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

@@ -1,25 +0,0 @@
-name: CD
-
-on:
-  push:
-    tags:
-      - "*"
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2.3.3
-
-      - name: Install .NET
-        uses: actions/setup-dotnet@v1.7.2
-        with:
-          dotnet-version: 5.0.100
-
-      - name: Pack
-        run: dotnet pack CliFx --configuration Release
-
-      - name: Deploy
-        run: dotnet nuget push CliFx/bin/Release/*.nupkg -s nuget.org -k ${{ secrets.NUGET_TOKEN }}

.github/workflows/CI.yml

@@ -1,28 +0,0 @@
-name: CI
-
-on: [push, pull_request]
-
-jobs:
-  build:
-    runs-on: ${{ matrix.os }}
-
-    strategy:
-      matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest]
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2.3.3
-
-      - name: Install .NET
-        uses: actions/setup-dotnet@v1.7.2
-        with:
-          dotnet-version: 5.0.100
-
-      - name: Build & test
-        run: dotnet test --configuration Release --logger GitHubActions
-
-      - name: Upload coverage
-        uses: codecov/codecov-action@v1.0.5
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }}

.github/workflows/main.yml

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

Changelog.md

@@ -1,3 +1,82 @@
+### 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.
+Please refer to the readme to find updated instructions and usage examples.
+
+- Renamed property `EnvironmentVariableName` to `EnvironmentVariable` on `CommandOption` attribute.
+- Removed most of schema validation checks that used to take place during application startup. Going forward, CliFx will be relying solely on its built-in set of Roslyn analyzers to catch common errors in command configuration.
+- Removed `ProgressTicker` utility. The recommended migration path is to use the [Spectre.Console](https://github.com/spectresystems/spectre.console) library which provides a wide array of console widgets and components. See [this wiki page](https://github.com/Tyrrrz/CliFx/wiki/Integrating-with-Spectre.Console) to learn how to integrate Spectre.Console with CliFx.
+- Removed `MemoryStreamWriter` utility as it's no longer used within CliFx.
+- Improved wording in all error messages.
+- Renamed some methods on `CliApplicationBuilder`:
+  - `UseTitle()` renamed to `SetTitle()`
+  - `UseExecutableName()` renamed to `SetExecutableName()`
+  - `UseVersionText()` renamed to `SetVersion()`
+  - `UseDescription()` renamed to `SetDescription()`
+- Changed the behavior of autogenerated help text:
+  - Changed the color scheme to a more neutral set of tones
+  - Assigned separate colors to parameters and options to make them visually stand out
+  - Usage section no longer lists usage formats of all descendant commands
+  - Command section now also lists available subcommands for each of the current command's subcommands
+- Changed the behavior of `[preview]` directive. Running the application with this directive will now also print all resolved environment variables, in addition to parsed command line arguments.
+- Reworked `IArgumentValueConverter`/`ArgumentValueConverter` into `BindingConverter`. Method `ConvertFrom(...)` has been renamed to `Convert(...)`.
+- Reworked `ArgumentValueValidator` into `BindingValidator`. This class exposes an abstract `Validate(...)` method that returns a nullable `BindingValidationError`. This class also provides utility methods `Ok()` and `Error(...)` to help create corresponding validation results.
+- Changed the type of `IConsole.Output` and `IConsole.Error` from `StreamWriter` to `ConsoleWriter`. This type derives from `StreamWriter` and additionally exposes a `Console` property that refers to the console instance that owns the stream. This change enables you to author extension methods scoped specifically to console output and error streams.
+- Changed the type of `IConsole.Input` from `StreamReader` to `ConsoleReader`. This type derives from `StreamReader` and additionally exposes a `Console` property that refers to the console instance that owns the stream. This change enables you to author extension methods scoped specifically to the console input stream.
+- Changed methods `IConsole.WithForegroundColor(...)`, `IConsole.WithBackgroundColor(...)`, and `IConsole.WithColors(...)` to return `IDisposable`, replacing the delegate parameter they previously had. You can wrap the returned `IDisposable` in a using statement to ensure that the console colors get reset back to their original values once the execution reaches the end of the block.
+- Renamed `IConsole.GetCancellationToken()` to `IConsole.RegisterCancellationHandler()`.
+- Reworked `VirtualConsole` into `FakeConsole`. This class no longer takes `CancellationToken` as a constructor parameter, but instead encapsulates its own instance of `CancellationTokenSource` that can be triggered using the provided `RequestCancellation()` method.
+- Removed `VirtualConsole.CreateBuffered()` and replaced it with the `FakeInMemoryConsole` class. This class derives from `FakeConsole` and uses in-memory standard input, output, and error streams. It also provides methods to easily read the data written to the streams.
+- Moved some types to different namespaces:
+  - `IConsole`/`FakeConsole`/`FakeInMemoryConsole` moved from `CliFx` to `CliFx.Infrastructure`
+  - `ITypeActivator`/`DefaultTypeActivator`/`DelegateTypeActivator` moved from `CliFx` to `CliFx.Infrastructure`
+  - `BindingValidator`/`BindingConverter` moved from `CliFx` to `CliFx.Extensibility`
+
 ### v1.6 (06-Dec-2020)
 
 - Added support for custom value validators. You can now create a type that inherits from `CliFx.ArgumentValueValidator<T>` to implement reusable validation logic for command arguments. To use a validator, include it in the `Validators` property on the `CommandOption` or `CommandParameter` attribute. (Thanks [@Oleksandr Shustov](https://github.com/AlexandrShustov))
@@ -17,7 +96,7 @@
 
 ### v1.3.2 (31-Jul-2020)
 
-- Fixed an issue where a command was incorrectly allowed to execute when the user did not specify any value for a non-scalar parameter. Since they are always required, a parameter needs to be bound to (at least) one value. (Thanks [@Daniel Hix](https://github.com/ADustyOldMuffin))
+- Fixed an issue where a command was incorrectly allowed to execute when the user did not specify any value for a non-scalar parameter. Since they are always required, a parameter needs to be bound to at least one value. (Thanks [@Daniel Hix](https://github.com/ADustyOldMuffin))
 - Fixed an issue where `CliApplication.RunAsync(...)` threw `ArgumentException` if there were two environment variables, whose names differed only in case. Environment variable names are now treated case-sensitively. (Thanks [@Ron Myers](https://github.com/ron-myers))
 
 ### v1.3.1 (19-Jul-2020)

CliFx.Analyzers.Tests/AnalyzerTestCase.cs

@@ -1,43 +0,0 @@
-using System.Collections.Generic;
-using System.Linq;
-using Microsoft.CodeAnalysis;
-
-namespace CliFx.Analyzers.Tests
-{
-    public class AnalyzerTestCase
-    {
-        public string Name { get; }
-
-        public IReadOnlyList<DiagnosticDescriptor> TestedDiagnostics { get; }
-
-        public IReadOnlyList<string> SourceCodes { get; }
-
-        public AnalyzerTestCase(
-            string name,
-            IReadOnlyList<DiagnosticDescriptor> testedDiagnostics,
-            IReadOnlyList<string> sourceCodes)
-        {
-            Name = name;
-            TestedDiagnostics = testedDiagnostics;
-            SourceCodes = sourceCodes;
-        }
-
-        public AnalyzerTestCase(
-            string name,
-            IReadOnlyList<DiagnosticDescriptor> testedDiagnostics,
-            string sourceCode)
-            : this(name, testedDiagnostics, new[] {sourceCode})
-        {
-        }
-
-        public AnalyzerTestCase(
-            string name,
-            DiagnosticDescriptor testedDiagnostic,
-            string sourceCode)
-            : this(name, new[] {testedDiagnostic}, sourceCode)
-        {
-        }
-
-        public override string ToString() => $"{Name} [{string.Join(", ", TestedDiagnostics.Select(d => d.Id))}]";
-    }
-}

