnostics on the same node
-                    break;
-                }
+                // No need to report multiple identical diagnostics on the same node
+                break;
             }
         }
+    }
 
-        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/SystemConsoleShouldBeAvoidedAnalyzer.cs

@@ -6,72 +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 class SystemConsoleShouldBeAvoidedAnalyzer : AnalyzerBase
+    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)
     {
-        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(
-            SyntaxNodeAnalysisContext context,
-            SyntaxNode node)
-        {
-            var currentNode = node;
+    private MemberAccessExpressionSyntax? TryGetSystemConsoleMemberAccess(
+        SyntaxNodeAnalysisContext context,
+        SyntaxNode 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 symbol = context.SemanticModel.GetSymbolInfo(memberAccess).Symbol;
-
-                if (symbol is not null && symbol.ContainingType.DisplayNameMatches("System.Console"))
-                {
-                    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 memberAccess;
             }
 
-            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,
-            // 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);
+            context.ReportDiagnostic(CreateDiagnostic(systemConsoleMemberAccess.GetLocation()));
         }
     }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.SimpleMemberAccessExpression);
+    }
 }

CliFx.Analyzers/Utils/Extensions/RoslynExtensions.cs

@@ -4,45 +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) =>
-            string.Equals(symbol.ToDisplayString(), name, StringComparison.Ordinal);
-
-        public static void HandleClassDeclaration(
-            this AnalysisContext analysisContext,
-            Action<SyntaxNodeAnalysisContext, ClassDeclarationSyntax, ITypeSymbol> handler)
+        analysisContext.RegisterSyntaxNodeAction(ctx =>
         {
-            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);
-                if (type is null)
-                    return;
+            var type = ctx.SemanticModel.GetDeclaredSymbol(classDeclaration);
+            if (type is null)
+                return;
 
-                handler(ctx, classDeclaration, type);
-            }, SyntaxKind.ClassDeclaration);
-        }
+            analyze(ctx, classDeclaration, type);
+        }, SyntaxKind.ClassDeclaration);
+    }
 
-        public static void HandlePropertyDeclaration(
-            this AnalysisContext analysisContext,
-            Action<SyntaxNodeAnalysisContext, PropertyDeclarationSyntax, IPropertySymbol> handler)
+    public static void HandlePropertyDeclaration(
+        this AnalysisContext analysisContext,
+        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);
-                if (property is null)
-                    return;
+            var property = ctx.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
+            if (property is null)
+                return;
 
-                handler(ctx, propertyDeclaration, property);
-            }, SyntaxKind.PropertyDeclaration);
-        }
+            analyze(ctx, propertyDeclaration, property);
+        }, SyntaxKind.PropertyDeclaration);
     }
 }

CliFx.Analyzers/Utils/Extensions/StringExtensions.cs

@@ -1,18 +1,17 @@
 using System;
 
-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);
+namespace CliFx.Analyzers.Utils.Extensions;
 
-            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]
-        public class CliFxCommand : ICommand
-        {
-            [CommandOption("str", 's')]
-            public string? StrOption { get; set; }
+        [CommandOption("str", 's')]
+        public string? StrOption { get; set; }
 
-            [CommandOption("int", 'i')]
-            public int IntOption { get; set; }
+        [CommandOption("int", 'i')]
+        public int IntOption { get; set; }
 
-            [CommandOption("bool", 'b')]
-            public bool BoolOption { get; set; }
+        [CommandOption("bool", 'b')]
+        public bool BoolOption { get; set; }
 
-            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>());
+        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>());
 }

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
-{
-    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)
-            {
-            }
-        }
+namespace CliFx.Benchmarks;
 
-        [Benchmark(Description = "Cocona")]
-        public void ExecuteWithCocona() => CoconaApp.Run<CoconaCommand>(Arguments);
+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 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")]
-            public int IntOption { get; set; }
+        [Option("--int|-i")]
+        public int IntOption { get; set; }
 
-            [Option("--bool|-b")]
-            public bool BoolOption { get; set; }
+        [Option("--bool|-b")]
+        public bool BoolOption { get; set; }
 
-            public int OnExecute() => 0;
-        }
-
-        [Benchmark(Description = "McMaster.Extensions.CommandLineUtils")]
-        public int ExecuteWithMcMaster() => CommandLineApplication.Execute<McMasterCommand>(Arguments);
+        public int OnExecute() => 0;
     }
+
+    [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;
-
-            public Task<int> ExecuteAsync(string[] args)
+            var command = new RootCommand
             {
-                var command = new RootCommand
+                new Option(new[] {"--str", "-s"})
                 {
-                    new Option(new[] {"--str", "-s"})
-                    {
-                        Argument = new Argument<string?>()
-                    },
-                    new Option(new[] {"--int", "-i"})
-                    {
-                        Argument = new Argument<int>()
-                    },
-                    new Option(new[] {"--bool", "-b"})
-                    {
-                        Argument = new Argument<bool>()
-                    }
-                };
+                    Argument = new Argument<string?>()
+                },
+                new Option(new[] {"--int", "-i"})
+                {
+                    Argument = new Argument<int>()
+                },
+                new Option(new[] {"--bool", "-b"})
+                {
+                    Argument = new Argument<bool>()
+                }
+            };
 
-                command.Handler = CommandHandler.Create(
-                    typeof(SystemCommandLineCommand).GetMethod(nameof(ExecuteHandler))!
-                );
+            command.Handler = CommandHandler.Create(
+                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
-{
-    [RankColumn]
-    [Orderer(SummaryOrderPolicy.FastestToSlowest)]
-    public partial class Benchmarks
-    {
-        private static readonly string[] Arguments = {"--str", "hello world", "-i", "13", "-b"};
+namespace CliFx.Benchmarks;
 
-        public static void Main() => BenchmarkRunner.Run<Benchmarks>(
-            DefaultConfig
-                .Instance
-                .With(ConfigOptions.DisableOptimizationsValidator)
-        );
-    }
+[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>(
+        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="0.12.0" />
+    <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

@@ -2,12 +2,12 @@
 
   <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="Newtonsoft.Json" Version="12.0.3" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
   </ItemGroup>
 
   <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.")]
-    public partial class BookAddCommand : ICommand
+    private readonly 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)
     {
-        private readonly 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;
-        }
+        _libraryProvider = libraryProvider;
     }
 
-    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(
-            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
-        );
+        var book = new Book(Title, Author, Published, Isbn);
+        _libraryProvider.AddBook(book);
 
-        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)
-        );
+        console.Output.WriteLine("Book added.");
+        console.Output.WriteBook(book);
+
+        return default;
     }
 }
+
+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.")]
-    public class BookCommand : ICommand
+    private readonly LibraryProvider _libraryProvider;
+
+    [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 string Title { get; init; } = "";
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        var book = _libraryProvider.TryGetBook(Title);
 
-        public BookCommand(LibraryProvider libraryProvider)
-        {
-            _libraryProvider = libraryProvider;
-        }
+        if (book is null)
+            throw new CommandException("Book not found.", 10);
 
-        public ValueTask ExecuteAsync(IConsole console)
-        {
-            var book = _libraryProvider.TryGetBook(Title);
+        console.Output.WriteBook(book);
 
-            if (book is null)
-                throw new CommandException("Book not found.", 10);
-
-            console.Output.WriteBook(book);
-
-            return default;
-        }
+        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.")]
-    public class BookListCommand : ICommand
+    private readonly LibraryProvider _libraryProvider;
+
+    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)
-        {
-            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;
-        }
+        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.")]
-    public class BookRemoveCommand : ICommand
+    private readonly LibraryProvider _libraryProvider;
+
+    [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 string Title { get; init; } = "";
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        var book = _libraryProvider.TryGetBook(Title);
 
-        public BookRemoveCommand(LibraryProvider libraryProvider)
-        {
-            _libraryProvider = libraryProvider;
-        }
+        if (book is null)
+            throw new CommandException("Book not found.", 10);
 
-        public ValueTask ExecuteAsync(IConsole console)
-        {
-            var book = _libraryProvider.TryGetBook(Title);
+        _libraryProvider.RemoveBook(book);
 
-            if (book is null)
-                throw new CommandException("Book not found.", 10);
+        console.Output.WriteLine($"Book {Title} removed.");
 
-            _libraryProvider.RemoveBook(book);
-
-            console.Output.WriteLine($"Book {Title} removed.");
-
-            return default;
-        }
+        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; }
-
-        public string Author { get; }
-
-        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;
-        }
+        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; }
-
-        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)
-        {
-            EanPrefix = eanPrefix;
-            RegistrationGroup = registrationGroup;
-            Registrant = registrant;
-            Publication = publication;
-            CheckDigit = checkDigit;
-        }
-
-        public override string ToString() =>
-            $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
+        EanPrefix = eanPrefix;
+        RegistrationGroup = registrationGroup;
+        Registrant = registrant;
+        Publication = publication;
+        CheckDigit = checkDigit;
     }
 
-    public partial class Isbn
-    {
-        public static Isbn Parse(string value, IFormatProvider formatProvider)
-        {
-            var components = value.Split('-', 5, StringSplitOptions.RemoveEmptyEntries);
+    public override string ToString() =>
+        $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
+}
 
-            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)
-            );
-        }
+public partial class Isbn
+{
+    public static Isbn Parse(string value, IFormatProvider formatProvider)
+    {
+        var components = value.Split('-', 5, StringSplitOptions.RemoveEmptyEntries);
+
+        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; }
-
-        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);
-        }
+        Books = 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)
-        {
-            var data = JsonConvert.SerializeObject(library);
-            File.WriteAllText(StorageFilePath, data);
-        }
+    public Library GetLibrary()
+    {
+        if (!File.Exists(StorageFilePath))
+            return Library.Empty;
 
-        public Library GetLibrary()
-        {
-            if (!File.Exists(StorageFilePath))
-                return Library.Empty;
+        var data = File.ReadAllText(StorageFilePath);
 
-            var data = File.ReadAllText(StorageFilePath);
+        return JsonConvert.DeserializeObject<Library>(data) ?? Library.Empty;
+    }
 
-            return JsonConvert.DeserializeObject<Library>(data);
-        }
+    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)
-        {
-            var updatedLibrary = GetLibrary().WithBook(book);
-            StoreLibrary(updatedLibrary);
-        }
-
-        public void RemoveBook(Book book)
-        {
-            var updatedLibrary = GetLibrary().WithoutBook(book);
-            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 System.Threading.Tasks;
+using CliFx;
 using CliFx.Demo.Commands;
 using CliFx.Demo.Domain;
 using Microsoft.Extensions.DependencyInjection;
 