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

@@ -1,23 +1,24 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
-    <IsPackable>false</IsPackable>
-    <IsTestProject>true</IsTestProject>
+    <TargetFramework>net6.0</TargetFramework>
     <CollectCoverage>true</CollectCoverage>
     <CoverletOutputFormat>opencover</CoverletOutputFormat>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Gu.Roslyn.Asserts" Version="3.3.1" />
-    <PackageReference Include="GitHubActionsTestLogger" Version="1.1.2" />
-    <PackageReference Include="FluentAssertions" Version="5.10.3" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.7.1" />
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="3.4.0" />
-    <PackageReference Include="xunit" Version="2.4.0" />
+    <Content Include="xunit.runner.json" CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Basic.Reference.Assemblies" Version="1.2.4" />
+    <PackageReference Include="GitHubActionsTestLogger" Version="1.2.0" />
+    <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="2.9.0" PrivateAssets="all" />
+    <PackageReference Include="coverlet.msbuild" Version="3.1.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Analyzers.Tests/CommandMustBeAnnotatedAnalyzerSpecs.cs

@@ -0,0 +1,71 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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);
+    }
+
+    [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);
+    }
+
+    [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);
+    }
+
+    [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);
+    }
+}

CliFx.Analyzers.Tests/CommandMustImplementInterfaceAnalyzerSpecs.cs

@@ -0,0 +1,57 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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);
+    }
+
+    [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);
+    }
+
+    [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);
+    }
+}

CliFx.Analyzers.Tests/CommandSchemaAnalyzerTests.cs

@@ -1,719 +0,0 @@
-using System.Collections.Generic;
-using CliFx.Analyzers.Tests.Internal;
-using Microsoft.CodeAnalysis.Diagnostics;
-using Xunit;
-
-namespace CliFx.Analyzers.Tests
-{
-    public class CommandSchemaAnalyzerTests
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new CommandSchemaAnalyzer();
-
-        public static IEnumerable<object[]> GetValidCases()
-        {
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Non-command type",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-public class Foo
-{
-    public int Bar { get; set; } = 5;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Command implements interface and has attribute",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Command doesn't have an attribute but is an abstract type",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-public abstract class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameters with unique order",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(13)]
-    public string ParamA { get; set; }
-    
-    [CommandParameter(15)]
-    public string ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameters with unique names",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(13, Name = ""foo"")]
-    public string ParamA { get; set; }
-    
-    [CommandParameter(15, Name = ""bar"")]
-    public string ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Single non-scalar parameter",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(1)]
-    public string ParamA { get; set; }
-    
-    [CommandParameter(2)]
-    public HashSet<string> ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Non-scalar parameter is last in order",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(1)]
-    public string ParamA { get; set; }
-    
-    [CommandParameter(2)]
-    public IReadOnlyList<string> ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameter with valid converter",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-public class MyConverter : ArgumentValueConverter<string>
-{
-    public string ConvertFrom(string value) => value;
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Converter = typeof(MyConverter))]
-    public string Param { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameter with valid validator",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-public class MyValidator : ArgumentValueValidator<string>
-{
-    public ValidationResult Validate(string value) => ValidationResult.Ok();
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
-    public string Param { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with a proper name",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Option { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with a proper name and short name",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"", 'f')]
-    public string Option { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Options with unique names",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string OptionA { get; set; }
-    
-    [CommandOption(""bar"")]
-    public string OptionB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Options with unique short names",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('f')]
-    public string OptionA { get; set; }
-    
-    [CommandOption('x')]
-    public string OptionB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Options with unique environment variable names",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('a', EnvironmentVariableName = ""env_var_a"")]
-    public string OptionA { get; set; }
-    
-    [CommandOption('b', EnvironmentVariableName = ""env_var_b"")]
-    public string OptionB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with valid converter",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-public class MyConverter : ArgumentValueConverter<string>
-{
-    public string ConvertFrom(string value) => value;
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('o', Converter = typeof(MyConverter))]
-    public string Option { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with valid validator",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-public class MyValidator : ArgumentValueValidator<string>
-{
-    public ValidationResult Validate(string value) => ValidationResult.Ok();
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('o', Validators = new[] {typeof(MyValidator)})]
-    public string Option { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-        }
-
-        public static IEnumerable<object[]> GetInvalidCases()
-        {
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Command is missing the attribute",
-                    DiagnosticDescriptors.CliFx0002,
-
-                    // language=cs
-                    @"
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Command doesn't implement the interface",
-                    DiagnosticDescriptors.CliFx0001,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameters with duplicate order",
-                    DiagnosticDescriptors.CliFx0021,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(13)]
-    public string ParamA { get; set; }
-    
-    [CommandParameter(13)]
-    public string ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameters with duplicate names",
-                    DiagnosticDescriptors.CliFx0022,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(13, Name = ""foo"")]
-    public string ParamA { get; set; }
-    
-    [CommandParameter(15, Name = ""foo"")]
-    public string ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Multiple non-scalar parameters",
-                    DiagnosticDescriptors.CliFx0023,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(1)]
-    public IReadOnlyList<string> ParamA { get; set; }
-    
-    [CommandParameter(2)]
-    public HashSet<string> ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Non-last non-scalar parameter",
-                    DiagnosticDescriptors.CliFx0024,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(1)]
-    public IReadOnlyList<string> ParamA { get; set; }
-    
-    [CommandParameter(2)]
-    public string ParamB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameter with invalid converter",
-                    DiagnosticDescriptors.CliFx0025,
-
-                    // language=cs
-                    @"
-public class MyConverter
-{
-    public object ConvertFrom(string value) => value;
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Converter = typeof(MyConverter))]
-    public string Param { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Parameter with invalid validator",
-                    DiagnosticDescriptors.CliFx0026,
-
-                    // language=cs
-                    @"
-public class MyValidator
-{
-    public ValidationResult Validate(string value) => ValidationResult.Ok();
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
-    public string Param { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with an empty name",
-                    DiagnosticDescriptors.CliFx0041,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption("""")]
-    public string Option { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with a name which is too short",
-                    DiagnosticDescriptors.CliFx0042,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""a"")]
-    public string Option { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Options with duplicate names",
-                    DiagnosticDescriptors.CliFx0043,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string OptionA { get; set; }
-    
-    [CommandOption(""foo"")]
-    public string OptionB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Options with duplicate short names",
-                    DiagnosticDescriptors.CliFx0044,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('f')]
-    public string OptionA { get; set; }
-    
-    [CommandOption('f')]
-    public string OptionB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Options with duplicate environment variable names",
-                    DiagnosticDescriptors.CliFx0045,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('a', EnvironmentVariableName = ""env_var"")]
-    public string OptionA { get; set; }
-    
-    [CommandOption('b', EnvironmentVariableName = ""env_var"")]
-    public string OptionB { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with invalid converter",
-                    DiagnosticDescriptors.CliFx0046,
-
-                    // language=cs
-                    @"
-public class MyConverter
-{
-    public object ConvertFrom(string value) => value;
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('o', Converter = typeof(MyConverter))]
-    public string Option { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with invalid validator",
-                    DiagnosticDescriptors.CliFx0047,
-
-                    // language=cs
-                    @"
-public class MyValidator
-{
-    public ValidationResult Validate(string value) => ValidationResult.Ok();
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('o', Validators = new[] {typeof(MyValidator)})]
-    public string Option { get; set; }
-    
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with a name that doesn't start with a letter character",
-                    DiagnosticDescriptors.CliFx0048,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""0foo"")]
-    public string Option { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Option with a short name that isn't a letter character",
-                    DiagnosticDescriptors.CliFx0049,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('0')]
-    public string Option { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-        }
-
-        [Theory]
-        [MemberData(nameof(GetValidCases))]
-        public void Valid(AnalyzerTestCase testCase) =>
-            Analyzer.Should().NotProduceDiagnostics(testCase);
-
-        [Theory]
-        [MemberData(nameof(GetInvalidCases))]
-        public void Invalid(AnalyzerTestCase testCase) =>
-            Analyzer.Should().ProduceDiagnostics(testCase);
-    }
-}