-namespace CliFx.Demo
-{
-    public static class Program
-    {
-        private static IServiceProvider GetServiceProvider()
-        {
-            // We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
-            var services = new ServiceCollection();
+// We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
+var services = new ServiceCollection();
 
-            // Register services
-            services.AddSingleton<LibraryProvider>();
+// Register services
+services.AddSingleton<LibraryProvider>();
 
-            // Register commands
-            services.AddTransient<BookCommand>();
-            services.AddTransient<BookAddCommand>();
-            services.AddTransient<BookRemoveCommand>();
-            services.AddTransient<BookListCommand>();
+// Register commands
+services.AddTransient<BookCommand>();
+services.AddTransient<BookAddCommand>();
+services.AddTransient<BookRemoveCommand>();
+services.AddTransient<BookListCommand>();
 
-            return services.BuildServiceProvider();
-        }
+var serviceProvider = services.BuildServiceProvider();
 
-        public static async Task<int> Main() =>
-            await new CliApplicationBuilder()
-                .SetDescription("Demo application showcasing CliFx features.")
-                .AddCommandsFromThisAssembly()
-                .UseTypeActivator(GetServiceProvider().GetRequiredService)
-                .Build()
-                .RunAsync();
-    }
-}
+return await new CliApplicationBuilder()
+    .SetDescription("Demo application showcasing CliFx features.")
+    .AddCommandsFromThisAssembly()
+    .UseTypeActivator(serviceProvider.GetRequiredService)
+    .Build()
+    .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))
-                writer.WriteLine(book.Title);
+        // Title
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Title);
 
-            // Author
-            writer.Write("  ");
-            writer.Write("Author: ");
+        // Author
+        writer.Write("  ");
+        writer.Write("Author: ");
 
-            using (writer.Console.WithForegroundColor(ConsoleColor.White))
-                writer.WriteLine(book.Author);
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Author);
 
-            // Published
-            writer.Write("  ");
-            writer.Write("Published: ");
+        // Published
+        writer.Write("  ");
+        writer.Write("Published: ");
 
-            using (writer.Console.WithForegroundColor(ConsoleColor.White))
-                writer.WriteLine($"{book.Published:d}");
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine($"{book.Published:d}");
 
-            // ISBN
-            writer.Write("  ");
-            writer.Write("ISBN: ");
+        // ISBN
+        writer.Write("  ");
+        writer.Write("ISBN: ");
 
-            using (writer.Console.WithForegroundColor(ConsoleColor.White))
-                writer.WriteLine(book.Isbn);
-        }
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            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 class ConsoleTestCommand : ICommand
+    public ValueTask ExecuteAsync(IConsole console)
     {
-        public ValueTask ExecuteAsync(IConsole console)
+        var input = console.Input.ReadToEnd();
+
+        using (console.WithColors(ConsoleColor.Black, ConsoleColor.White))
         {
-            var input = console.Input.ReadToEnd();
-
-            using (console.WithColors(ConsoleColor.Black, ConsoleColor.White))
-            {
-                console.Output.WriteLine(input);
-                console.Error.WriteLine(input);
-            }
-
-            return default;
+            console.Output.WriteLine(input);
+            console.Error.WriteLine(input);
         }
+
+        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")]
-    public class EnvironmentTestCommand : ICommand
+    [CommandOption("target", EnvironmentVariable = "ENV_TARGET")]
+    public string GreetingTarget { get; set; } = "World";
+
+    public ValueTask ExecuteAsync(IConsole console)
     {
-        [CommandOption("target", EnvironmentVariable = "ENV_TARGET")]
-        public string GreetingTarget { get; set; } = "World";
+        console.Output.WriteLine($"Hello {GreetingTarget}!");
 
-        public ValueTask ExecuteAsync(IConsole console)
-        {
-            console.Output.WriteLine($"Hello {GreetingTarget}!");
-
-            return default;
-        }
+        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
-    // that require an external process to properly verify.
+    public static Assembly Assembly { get; } = typeof(Program).Assembly;
 
-    public static partial class Program
-    {
-        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() =>
-            await new CliApplicationBuilder()
-                .AddCommandsFromThisAssembly()
-                .Build()
-                .RunAsync();
-    }
+    public static string Location { get; } = Assembly.Location;
+}
+
+public static partial class Program
+{
+    public static async Task Main() =>
+        await new CliApplicationBuilder()
+            .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]
-        public async Task Application_can_be_created_with_minimal_configuration()
-        {
-            // Act
-            var app = new CliApplicationBuilder()
-                .AddCommandsFromThisAssembly()
-                .UseConsole(FakeConsole)
-                .Build();
+    [Fact]
+    public async Task Application_can_be_created_with_minimal_configuration()
+    {
+        // Act
+        var app = new CliApplicationBuilder()
+            .AddCommandsFromThisAssembly()
+            .UseConsole(FakeConsole)
+            .Build();
 
-            var exitCode = await app.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        var exitCode = await app.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            // Assert
-            exitCode.Should().Be(0);
-        }
+        // Assert
+        exitCode.Should().Be(0);
+    }
 