CliFx.Analyzers.Tests/ConsoleUsageAnalyzerTests.cs

@@ -1,144 +0,0 @@
-using System.Collections.Generic;
-using CliFx.Analyzers.Tests.Internal;
-using Microsoft.CodeAnalysis.Diagnostics;
-using Xunit;
-
-namespace CliFx.Analyzers.Tests
-{
-    public class ConsoleUsageAnalyzerTests
-    {
-        private static DiagnosticAnalyzer Analyzer { get; } = new ConsoleUsageAnalyzer();
-
-        public static IEnumerable<object[]> GetValidCases()
-        {
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Using console abstraction",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""Hello world"");
-        return default;
-    }
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Console abstraction is not available in scope",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    public void SomeOtherMethod() => Console.WriteLine(""Test"");
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-        }
-
-        public static IEnumerable<object[]> GetInvalidCases()
-        {
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Not using available console abstraction in the ExecuteAsync method",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        Console.WriteLine(""Hello world"");
-        return default;
-    }
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Not using available console abstraction in the ExecuteAsync method when writing stderr",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        Console.Error.WriteLine(""Hello world"");
-        return default;
-    }
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Not using available console abstraction while referencing System.Console by full name",
-                    Analyzer.SupportedDiagnostics,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        System.Console.Error.WriteLine(""Hello world"");
-        return default;
-    }
-}"
-                )
-            };
-
-            yield return new object[]
-            {
-                new AnalyzerTestCase(
-                    "Not using available console abstraction in another method",
-                    DiagnosticDescriptors.CliFx0100,
-
-                    // language=cs
-                    @"
-[Command]
-public class MyCommand : ICommand
-{
-    public void SomeOtherMethod(IConsole console) => Console.WriteLine(""Test"");
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}"
-                )
-            };
-        }
-
-        [Theory]
-        [MemberData(nameof(GetValidCases))]
-        public void Valid(AnalyzerTestCase testCase) =>
-            Analyzer.Should().NotProduceDiagnostics(testCase);
-
-        [Theory]
-        [MemberData(nameof(GetInvalidCases))]
-        public void Invalid(AnalyzerTestCase testCase) =>
-            Analyzer.Should().ProduceDiagnostics(testCase);
-    }
-}

CliFx.Analyzers.Tests/GeneralSpecs.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Linq;
+using FluentAssertions;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+public class GeneralSpecs
+{
+    [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();
+
+        // Act
+        var diagnosticIds = analyzers
+            .SelectMany(a => a.SupportedDiagnostics.Select(d => d.Id))
+            .ToArray();
+
+        // Assert
+        diagnosticIds.Should().OnlyHaveUniqueItems();
+    }
+}

CliFx.Analyzers.Tests/Internal/AnalyzerAssertions.cs

@@ -1,107 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using FluentAssertions.Execution;
-using FluentAssertions.Primitives;
-using Gu.Roslyn.Asserts;
-using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.CSharp;
-using Microsoft.CodeAnalysis.Diagnostics;
-
-namespace CliFx.Analyzers.Tests.Internal
-{
-    internal partial class AnalyzerAssertions : ReferenceTypeAssertions<DiagnosticAnalyzer, AnalyzerAssertions>
-    {
-        protected override string Identifier { get; } = "analyzer";
-
-        public AnalyzerAssertions(DiagnosticAnalyzer analyzer)
-            : base(analyzer)
-        {
-        }
-
-        public void ProduceDiagnostics(
-            IReadOnlyList<DiagnosticDescriptor> diagnostics,
-            IReadOnlyList<string> sourceCodes)
-        {
-            var producedDiagnostics = GetProducedDiagnostics(Subject, sourceCodes);
-
-            var expectedIds = diagnostics.Select(d => d.Id).Distinct().OrderBy(d => d).ToArray();
-            var producedIds = producedDiagnostics.Select(d => d.Id).Distinct().OrderBy(d => d).ToArray();
-
-            var result = expectedIds.Intersect(producedIds).Count() == expectedIds.Length;
-
-            Execute.Assertion.ForCondition(result).FailWith($@"
-Expected and produced diagnostics do not match.
-
-Expected: {string.Join(", ", expectedIds)}
-Produced: {(producedIds.Any() ? string.Join(", ", producedIds) : "<none>")}
-".Trim());
-        }
-
-        public void ProduceDiagnostics(AnalyzerTestCase testCase) =>
-            ProduceDiagnostics(testCase.TestedDiagnostics, testCase.SourceCodes);
-
-        public void NotProduceDiagnostics(
-            IReadOnlyList<DiagnosticDescriptor> diagnostics,
-            IReadOnlyList<string> sourceCodes)
-        {
-            var producedDiagnostics = GetProducedDiagnostics(Subject, sourceCodes);
-
-            var expectedIds = diagnostics.Select(d => d.Id).Distinct().OrderBy(d => d).ToArray();
-            var producedIds = producedDiagnostics.Select(d => d.Id).Distinct().OrderBy(d => d).ToArray();
-
-            var result = !expectedIds.Intersect(producedIds).Any();
-
-            Execute.Assertion.ForCondition(result).FailWith($@"
-Expected no produced diagnostics.
-
-Produced: {string.Join(", ", producedIds)}
-".Trim());
-        }
-
-        public void NotProduceDiagnostics(AnalyzerTestCase testCase) =>
-            NotProduceDiagnostics(testCase.TestedDiagnostics, testCase.SourceCodes);
-    }
-
-    internal partial class AnalyzerAssertions
-    {
-        private static IReadOnlyList<MetadataReference> DefaultMetadataReferences { get; } =
-            MetadataReferences.Transitive(typeof(CliApplication).Assembly).ToArray();
-
-        private static string WrapCodeWithUsingDirectives(string code)
-        {
-            var usingDirectives = new[]
-            {
-                "using System;",
-                "using System.Collections.Generic;",
-                "using System.Threading.Tasks;",
-                "using CliFx;",
-                "using CliFx.Attributes;",
-                "using CliFx.Exceptions;",
-                "using CliFx.Utilities;"
-            };
-
-            return
-                string.Join(Environment.NewLine, usingDirectives) +
-                Environment.NewLine +
-                code;
-        }
-
-        private static IReadOnlyList<Diagnostic> GetProducedDiagnostics(
-            DiagnosticAnalyzer analyzer,
-            IReadOnlyList<string> sourceCodes)
-        {
-            var compilationOptions = new CSharpCompilationOptions(OutputKind.ConsoleApplication);
-            var wrappedSourceCodes = sourceCodes.Select(WrapCodeWithUsingDirectives).ToArray();
-
-            return Analyze.GetDiagnostics(analyzer, wrappedSourceCodes, compilationOptions, DefaultMetadataReferences)
-                .SelectMany(d => d)
-                .ToArray();
-        }
-    }
-
-    internal static class AnalyzerAssertionsExtensions
-    {
-        public static AnalyzerAssertions Should(this DiagnosticAnalyzer analyzer) => new AnalyzerAssertions(analyzer);
-    }
-}

CliFx.Analyzers.Tests/OptionMustBeInsideCommandAnalyzerSpecs.cs

@@ -0,0 +1,79 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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);
+    }
+
+    [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
+{
+    [CommandOption(""foo"")]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+public abstract class MyCommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { get; set; }
+}";
+
+        // 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 = @"
+[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/OptionMustHaveNameOrShortNameAnalyzerSpecs.cs

@@ -0,0 +1,85 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandOption(null)]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption('f')]
+    public string Foo { 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_an_option()
+    {
+        // 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/OptionMustHaveUniqueNameAnalyzerSpecs.cs

@@ -0,0 +1,91 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandOption(""foo"")]
+    public string Foo { get; set; }
+
+    [CommandOption(""foo"")]
+    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_an_option_has_a_unique_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { get; set; }
+
+    [CommandOption(""bar"")]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption('f')]
+    public string Foo { 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_an_option()
+    {
+        // 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/OptionMustHaveUniqueShortNameAnalyzerSpecs.cs

@@ -0,0 +1,113 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandOption('f')]
+    public string Foo { get; set; }
+
+    [CommandOption('f')]
+    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_an_option_has_a_unique_short_name()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption('f')]
+    public string Foo { get; set; }
+
+    [CommandOption('b')]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption('f')]
+    public string Foo { get; set; }
+
+    [CommandOption('F')]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { 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_an_option()
+    {
+        // 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/OptionMustHaveValidConverterAnalyzerSpecs.cs

@@ -0,0 +1,95 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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;
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"", Converter = typeof(MyConverter))]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+public class MyConverter : BindingConverter<string>
+{
+    public override string Convert(string rawValue) => rawValue;
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"", Converter = typeof(MyConverter))]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { 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_an_option()
+    {
+        // 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/OptionMustHaveValidNameAnalyzerSpecs.cs

@@ -0,0 +1,104 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandOption(""f"")]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""1foo"")]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption('f')]
+    public string Foo { 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_an_option()
+    {
+        // 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/OptionMustHaveValidShortNameAnalyzerSpecs.cs

@@ -0,0 +1,85 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandOption('1')]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption('f')]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { 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_an_option()
+    {
+        // 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/OptionMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -0,0 +1,95 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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) {}
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"", Validators = new[] {typeof(MyValidator)})]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+public class MyValidator : BindingValidator<string>
+{
+    public override BindingValidationError Validate(string value) => Ok();
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"", Validators = new[] {typeof(MyValidator)})]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandOption(""foo"")]
+    public string Foo { 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_an_option()
+    {
+        // 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/ParameterMustBeInsideCommandAnalyzerSpecs.cs

@@ -0,0 +1,79 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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);
+    }
+
+    [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
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+public abstract class MyCommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+}";
+
+        // 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/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

@@ -0,0 +1,94 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandParameter(0)]
+    public string[] Foo { get; set; }
+
+    [CommandParameter(1)]
+    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_scalar_parameter_is_the_last_in_order()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1)]
+    public string[] Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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/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

@@ -0,0 +1,94 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandParameter(0)]
+    public string[] Foo { get; set; }
+
+    [CommandParameter(1)]
+    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_scalar_parameter_is_defined()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1)]
+    public string[] Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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/ParameterMustHaveUniqueNameAnalyzerSpecs.cs

@@ -0,0 +1,72 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandParameter(0, Name = ""foo"")]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, Name = ""foo"")]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Name = ""foo"")]
+    public string Foo { get; set; }
+
+    [CommandParameter(1, Name = ""bar"")]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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/ParameterMustHaveUniqueOrderAnalyzerSpecs.cs

@@ -0,0 +1,72 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(0)]
+    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_parameter_has_unique_order()
+    {
+        // Arrange
+        // language=cs
+        const string code = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { get; set; }
+
+    [CommandParameter(1)]
+    public string Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // Act & assert
+        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/ParameterMustHaveValidConverterAnalyzerSpecs.cs

@@ -0,0 +1,95 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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;
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Converter = typeof(MyConverter))]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+public class MyConverter : BindingConverter<string>
+{
+    public override string Convert(string rawValue) => rawValue;
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Converter = typeof(MyConverter))]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { 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/ParameterMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -0,0 +1,95 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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) {}
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+public class MyValidator : BindingValidator<string>
+{
+    public override BindingValidationError Validate(string value) => Ok();
+}
+
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
+    public string Foo { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    [CommandParameter(0)]
+    public string Foo { 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/SystemConsoleShouldBeAvoidedAnalyzerSpecs.cs

@@ -0,0 +1,126 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+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
+{
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        Console.WriteLine(""Hello world"");
+        return default;
+    }
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        Console.ForegroundColor = ConsoleColor.Black;
+        return default;
+    }
+}";
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        Console.Error.WriteLine(""Hello world"");
+        return default;
+    }
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        console.Output.WriteLine(""Hello world"");
+        return default;
+    }
+}";
+
+        // 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 = @"
+[Command]
+public class MyCommand : ICommand
+{
+    public void SomeOtherMethod() => Console.WriteLine(""Test"");
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}";
+
+        // 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

@@ -0,0 +1,167 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using Basic.Reference.Assemblies;
+using FluentAssertions.Execution;
+using FluentAssertions.Primitives;
+using Microsoft.CodeAnalysis;
+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";
+
+    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()))
+            );
+        }
+
+        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(() =>
+        {
+            var buffer = new StringBuilder();
+
+            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());
+        });
+    }
+}
+
+internal static class AnalyzerAssertionsExtensions
+{
+    public static AnalyzerAssertions Should(this DiagnosticAnalyzer analyzer) => new(analyzer);
+}

CliFx.Analyzers.Tests/xunit.runner.json

@@ -0,0 +1,5 @@
+{
+  "$schema": "https://xunit.net/schema/current/xunit.runner.schema.json",
+  "methodDisplayOptions": "all",
+  "methodDisplay": "method"
+}

CliFx.Analyzers/AnalyzerBase.cs

@@ -0,0 +1,39 @@
+using System.Collections.Immutable;
+using CliFx.Analyzers.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace CliFx.Analyzers;
+
+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)
+    {
+        SupportedDiagnostic = new DiagnosticDescriptor(
+            "CliFx_" + GetType().Name.TrimEnd("Analyzer"),
+            diagnosticTitle,
+            diagnosticMessage,
+            "CliFx",
+            diagnosticSeverity,
+            true
+        );
+
+        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);
+    }
+}

CliFx.Analyzers/CliFx.Analyzers.csproj

@@ -1,13 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <Nullable>annotations</Nullable>
+    <NoWarn>$(NoWarn);RS1025;RS1026</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="3.4.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" PrivateAssets="all" />
   </ItemGroup>
 
 </Project>

CliFx.Analyzers/CommandMustBeAnnotatedAnalyzer.cs

@@ -0,0 +1,53 @@
+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 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.")
+    {
+    }
+
+    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);
+    }
+}

CliFx.Analyzers/CommandMustImplementInterfaceAnalyzer.cs

@@ -0,0 +1,47 @@
+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 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.")
+    {
+    }
+
+    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);
+    }
+}