-        [Fact]
-        public async Task Application_can_be_created_with_a_fully_customized_configuration()
-        {
-            // Act
-            var app = new CliApplicationBuilder()
-                .AddCommand<NoOpCommand>()
-                .AddCommandsFrom(typeof(NoOpCommand).Assembly)
-                .AddCommands(new[] {typeof(NoOpCommand)})
-                .AddCommandsFrom(new[] {typeof(NoOpCommand).Assembly})
-                .AddCommandsFromThisAssembly()
-                .AllowDebugMode()
-                .AllowPreviewMode()
-                .SetTitle("test")
-                .SetExecutableName("test")
-                .SetVersion("test")
-                .SetDescription("test")
-                .UseConsole(FakeConsole)
-                .UseTypeActivator(Activator.CreateInstance!)
-                .Build();
+    [Fact]
+    public async Task Application_can_be_created_with_a_fully_customized_configuration()
+    {
+        // Act
+        var app = new CliApplicationBuilder()
+            .AddCommand<NoOpCommand>()
+            .AddCommandsFrom(typeof(NoOpCommand).Assembly)
+            .AddCommands(new[] {typeof(NoOpCommand)})
+            .AddCommandsFrom(new[] {typeof(NoOpCommand).Assembly})
+            .AddCommandsFromThisAssembly()
+            .AllowDebugMode()
+            .AllowPreviewMode()
+            .SetTitle("test")
+            .SetExecutableName("test")
+            .SetVersion("test")
+            .SetDescription("test")
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(Activator.CreateInstance!)
+            .Build();
 
-            var exitCode = await app.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        var exitCode = await app.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            // Assert
-            exitCode.Should().Be(0);
-        }
+        // Assert
+        exitCode.Should().Be(0);
+    }
 
-        [Fact]
-        public async Task Application_configuration_fails_if_an_invalid_command_is_registered()
-        {
-            // Act
-            var app = new CliApplicationBuilder()
-                .AddCommand(typeof(ApplicationSpecs))
-                .UseConsole(FakeConsole)
-                .Build();
+    [Fact]
+    public async Task Application_configuration_fails_if_an_invalid_command_is_registered()
+    {
+        // Act
+        var app = new CliApplicationBuilder()
+            .AddCommand(typeof(ApplicationSpecs))
+            .UseConsole(FakeConsole)
+            .Build();
 
-            var exitCode = await app.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        var exitCode = await app.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("not a valid command");
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        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
-{
-    public class CancellationSpecs : SpecsBase
-    {
-        public CancellationSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
+namespace CliFx.Tests;
 
-        [Fact]
-        public async Task Command_can_register_to_receive_a_cancellation_signal_from_the_console()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+public class CancellationSpecs : SpecsBase
+{
+    public CancellationSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
+    {
+    }
+
+    [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()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            FakeConsole.RequestCancellation(TimeSpan.FromSeconds(0.2));
+        // Act
+        FakeConsole.RequestCancellation(TimeSpan.FromSeconds(0.2));
 
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdOut.Trim().Should().Be("Cancelled");
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        stdOut.Trim().Should().Be("Cancelled");
     }
 }

CliFx.Tests/CliFx.Tests.csproj

@@ -1,9 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
-    <IsPackable>false</IsPackable>
-    <IsTestProject>true</IsTestProject>
+    <TargetFramework>net6.0</TargetFramework>
     <CollectCoverage>true</CollectCoverage>
     <CoverletOutputFormat>opencover</CoverletOutputFormat>
   </PropertyGroup>
@@ -13,14 +11,15 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="CliWrap" Version="3.3.1" />
-    <PackageReference Include="FluentAssertions" Version="5.10.3" />
+    <PackageReference Include="Basic.Reference.Assemblies" Version="1.2.4" />
+    <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.NET.Test.Sdk" Version="16.9.1" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" />
+    <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]
-        public async Task Real_console_maps_directly_to_system_console()
-        {
-            // Can't verify our own console output, so using an
-            // external process for this test.
+    [Fact]
+    public async Task Real_console_maps_directly_to_system_console()
+    {
+        // Can't verify our own console output, so using an
+        // external process for this test.
 
-            // Arrange
-            var command = "Hello world" | Cli.Wrap("dotnet")
-                .WithArguments(a => a
-                    .Add(Dummy.Program.Location)
-                    .Add("console-test"));
+        // Arrange
+        var command = "Hello world" | Cli.Wrap("dotnet")
+            .WithArguments(a => a
+                .Add(Dummy.Program.Location)
+                .Add("console-test"));
 
-            // Act
-            var result = await command.ExecuteBufferedAsync();
+        // Act
+        var result = await command.ExecuteBufferedAsync();
 
-            // Assert
-            result.StandardOutput.Trim().Should().Be("Hello world");
-            result.StandardError.Trim().Should().Be("Hello world");
-        }
+        // Assert
+        result.StandardOutput.Trim().Should().Be("Hello world");
+        result.StandardError.Trim().Should().Be("Hello world");
+    }
 
-        [Fact]
-        public async Task Fake_console_does_not_leak_to_system_console()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Fake_console_does_not_leak_to_system_console()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {   
@@ -63,43 +66,43 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            // Assert
-            exitCode.Should().Be(0);
+        // Assert
+        exitCode.Should().Be(0);
 
-            Console.OpenStandardInput().Should().NotBe(FakeConsole.Input.BaseStream);
-            Console.OpenStandardOutput().Should().NotBe(FakeConsole.Output.BaseStream);
-            Console.OpenStandardError().Should().NotBe(FakeConsole.Error.BaseStream);
+        Console.OpenStandardInput().Should().NotBeSameAs(FakeConsole.Input.BaseStream);
+        Console.OpenStandardOutput().Should().NotBeSameAs(FakeConsole.Output.BaseStream);
+        Console.OpenStandardError().Should().NotBeSameAs(FakeConsole.Error.BaseStream);
 