CliFx.Analyzers/CommandSchemaAnalyzer.cs

@@ -1,423 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Linq;
-using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.Diagnostics;
-
-namespace CliFx.Analyzers
-{
-    // TODO: split into multiple analyzers
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
-    public class CommandSchemaAnalyzer : DiagnosticAnalyzer
-    {
-        public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(
-            DiagnosticDescriptors.CliFx0001,
-            DiagnosticDescriptors.CliFx0002,
-            DiagnosticDescriptors.CliFx0021,
-            DiagnosticDescriptors.CliFx0022,
-            DiagnosticDescriptors.CliFx0023,
-            DiagnosticDescriptors.CliFx0024,
-            DiagnosticDescriptors.CliFx0025,
-            DiagnosticDescriptors.CliFx0026,
-            DiagnosticDescriptors.CliFx0041,
-            DiagnosticDescriptors.CliFx0042,
-            DiagnosticDescriptors.CliFx0043,
-            DiagnosticDescriptors.CliFx0044,
-            DiagnosticDescriptors.CliFx0045,
-            DiagnosticDescriptors.CliFx0046,
-            DiagnosticDescriptors.CliFx0047,
-            DiagnosticDescriptors.CliFx0048,
-            DiagnosticDescriptors.CliFx0049
-        );
-
-        private static bool IsScalarType(ITypeSymbol typeSymbol) =>
-            KnownSymbols.IsSystemString(typeSymbol) ||
-            !typeSymbol.AllInterfaces.Select(i => i.ConstructedFrom)
-                .Any(KnownSymbols.IsSystemCollectionsGenericIEnumerable);
-
-        private static void CheckCommandParameterProperties(
-            SymbolAnalysisContext context,
-            IReadOnlyList<IPropertySymbol> properties)
-        {
-            var parameters = properties
-                .Select(p =>
-                {
-                    var attribute = p
-                        .GetAttributes()
-                        .First(a => KnownSymbols.IsCommandParameterAttribute(a.AttributeClass));
-
-                    var order = attribute
-                        .ConstructorArguments
-                        .Select(a => a.Value)
-                        .FirstOrDefault() as int?;
-
-                    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
-                    {
-                        Property = p,
-                        Order = order,
-                        Name = name,
-                        Converter = converter,
-                        Validators = validators
-                    };
-                })
-                .ToArray();
-
-            // Duplicate order
-            var duplicateOrderParameters = parameters
-                .Where(p => p.Order != null)
-                .GroupBy(p => p.Order)
-                .Where(g => g.Count() > 1)
-                .SelectMany(g => g.AsEnumerable())
-                .ToArray();
-
-            foreach (var parameter in duplicateOrderParameters)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0021, parameter.Property.Locations.First()
-                ));
-            }
-
-            // Duplicate name
-            var duplicateNameParameters = parameters
-                .Where(p => !string.IsNullOrWhiteSpace(p.Name))
-                .GroupBy(p => p.Name, StringComparer.OrdinalIgnoreCase)
-                .Where(g => g.Count() > 1)
-                .SelectMany(g => g.AsEnumerable())
-                .ToArray();
-
-            foreach (var parameter in duplicateNameParameters)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0022, parameter.Property.Locations.First()
-                ));
-            }
-
-            // Multiple non-scalar
-            var nonScalarParameters = parameters
-                .Where(p => !IsScalarType(p.Property.Type))
-                .ToArray();
-
-            if (nonScalarParameters.Length > 1)
-            {
-                foreach (var parameter in nonScalarParameters)
-                {
-                    context.ReportDiagnostic(Diagnostic.Create(
-                        DiagnosticDescriptors.CliFx0023, parameter.Property.Locations.First()
-                    ));
-                }
-            }
-
-            // Non-last non-scalar
-            var nonLastNonScalarParameter = parameters
-                .OrderByDescending(a => a.Order)
-                .Skip(1)
-                .LastOrDefault(p => !IsScalarType(p.Property.Type));
-
-            if (nonLastNonScalarParameter != null)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0024, nonLastNonScalarParameter.Property.Locations.First()
-                ));
-            }
-
-            // Invalid converter
-            var invalidConverterParameters = parameters
-                .Where(p =>
-                    p.Converter != null &&
-                    !p.Converter.AllInterfaces.Any(KnownSymbols.IsArgumentValueConverterInterface))
-                .ToArray();
-
-            foreach (var parameter in invalidConverterParameters)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0025, parameter.Property.Locations.First()
-                ));
-            }
-
-            // Invalid validators
-            var invalidValidatorsParameters = parameters
-                .Where(p => !p.Validators.All(v => v.AllInterfaces.Any(KnownSymbols.IsArgumentValueValidatorInterface)))
-                .ToArray();
-
-            foreach (var parameter in invalidValidatorsParameters)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0026, parameter.Property.Locations.First()
-                ));
-            }
-        }
-
-        private static void CheckCommandOptionProperties(
-            SymbolAnalysisContext context,
-            IReadOnlyList<IPropertySymbol> properties)
-        {
-            var options = properties
-                .Select(p =>
-                {
-                    var attribute = p
-                        .GetAttributes()
-                        .First(a => KnownSymbols.IsCommandOptionAttribute(a.AttributeClass));
-
-                    var name = attribute
-                        .ConstructorArguments
-                        .Where(a => KnownSymbols.IsSystemString(a.Type))
-                        .Select(a => a.Value)
-                        .FirstOrDefault() as string;
-
-                    var shortName = attribute
-                        .ConstructorArguments
-                        .Where(a => KnownSymbols.IsSystemChar(a.Type))
-                        .Select(a => a.Value)
-                        .FirstOrDefault() as char?;
-
-                    var envVarName = attribute
-                        .NamedArguments
-                        .Where(a => a.Key == "EnvironmentVariableName")
-                        .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
-                    {
-                        Property = p,
-                        Name = name,
-                        ShortName = shortName,
-                        EnvironmentVariableName = envVarName,
-                        Converter = converter,
-                        Validators = validators
-                    };
-                })
-                .ToArray();
-
-            // No name
-            var noNameOptions = options
-                .Where(o => string.IsNullOrWhiteSpace(o.Name) && o.ShortName == null)
-                .ToArray();
-
-            foreach (var option in noNameOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0041, option.Property.Locations.First()
-                ));
-            }
-
-            // Too short name
-            var invalidNameLengthOptions = options
-                .Where(o => !string.IsNullOrWhiteSpace(o.Name) && o.Name.Length <= 1)
-                .ToArray();
-
-            foreach (var option in invalidNameLengthOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0042, option.Property.Locations.First()
-                ));
-            }
-
-            // Duplicate name
-            var duplicateNameOptions = options
-                .Where(p => !string.IsNullOrWhiteSpace(p.Name))
-                .GroupBy(p => p.Name, StringComparer.OrdinalIgnoreCase)
-                .Where(g => g.Count() > 1)
-                .SelectMany(g => g.AsEnumerable())
-                .ToArray();
-
-            foreach (var option in duplicateNameOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0043, option.Property.Locations.First()
-                ));
-            }
-
-            // Duplicate name
-            var duplicateShortNameOptions = options
-                .Where(p => p.ShortName != null)
-                .GroupBy(p => p.ShortName)
-                .Where(g => g.Count() > 1)
-                .SelectMany(g => g.AsEnumerable())
-                .ToArray();
-
-            foreach (var option in duplicateShortNameOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0044, option.Property.Locations.First()
-                ));
-            }
-
-            // Duplicate environment variable name
-            var duplicateEnvironmentVariableNameOptions = options
-                .Where(p => !string.IsNullOrWhiteSpace(p.EnvironmentVariableName))
-                .GroupBy(p => p.EnvironmentVariableName, StringComparer.Ordinal)
-                .Where(g => g.Count() > 1)
-                .SelectMany(g => g.AsEnumerable())
-                .ToArray();
-
-            foreach (var option in duplicateEnvironmentVariableNameOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0045, option.Property.Locations.First()
-                ));
-            }
-
-            // Invalid converter
-            var invalidConverterOptions = options
-                .Where(o =>
-                    o.Converter != null &&
-                    !o.Converter.AllInterfaces.Any(KnownSymbols.IsArgumentValueConverterInterface))
-                .ToArray();
-
-            foreach (var option in invalidConverterOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0046, option.Property.Locations.First()
-                ));
-            }
-
-            // Invalid validators
-            var invalidValidatorsOptions = options
-                .Where(o => !o.Validators.All(v => v.AllInterfaces.Any(KnownSymbols.IsArgumentValueValidatorInterface)))
-                .ToArray();
-
-            foreach (var option in invalidValidatorsOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0047, option.Property.Locations.First()
-                ));
-            }
-
-            // Non-letter first character in name
-            var nonLetterFirstCharacterInNameOptions = options
-                .Where(o => !string.IsNullOrWhiteSpace(o.Name) && !char.IsLetter(o.Name[0]))
-                .ToArray();
-
-            foreach (var option in nonLetterFirstCharacterInNameOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0048, option.Property.Locations.First()
-                ));
-            }
-
-            // Non-letter short name
-            var nonLetterShortNameOptions = options
-                .Where(o => o.ShortName != null && !char.IsLetter(o.ShortName.Value))
-                .ToArray();
-
-            foreach (var option in nonLetterShortNameOptions)
-            {
-                context.ReportDiagnostic(Diagnostic.Create(
-                    DiagnosticDescriptors.CliFx0049, option.Property.Locations.First()
-                ));
-            }
-        }
-
-        private static void CheckCommandType(SymbolAnalysisContext context)
-        {
-            // Named type: MyCommand
-            if (!(context.Symbol is INamedTypeSymbol namedTypeSymbol) ||
-                namedTypeSymbol.TypeKind != TypeKind.Class)
-                return;
-
-            // Implements ICommand?
-            var implementsCommandInterface = namedTypeSymbol
-                .AllInterfaces
-                .Any(KnownSymbols.IsCommandInterface);
-
-            // Has CommandAttribute?
-            var hasCommandAttribute = namedTypeSymbol
-                .GetAttributes()
-                .Select(a => a.AttributeClass)
-                .Any(KnownSymbols.IsCommandAttribute);
-
-            var isValidCommandType =
-                // implements interface
-                implementsCommandInterface && (
-                    // and either abstract class or has attribute
-                    namedTypeSymbol.IsAbstract || hasCommandAttribute
-                );
-
-            if (!isValidCommandType)
-            {
-                // See if this was meant to be a command type (either interface or attribute present)
-                var isAlmostValidCommandType = implementsCommandInterface ^ hasCommandAttribute;
-
-                if (isAlmostValidCommandType && !implementsCommandInterface)
-                    context.ReportDiagnostic(Diagnostic.Create(DiagnosticDescriptors.CliFx0001,
-                        namedTypeSymbol.Locations.First()));
-
-                if (isAlmostValidCommandType && !hasCommandAttribute)
-                    context.ReportDiagnostic(Diagnostic.Create(DiagnosticDescriptors.CliFx0002,
-                        namedTypeSymbol.Locations.First()));
-
-                return;
-            }
-
-            var properties = namedTypeSymbol
-                .GetMembers()
-                .Where(m => m.Kind == SymbolKind.Property)
-                .OfType<IPropertySymbol>().ToArray();
-
-            // Check parameters
-            var parameterProperties = properties
-                .Where(p => p
-                    .GetAttributes()
-                    .Select(a => a.AttributeClass)
-                    .Any(KnownSymbols.IsCommandParameterAttribute))
-                .ToArray();
-
-            CheckCommandParameterProperties(context, parameterProperties);
-
-            // Check options
-            var optionsProperties = properties
-                .Where(p => p
-                    .GetAttributes()
-                    .Select(a => a.AttributeClass)
-                    .Any(KnownSymbols.IsCommandOptionAttribute))
-                .ToArray();
-
-            CheckCommandOptionProperties(context, optionsProperties);
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            context.EnableConcurrentExecution();
-            context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
-
-            context.RegisterSymbolAction(CheckCommandType, SymbolKind.NamedType);
-        }
-    }
-}