-            Console.ForegroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
-            Console.BackgroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
+        Console.ForegroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
+        Console.BackgroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
 
-            // This fails because tests don't spawn a console window
-            //Console.CursorLeft.Should().NotBe(42);
-            //Console.CursorTop.Should().NotBe(24);
+        // This fails because tests don't spawn a console window
+        //Console.CursorLeft.Should().NotBe(42);
+        //Console.CursorTop.Should().NotBe(24);
 
-            FakeConsole.IsInputRedirected.Should().BeTrue();
-            FakeConsole.IsOutputRedirected.Should().BeTrue();
-            FakeConsole.IsErrorRedirected.Should().BeTrue();
-        }
+        FakeConsole.IsInputRedirected.Should().BeTrue();
+        FakeConsole.IsOutputRedirected.Should().BeTrue();
+        FakeConsole.IsErrorRedirected.Should().BeTrue();
+    }
 
-        [Fact]
-        public async Task Fake_console_can_be_used_with_an_in_memory_backing_store()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Fake_console_can_be_used_with_an_in_memory_backing_store()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {   
@@ -114,26 +117,42 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            FakeConsole.WriteInput("Hello world");
+        // Act
+        FakeConsole.WriteInput("Hello world");
 
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdOut = FakeConsole.ReadOutputString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("Hello world");
-            stdErr.Trim().Should().Be("Hello world");
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.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]
-        public async Task Debug_directive_can_be_specified_to_interrupt_execution_until_a_debugger_is_attached()
-        {
-            // Arrange
-            var stdOutBuffer = new StringBuilder();
+            var task = command.ExecuteAsync(cts.Token);
 
-            var command = Cli.Wrap("dotnet")
-                .WithArguments(a => a
-                    .Add(Dummy.Program.Location)
-                    .Add("[debug]")) | stdOutBuffer;
-
-            // Act
-            try
+            // 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)
             {
-                // This has a timeout just in case the execution hangs forever
-                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)
                 {
-                    if (stdOutBuffer.Length > 0)
-                    {
-                        cts.Cancel();
-                        break;
-                    }
-
-                    await Task.Delay(100, cts.Token);
+                    cts.Cancel();
+                    break;
                 }
 
-                await task;
-            }
-            catch (OperationCanceledException)
-            {
-                // It's expected to fail
+                await Task.Delay(100, cts.Token);
             }
 
-            var stdOut = stdOutBuffer.ToString();
-
-            // Assert
-            stdOut.Should().Contain("Attach debugger to");
-
-            TestOutput.WriteLine(stdOut);
+            await task;
+        }
+        catch (OperationCanceledException)
+        {
+            // It's expected to fail
         }
 
-        [Fact]
-        public async Task Preview_directive_can_be_specified_to_print_command_input()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+        var stdOut = stdOutBuffer.ToString();
+
+        // Assert
+        stdOut.Should().Contain("Attach debugger to");
+
+        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()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .AllowPreviewMode()
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .AllowPreviewMode()
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"[preview]", "cmd", "param", "-abc", "--option", "foo"},
-                new Dictionary<string, string>
-                {
-                    ["ENV_QOP"] = "hello",
-                    ["ENV_KIL"] = "world"
-                }
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"[preview]", "cmd", "param", "-abc", "--option", "foo"},
+            new Dictionary<string, string>
+            {
+                ["ENV_QOP"] = "hello",
+                ["ENV_KIL"] = "world"
+            }
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Should().ContainAllInOrder(
-                "cmd", "<param>", "[-a]", "[-b]", "[-c]", "[--option \"foo\"]",
-                "ENV_QOP", "=", "\"hello\"",
-                "ENV_KIL", "=", "\"world\""
-            );
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Should().ContainAllInOrder(
+            "cmd", "<param>", "[-a]", "[-b]", "[-c]", "[--option \"foo\"]",
+            "ENV_QOP", "=", "\"hello\"",
+            "ENV_KIL", "=", "\"world\""
+        );
     }
 }

CliFx.Tests/EnvironmentSpecs.cs

@@ -10,22 +10,22 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
-{
-    public class EnvironmentSpecs : SpecsBase
-    {
-        public EnvironmentSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
+namespace CliFx.Tests;
 
-        [Fact]
-        public async Task Option_can_fall_back_to_an_environment_variable()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+public class EnvironmentSpecs : SpecsBase
+{
+    public EnvironmentSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
+    {
+    }
+
+    [Fact]
+    public async Task Option_can_fall_back_to_an_environment_variable()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -40,34 +40,34 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>
-                {
-                    ["ENV_FOO"] = "bar"
-                }
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>
+            {
+                ["ENV_FOO"] = "bar"
+            }
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("bar");
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().Be("bar");
+    }
 
-        [Fact]
-        public async Task Option_does_not_fall_back_to_an_environment_variable_if_a_value_is_provided_through_arguments()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Option_does_not_fall_back_to_an_environment_variable_if_a_value_is_provided_through_arguments()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -82,34 +82,34 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"--foo", "baz"},
-                new Dictionary<string, string>
-                {
-                    ["ENV_FOO"] = "bar"
-                }
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"--foo", "baz"},
+            new Dictionary<string, string>
+            {
+                ["ENV_FOO"] = "bar"
+            }
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("baz");
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().Be("baz");
+    }
 