CliFx.Analyzers/ConsoleUsageAnalyzer.cs

@@ -1,74 +0,0 @@
-using System.Collections.Immutable;
-using System.Linq;
-using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.CSharp;
-using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Diagnostics;
-
-namespace CliFx.Analyzers
-{
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
-    public class ConsoleUsageAnalyzer : DiagnosticAnalyzer
-    {
-        public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(
-            DiagnosticDescriptors.CliFx0100
-        );
-
-        private static bool IsSystemConsoleInvocation(
-            SyntaxNodeAnalysisContext context,
-            InvocationExpressionSyntax invocationSyntax)
-        {
-            if (invocationSyntax.Expression is MemberAccessExpressionSyntax memberAccessSyntax &&
-                context.SemanticModel.GetSymbolInfo(memberAccessSyntax).Symbol is IMethodSymbol methodSymbol)
-            {
-                // Direct call to System.Console (e.g. System.Console.WriteLine())
-                if (KnownSymbols.IsSystemConsole(methodSymbol.ContainingType))
-                {
-                    return true;
-                }
-
-                // Indirect call to System.Console (e.g. System.Console.Error.WriteLine())
-                if (memberAccessSyntax.Expression is MemberAccessExpressionSyntax parentMemberAccessSyntax &&
-                    context.SemanticModel.GetSymbolInfo(parentMemberAccessSyntax).Symbol is IPropertySymbol propertySymbol)
-                {
-                    return KnownSymbols.IsSystemConsole(propertySymbol.ContainingType);
-                }
-            }
-
-            return false;
-        }
-
-        private static void CheckSystemConsoleUsage(SyntaxNodeAnalysisContext context)
-        {
-            if (context.Node is InvocationExpressionSyntax invocationSyntax &&
-                IsSystemConsoleInvocation(context, invocationSyntax))
-            {
-                // Check if IConsole is available in scope as alternative to System.Console
-                var isConsoleInterfaceAvailable = invocationSyntax
-                    .Ancestors()
-                    .OfType<MethodDeclarationSyntax>()
-                    .SelectMany(m => m.ParameterList.Parameters)
-                    .Select(p => p.Type)
-                    .Select(t => context.SemanticModel.GetSymbolInfo(t).Symbol)
-                    .Where(s => s != null)
-                    .Any(KnownSymbols.IsConsoleInterface!);
-
-                if (isConsoleInterfaceAvailable)
-                {
-                    context.ReportDiagnostic(Diagnostic.Create(
-                        DiagnosticDescriptors.CliFx0100,
-                        invocationSyntax.GetLocation()
-                    ));
-                }
-            }
-        }
-
-        public override void Initialize(AnalysisContext context)
-        {
-            context.EnableConcurrentExecution();
-            context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
-
-            context.RegisterSyntaxNodeAction(CheckSystemConsoleUsage, SyntaxKind.InvocationExpression);
-        }
-    }
-}