-        [Fact]
-        public async Task Option_of_non_scalar_type_can_receive_multiple_values_from_an_environment_variable()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Option_of_non_scalar_type_can_receive_multiple_values_from_an_environment_variable()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -126,37 +126,37 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>
-                {
-                    ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
-                }
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>
+            {
+                ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
+            }
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Should().ConsistOfLines(
-                "bar",
-                "baz"
-            );
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Should().ConsistOfLines(
+            "bar",
+            "baz"
+        );
+    }
 
-        [Fact]
-        public async Task Option_of_scalar_type_always_receives_a_single_value_from_an_environment_variable()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Option_of_scalar_type_always_receives_a_single_value_from_an_environment_variable()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -171,34 +171,34 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>
-                {
-                    ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
-                }
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>
+            {
+                ["ENV_FOO"] = $"bar{Path.PathSeparator}baz"
+            }
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be($"bar{Path.PathSeparator}baz");
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().Be($"bar{Path.PathSeparator}baz");
+    }
 
-        [Fact]
-        public async Task Environment_variables_are_matched_case_sensitively()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Environment_variables_are_matched_case_sensitively()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -213,48 +213,47 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>
-                {
-                    ["ENV_foo"] = "baz",
-                    ["ENV_FOO"] = "bar",
-                    ["env_FOO"] = "qop"
-                }
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>
+            {
+                ["ENV_foo"] = "baz",
+                ["ENV_FOO"] = "bar",
+                ["env_FOO"] = "qop"
+            }
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("bar");
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().Be("bar");
+    }
 
-        [Fact]
-        public async Task Environment_variables_are_extracted_automatically()
-        {
-            // Ensures that the environment variables are properly obtained from
-            // System.Environment when they are not provided explicitly to CliApplication.
+    [Fact]
+    public async Task Environment_variables_are_extracted_automatically()
+    {
+        // Ensures that the environment variables are properly obtained from
+        // System.Environment when they are not provided explicitly to CliApplication.
 
-            // Arrange
-            var command = Cli.Wrap("dotnet")
-                .WithArguments(a => a
-                    .Add(Dummy.Program.Location)
-                    .Add("env-test"))
-                .WithEnvironmentVariables(e => e
-                    .Set("ENV_TARGET", "Mars"));
+        // Arrange
+        var command = Cli.Wrap("dotnet")
+            .WithArguments(a => a
+                .Add(Dummy.Program.Location)
+                .Add("env-test"))
+            .WithEnvironmentVariables(e => e
+                .Set("ENV_TARGET", "Mars"));
 
-            // Act
-            var result = await command.ExecuteBufferedAsync();
+        // Act
+        var result = await command.ExecuteBufferedAsync();
 
-            // Assert
-            result.StandardOutput.Trim().Should().Be("Hello Mars!");
-        }
+        // Assert
+        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
-{
-    public class ErrorReportingSpecs : SpecsBase
-    {
-        public ErrorReportingSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
+namespace CliFx.Tests;
 
-        [Fact]
-        public async Task Command_can_throw_an_exception_which_exits_with_a_stacktrace()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+public class ErrorReportingSpecs : SpecsBase
+{
+    public ErrorReportingSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
+    {
+    }
+
+    [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()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdOut = FakeConsole.ReadOutputString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdOut.Should().BeEmpty();
-            stdErr.Should().ContainAllInOrder(
-                "System.Exception", "Something went wrong",
-                "at", "CliFx."
-            );
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        stdOut.Should().BeEmpty();
+        stdErr.Should().ContainAllInOrder(
+            "System.Exception", "Something went wrong",
+            "at", "CliFx."
+        );
+    }
 
-        [Fact]
-        public async Task Command_can_throw_an_exception_with_an_inner_exception_which_exits_with_a_stacktrace()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Command_can_throw_an_exception_with_an_inner_exception_which_exits_with_a_stacktrace()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -69,37 +69,37 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdOut = FakeConsole.ReadOutputString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdOut.Should().BeEmpty();
-            stdErr.Should().ContainAllInOrder(
-                "System.Exception", "Something went wrong",
-                "System.Exception", "Another exception",
-                "at", "CliFx."
-            );
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        stdOut.Should().BeEmpty();
+        stdErr.Should().ContainAllInOrder(
+            "System.Exception", "Something went wrong",
+            "System.Exception", "Another exception",
+            "at", "CliFx."
+        );
+    }
 
-        [Fact]
-        public async Task Command_can_throw_a_special_exception_which_exits_with_specified_code_and_message()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Command_can_throw_a_special_exception_which_exits_with_specified_code_and_message()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -108,33 +108,33 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdOut = FakeConsole.ReadOutputString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().Be(69);
-            stdOut.Should().BeEmpty();
-            stdErr.Trim().Should().Be("Something went wrong");
-        }
+        // Assert
+        exitCode.Should().Be(69);
+        stdOut.Should().BeEmpty();
+        stdErr.Trim().Should().Be("Something went wrong");
+    }
 