CliFx.Analyzers/DiagnosticDescriptors.cs

@@ -1,133 +0,0 @@
-using Microsoft.CodeAnalysis;
-
-namespace CliFx.Analyzers
-{
-    public static class DiagnosticDescriptors
-    {
-        public static readonly DiagnosticDescriptor CliFx0001 =
-            new DiagnosticDescriptor(nameof(CliFx0001),
-                "Type must implement the 'CliFx.ICommand' interface in order to be a valid command",
-                "Type must implement the 'CliFx.ICommand' interface in order to be a valid command",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0002 =
-            new DiagnosticDescriptor(nameof(CliFx0002),
-                "Type must be annotated with the 'CliFx.Attributes.CommandAttribute' in order to be a valid command",
-                "Type must be annotated with the 'CliFx.Attributes.CommandAttribute' in order to be a valid command",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0021 =
-            new DiagnosticDescriptor(nameof(CliFx0021),
-                "Parameter order must be unique within its command",
-                "Parameter order must be unique within its command",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0022 =
-            new DiagnosticDescriptor(nameof(CliFx0022),
-                "Parameter order must have unique name within its command",
-                "Parameter order must have unique name within its command",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0023 =
-            new DiagnosticDescriptor(nameof(CliFx0023),
-                "Only one non-scalar parameter per command is allowed",
-                "Only one non-scalar parameter per command is allowed",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0024 =
-            new DiagnosticDescriptor(nameof(CliFx0024),
-                "Non-scalar parameter must be last in order",
-                "Non-scalar parameter must be last in order",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0025 =
-            new DiagnosticDescriptor(nameof(CliFx0025),
-                "Parameter converter must implement 'CliFx.IArgumentValueConverter'",
-                "Parameter converter must implement 'CliFx.IArgumentValueConverter'",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0026 =
-            new DiagnosticDescriptor(nameof(CliFx0026),
-                "Parameter validator must implement 'CliFx.ArgumentValueValidator<T>'",
-                "Parameter validator must implement 'CliFx.ArgumentValueValidator<T>'",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0041 =
-            new DiagnosticDescriptor(nameof(CliFx0041),
-                "Option must have a name or short name specified",
-                "Option must have a name or short name specified",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0042 =
-            new DiagnosticDescriptor(nameof(CliFx0042),
-                "Option name must be at least 2 characters long",
-                "Option name must be at least 2 characters long",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0043 =
-            new DiagnosticDescriptor(nameof(CliFx0043),
-                "Option name must be unique within its command",
-                "Option name must be unique within its command",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0044 =
-            new DiagnosticDescriptor(nameof(CliFx0044),
-                "Option short name must be unique within its command",
-                "Option short name must be unique within its command",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0045 =
-            new DiagnosticDescriptor(nameof(CliFx0045),
-                "Option environment variable name must be unique within its command",
-                "Option environment variable name must be unique within its command",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0046 =
-            new DiagnosticDescriptor(nameof(CliFx0046),
-                "Option converter must implement 'CliFx.IArgumentValueConverter'",
-                "Option converter must implement 'CliFx.IArgumentValueConverter'",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0047 =
-            new DiagnosticDescriptor(nameof(CliFx0047),
-                "Option validator must implement 'CliFx.ArgumentValueValidator<T>'",
-                "Option validator must implement 'CliFx.ArgumentValueValidator<T>'",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0048 =
-            new DiagnosticDescriptor(nameof(CliFx0048),
-                "Option name must begin with a letter character.",
-                "Option name must begin with a letter character.",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0049 =
-            new DiagnosticDescriptor(nameof(CliFx0049),
-                "Option short name must be a letter character.",
-                "Option short name must be a letter character.",
-                "Usage", DiagnosticSeverity.Error, true
-            );
-
-        public static readonly DiagnosticDescriptor CliFx0100 =
-            new DiagnosticDescriptor(nameof(CliFx0100),
-                "Use the provided IConsole abstraction instead of System.Console to ensure that the command can be tested in isolation",
-                "Use the provided IConsole abstraction instead of System.Console to ensure that the command can be tested in isolation",
-                "Usage", DiagnosticSeverity.Warning, true
-            );
-    }
-}

CliFx.Analyzers/Internal/RoslynExtensions.cs

@@ -1,11 +0,0 @@
-using System;
-using Microsoft.CodeAnalysis;
-
-namespace CliFx.Analyzers.Internal
-{
-    internal static class RoslynExtensions
-    {
-        public static bool DisplayNameMatches(this ISymbol symbol, string name) =>
-            string.Equals(symbol.ToDisplayString(), name, StringComparison.Ordinal);
-    }
-}

CliFx.Analyzers/KnownSymbols.cs

@@ -1,43 +0,0 @@
-using CliFx.Analyzers.Internal;
-using Microsoft.CodeAnalysis;
-
-namespace CliFx.Analyzers
-{
-    internal static class KnownSymbols
-    {
-        public static bool IsSystemString(ISymbol symbol) =>
-            symbol.DisplayNameMatches("string") ||
-            symbol.DisplayNameMatches("System.String");
-
-        public static bool IsSystemChar(ISymbol symbol) =>
-            symbol.DisplayNameMatches("char") ||
-            symbol.DisplayNameMatches("System.Char");
-
-        public static bool IsSystemCollectionsGenericIEnumerable(ISymbol symbol) =>
-            symbol.DisplayNameMatches("System.Collections.Generic.IEnumerable<T>");
-
-        public static bool IsSystemConsole(ISymbol symbol) =>
-            symbol.DisplayNameMatches("System.Console");
-
-        public static bool IsConsoleInterface(ISymbol symbol) =>
-            symbol.DisplayNameMatches("CliFx.IConsole");
-
-        public static bool IsCommandInterface(ISymbol symbol) =>
-            symbol.DisplayNameMatches("CliFx.ICommand");
-
-        public static bool IsArgumentValueConverterInterface(ISymbol symbol) =>
-            symbol.DisplayNameMatches("CliFx.IArgumentValueConverter");
-
-        public static bool IsArgumentValueValidatorInterface(ISymbol symbol) =>
-            symbol.DisplayNameMatches("CliFx.IArgumentValueValidator");
-
-        public static bool IsCommandAttribute(ISymbol symbol) =>
-            symbol.DisplayNameMatches("CliFx.Attributes.CommandAttribute");
-
-        public static bool IsCommandParameterAttribute(ISymbol symbol) =>
-            symbol.DisplayNameMatches("CliFx.Attributes.CommandParameterAttribute");
-
-        public static bool IsCommandOptionAttribute(ISymbol symbol) =>
-            symbol.DisplayNameMatches("CliFx.Attributes.CommandOptionAttribute");
-    }
-}

CliFx.Analyzers/ObjectModel/CommandOptionSymbol.cs

@@ -0,0 +1,81 @@
+using System.Collections.Generic;
+using Microsoft.CodeAnalysis;
+using System.Linq;
+using CliFx.Analyzers.Utils.Extensions;
+
+namespace CliFx.Analyzers.ObjectModel;
+
+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)
+    {
+        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

@@ -0,0 +1,90 @@
+using System.Collections.Generic;
+using System.Linq;
+using CliFx.Analyzers.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.Analyzers.ObjectModel;
+
+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)
+    {
+        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

@@ -0,0 +1,14 @@
+namespace CliFx.Analyzers.ObjectModel;
+
+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>";
+}

CliFx.Analyzers/OptionMustBeInsideCommandAnalyzer.cs

@@ -0,0 +1,50 @@
+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 OptionMustBeInsideCommandAnalyzer : AnalyzerBase
+{
+    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)
+        {
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/OptionMustHaveNameOrShortNameAnalyzer.cs

@@ -0,0 +1,39 @@
+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 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.")
+    {
+    }
+
+    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)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/OptionMustHaveUniqueNameAnalyzer.cs

@@ -0,0 +1,64 @@
+using System;
+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 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).")
+    {
+    }
+
+    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;
+
+            if (string.IsNullOrWhiteSpace(otherOption.Name))
+                continue;
+
+            if (string.Equals(option.Name, otherOption.Name, StringComparison.OrdinalIgnoreCase))
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/OptionMustHaveUniqueShortNameAnalyzer.cs