-        [Fact]
-        public async Task Command_can_throw_a_special_exception_without_message_which_exits_with_a_stacktrace()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Command_can_throw_a_special_exception_without_message_which_exits_with_a_stacktrace()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -143,36 +143,36 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdOut = FakeConsole.ReadOutputString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().Be(69);
-            stdOut.Should().BeEmpty();
-            stdErr.Should().ContainAllInOrder(
-                "CliFx.Exceptions.CommandException",
-                "at", "CliFx."
-            );
-        }
+        // Assert
+        exitCode.Should().Be(69);
+        stdOut.Should().BeEmpty();
+        stdErr.Should().ContainAllInOrder(
+            "CliFx.Exceptions.CommandException",
+            "at", "CliFx."
+        );
+    }
 
-        [Fact]
-        public async Task Command_can_throw_a_special_exception_which_prints_help_text_before_exiting()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Command_can_throw_a_special_exception_which_prints_help_text_before_exiting()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -181,25 +181,24 @@ public class Command : ICommand
 }
 ");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .SetDescription("This will be in help text")
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .SetDescription("This will be in help text")
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdOut = FakeConsole.ReadOutputString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().Be(69);
-            stdOut.Should().Contain("This will be in help text");
-            stdErr.Trim().Should().Be("Something went wrong");
-        }
+        // Assert
+        exitCode.Should().Be(69);
+        stdOut.Should().Contain("This will be in help text");
+        stdErr.Trim().Should().Be("Something went wrong");
     }
 }

CliFx.Tests/ParameterBindingSpecs.cs

@@ -6,22 +6,22 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
-{
-    public class ParameterBindingSpecs : SpecsBase
-    {
-        public ParameterBindingSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
+namespace CliFx.Tests;
 
-        [Fact]
-        public async Task Parameter_is_bound_from_an_argument_matching_its_order()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+public class ParameterBindingSpecs : SpecsBase
+{
+    public ParameterBindingSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
+    {
+    }
+
+    [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
 {
@@ -40,34 +40,34 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"one", "two"},
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"one", "two"},
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Should().ConsistOfLines(
-                "Foo = one",
-                "Bar = two"
-            );
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Should().ConsistOfLines(
+            "Foo = one",
+            "Bar = two"
+        );
+    }
 
-        [Fact]
-        public async Task Parameter_of_non_scalar_type_is_bound_from_remaining_non_option_arguments()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Parameter_of_non_scalar_type_is_bound_from_remaining_non_option_arguments()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -95,37 +95,83 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"one", "two", "three", "four", "five", "--boo", "xxx"},
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"one", "two", "three", "four", "five", "--boo", "xxx"},
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Should().ConsistOfLines(
-                "Foo = one",
-                "Bar = two",
-                "Baz = three",
-                "Baz = four",
-                "Baz = five"
-            );
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Should().ConsistOfLines(
+            "Foo = one",
+            "Bar = two",
+            "Baz = three",
+            "Baz = four",
+            "Baz = five"
+        );
+    }
 
-        [Fact]
-        public async Task Parameter_binding_fails_if_one_of_the_parameters_has_not_been_provided()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Parameter_is_not_bound_if_there_are_no_arguments_matching_its_order()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // 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
 {
@@ -138,31 +184,31 @@ public class Command : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"one"},
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"one"},
+            new Dictionary<string, string>()
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Missing parameter(s)");
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        stdErr.Should().Contain("Missing required parameter(s)");
+    }
 
-        [Fact]
-        public async Task Parameter_binding_fails_if_a_parameter_of_non_scalar_type_has_not_been_provided_with_at_least_one_value()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Parameter_binding_fails_if_a_parameter_of_non_scalar_type_has_not_been_provided_with_at_least_one_value()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -175,31 +221,31 @@ public class Command : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"one"},
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"one"},
+            new Dictionary<string, string>()
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Missing parameter(s)");
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        stdErr.Should().Contain("Missing required parameter(s)");
+    }
 
-        [Fact]
-        public async Task Parameter_binding_fails_if_one_of_the_provided_parameters_is_unexpected()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Parameter_binding_fails_if_one_of_the_provided_parameters_is_unexpected()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -212,22 +258,21 @@ public class Command : ICommand
     public ValueTask ExecuteAsync(IConsole console) => default;
 }");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"one", "two", "three"},
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"one", "two", "three"},
+            new Dictionary<string, string>()
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Unexpected parameter(s)");
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        stdErr.Should().Contain("Unexpected parameter(s)");
     }
 }

CliFx.Tests/RoutingSpecs.cs

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

CliFx.Tests/TypeActivationSpecs.cs

@@ -7,22 +7,22 @@ using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
 
-namespace CliFx.Tests
-{
-    public class TypeActivationSpecs : SpecsBase
-    {
-        public TypeActivationSpecs(ITestOutputHelper testOutput)
-            : base(testOutput)
-        {
-        }
+namespace CliFx.Tests;
 
-        [Fact]
-        public async Task Default_type_activator_can_initialize_a_type_if_it_has_a_parameterless_constructor()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+public class TypeActivationSpecs : SpecsBase
+{
+    public TypeActivationSpecs(ITestOutputHelper testOutput)
+        : base(testOutput)
+    {
+    }
+
+    [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()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .UseTypeActivator(new DefaultTypeActivator())
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(new DefaultTypeActivator())
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("foo");
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().Be("foo");
+    }
 
-        [Fact]
-        public async Task Default_type_activator_fails_if_the_type_does_not_have_a_parameterless_constructor()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Default_type_activator_fails_if_the_type_does_not_have_a_parameterless_constructor()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // 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()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .UseTypeActivator(new DefaultTypeActivator())
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(new DefaultTypeActivator())
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Failed to create an instance of type");
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        stdErr.Should().Contain("Failed to create an instance of type");
+    }
 
-        [Fact]
-        public async Task Delegate_type_activator_can_initialize_a_type_using_a_custom_function()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Delegate_type_activator_can_initialize_a_type_using_a_custom_function()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -107,32 +107,32 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .UseTypeActivator(type => Activator.CreateInstance(type, "hello world")!)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(type => Activator.CreateInstance(type, "hello world")!)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdOut = FakeConsole.ReadOutputString();
+        var stdOut = FakeConsole.ReadOutputString();
 
-            // Assert
-            exitCode.Should().Be(0);
-            stdOut.Trim().Should().Be("hello world");
-        }
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().Be("hello world");
+    }
 
-        [Fact]
-        public async Task Delegate_type_activator_fails_if_the_underlying_function_returns_null()
-        {
-            // Arrange
-            var commandType = DynamicCommandBuilder.Compile(
-                // language=cs
-                @"
+    [Fact]
+    public async Task Delegate_type_activator_fails_if_the_underlying_function_returns_null()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
 [Command]
 public class Command : ICommand
 {
@@ -143,23 +143,22 @@ public class Command : ICommand
     }
 }");
 
-            var application = new CliApplicationBuilder()
-                .AddCommand(commandType)
-                .UseConsole(FakeConsole)
-                .UseTypeActivator(_ => null!)
-                .Build();
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(_ => null!)
+            .Build();
 
-            // Act
-            var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
-                new Dictionary<string, string>()
-            );
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
-            var stdErr = FakeConsole.ReadErrorString();
+        var stdErr = FakeConsole.ReadErrorString();
 
-            // Assert
-            exitCode.Should().NotBe(0);
-            stdErr.Should().Contain("Failed to create an instance of type");
-        }
+        // Assert
+        exitCode.Should().NotBe(0);
+        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.
-    //
-    // 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)
     {
-        public static IReadOnlyList<Type> CompileMany(string sourceCode)
+        // Get default system namespaces
+        var defaultSystemNamespaces = new[]
         {
-            // Get default system namespaces
-            var defaultSystemNamespaces = new[]
-            {
-                "System",
-                "System.Collections",
-                "System.Collections.Generic",
-                "System.Linq",
-                "System.Threading.Tasks",
-                "System.Globalization"
-            };
+            "System",
+            "System.Collections",
+            "System.Collections.Generic",
+            "System.Linq",
+            "System.Threading.Tasks",
+            "System.Globalization"
+        };
 
-            // Get default CliFx namespaces
-            var defaultCliFxNamespaces = typeof(ICommand)
-                .Assembly
-                .GetTypes()
-                .Where(t => t.IsPublic)
-                .Select(t => t.Namespace)
-                .Distinct()
-                .ToArray();
+        // 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};")) +
+        // 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))
+                .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;
-
-            // Parse the source code
-            var ast = SyntaxFactory.ParseSyntaxTree(
-                SourceText.From(sourceCodeWithUsings),
-                CSharpParseOptions.Default
+                string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))
             );
-
-            // 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);
-
-            if (commandTypes.Count > 1)
-            {
-                throw new InvalidOperationException(
-                    "There are more than one command definitions in the provide source code."
-                );
-            }
-
-            return commandTypes.Single();
+            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)) && !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(
-            this StringAssertions assertions,
-            IEnumerable<string> lines)
+        var actualLines = assertions.Subject.Split(new[] {'\n', '\r'}, StringSplitOptions.RemoveEmptyEntries);
+        actualLines.Should().Equal(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);
-        }
-
-        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)
+            if (index < 0)
             {
-                var index = assertions.Subject.IndexOf(value, lastIndex, StringComparison.Ordinal);
-
-                if (index < 0)
-                {
-                    Execute.Assertion.FailWith(
-                        $"Expected string '{assertions.Subject}' to contain '{value}' after position {lastIndex}."
-                    );
-                }
-
-                lastIndex = index;
+                Execute.Assertion.FailWith(
+                    $"Expected string '{assertions.Subject}' to contain '{value}' after position {lastIndex}."
+                );
             }
 
-            return new(assertions);
+            lastIndex = index;
         }
 
-        public static AndConstraint<StringAssertions> ContainAllInOrder(
-            this StringAssertions assertions,
-            params string[] values) =>
-            assertions.ContainAllInOrder((IEnumerable<string>) values);
+        return new(assertions);
     }
+
+    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
-{
-    internal static class ConsoleExtensions
-    {
-        public static void DumpToTestOutput(this FakeInMemoryConsole console, ITestOutputHelper testOutputHelper)
-        {
-            testOutputHelper.WriteLine("[*] Captured standard output:");
-            testOutputHelper.WriteLine(console.ReadOutputString());
+namespace CliFx.Tests.Utils.Extensions;
 
-            testOutputHelper.WriteLine("[*] Captured standard error:");
-            testOutputHelper.WriteLine(console.ReadErrorString());
-        }
+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:");
+        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 class NoOpCommand : ICommand
-    {
-        public ValueTask ExecuteAsync(IConsole console) => default;
-    }
+    public ValueTask ExecuteAsync(IConsole console) => default;
 }