@@ -0,0 +1,63 @@
+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 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).")
+    {
+    }
+
+    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;
+
+            if (otherOption.ShortName is null)
+                continue;
+
+            if (option.ShortName == otherOption.ShortName)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/OptionMustHaveValidConverterAnalyzer.cs

@@ -0,0 +1,49 @@
+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 OptionMustHaveValidConverterAnalyzer : AnalyzerBase
+{
+    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)
+        {
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/OptionMustHaveValidNameAnalyzer.cs

@@ -0,0 +1,42 @@
+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 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.")
+    {
+    }
+
+    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);
+    }
+}

CliFx.Analyzers/OptionMustHaveValidShortNameAnalyzer.cs

@@ -0,0 +1,42 @@
+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 OptionMustHaveValidShortNameAnalyzer : AnalyzerBase
+{
+    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))
+        {
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/OptionMustHaveValidValidatorsAnalyzer.cs

@@ -0,0 +1,51 @@
+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 OptionMustHaveValidValidatorsAnalyzer : AnalyzerBase
+{
+    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;
+
+        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)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+
+                // No need to report multiple identical diagnostics on the same node
+                break;
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustBeInsideCommandAnalyzer.cs

@@ -0,0 +1,50 @@
+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 ParameterMustBeInsideCommandAnalyzer : AnalyzerBase
+{
+    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)
+        {
+            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

@@ -0,0 +1,67 @@
+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 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).")
+    {
+    }
+
+    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;
+
+            if (otherParameter.Order > parameter.Order)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    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

@@ -0,0 +1,65 @@
+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 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.")
+    {
+    }
+
+    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;
+
+            if (!IsScalar(otherProperty.Type))
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustHaveUniqueNameAnalyzer.cs

@@ -0,0 +1,64 @@
+using System;
+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 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).")
+    {
+    }
+
+    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;
+
+            if (string.IsNullOrWhiteSpace(otherParameter.Name))
+                continue;
+
+            if (string.Equals(parameter.Name, otherParameter.Name, StringComparison.OrdinalIgnoreCase))
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustHaveUniqueOrderAnalyzer.cs

@@ -0,0 +1,57 @@
+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 ParameterMustHaveUniqueOrderAnalyzer : AnalyzerBase
+{
+    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;
+
+            if (parameter.Order == otherParameter.Order)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustHaveValidConverterAnalyzer.cs

@@ -0,0 +1,49 @@
+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 ParameterMustHaveValidConverterAnalyzer : AnalyzerBase
+{
+    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)
+        {
+            context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustHaveValidValidatorsAnalyzer.cs

@@ -0,0 +1,51 @@
+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 ParameterMustHaveValidValidatorsAnalyzer : AnalyzerBase
+{
+    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;
+
+        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)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+
+                // No need to report multiple identical diagnostics on the same node
+                break;
+            }
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/SystemConsoleShouldBeAvoidedAnalyzer.cs

@@ -0,0 +1,77 @@
+using System.Linq;
+using CliFx.Analyzers.ObjectModel;
+using CliFx.Analyzers.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace CliFx.Analyzers;
+
+[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)
+    {
+    }
+
+    private MemberAccessExpressionSyntax? TryGetSystemConsoleMemberAccess(
+        SyntaxNodeAnalysisContext context,
+        SyntaxNode node)
+    {
+        var currentNode = node;
+
+        while (currentNode is MemberAccessExpressionSyntax memberAccess)
+        {
+            var member = context.SemanticModel.GetSymbolInfo(memberAccess).Symbol;
+
+            if (member?.ContainingType?.DisplayNameMatches("System.Console") == true)
+            {
+                return memberAccess;
+            }
+
+            // Get inner expression, which may be another member access expression.
+            // Example: System.Console.Error
+            //          ~~~~~~~~~~~~~~          <- inner member access expression
+            //          --------------------    <- outer member access expression
+            currentNode = memberAccess.Expression;
+        }
+
+        return null;
+    }
+
+    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)
+        {
+            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

@@ -0,0 +1,52 @@
+using System;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace CliFx.Analyzers.Utils.Extensions;
+
+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)
+    {
+        analysisContext.RegisterSyntaxNodeAction(ctx =>
+        {
+            if (ctx.Node is not ClassDeclarationSyntax classDeclaration)
+                return;
+
+            var type = ctx.SemanticModel.GetDeclaredSymbol(classDeclaration);
+            if (type is null)
+                return;
+
+            analyze(ctx, classDeclaration, type);
+        }, SyntaxKind.ClassDeclaration);
+    }
+
+    public static void HandlePropertyDeclaration(
+        this AnalysisContext analysisContext,
+        Action<SyntaxNodeAnalysisContext, PropertyDeclarationSyntax, IPropertySymbol> analyze)
+    {
+        analysisContext.RegisterSyntaxNodeAction(ctx =>
+        {
+            if (ctx.Node is not PropertyDeclarationSyntax propertyDeclaration)
+                return;
+
+            var property = ctx.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
+            if (property is null)
+                return;
+
+            analyze(ctx, propertyDeclaration, property);
+        }, SyntaxKind.PropertyDeclaration);
+    }
+}

CliFx.Analyzers/Utils/Extensions/StringExtensions.cs

@@ -0,0 +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);
+
+        return str;
+    }
+}

CliFx.Benchmarks/Benchmarks.CliFx.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using BenchmarkDotNet.Attributes;
+using CliFx.Attributes;
+using CliFx.Infrastructure;
+
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
+{
+    [Command]
+    public class CliFxCommand : ICommand
+    {
+        [CommandOption("str", 's')]
+        public string? StrOption { get; set; }
+
+        [CommandOption("int", 'i')]
+        public int IntOption { 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>());
+}

CliFx.Benchmarks/Benchmarks.Clipr.cs

@@ -1,6 +1,9 @@
-using clipr;
+using BenchmarkDotNet.Attributes;
+using clipr;
 
-namespace CliFx.Benchmarks.Commands
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
     public class CliprCommand
     {
@@ -17,4 +20,7 @@ namespace CliFx.Benchmarks.Commands
         {
         }
     }
+
+    [Benchmark(Description = "Clipr")]
+    public void ExecuteWithClipr() => CliParser.Parse<CliprCommand>(Arguments).Execute();
 }

CliFx.Benchmarks/Benchmarks.Cocona.cs

@@ -1,6 +1,9 @@
-using Cocona;
+using BenchmarkDotNet.Attributes;
+using Cocona;
 
-namespace CliFx.Benchmarks.Commands
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
     public class CoconaCommand
     {
@@ -14,4 +17,7 @@ namespace CliFx.Benchmarks.Commands
         {
         }
     }
+
+    [Benchmark(Description = "Cocona")]
+    public void ExecuteWithCocona() => CoconaApp.Run<CoconaCommand>(Arguments);
 }

CliFx.Benchmarks/Benchmarks.CommandLineParser.cs

@@ -0,0 +1,29 @@
+using BenchmarkDotNet.Attributes;
+using CommandLine;
+
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
+{
+    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()
+        {
+        }
+    }
+
+    [Benchmark(Description = "CommandLineParser")]
+    public void ExecuteWithCommandLineParser() =>
+        new Parser()
+            .ParseArguments(Arguments, typeof(CommandLineParserCommand))
+            .WithParsed<CommandLineParserCommand>(c => c.Execute());
+}

CliFx.Benchmarks/Benchmarks.McMaster.cs

@@ -0,0 +1,24 @@
+using BenchmarkDotNet.Attributes;
+using McMaster.Extensions.CommandLineUtils;
+
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
+{
+    public class McMasterCommand
+    {
+        [Option("--str|-s")]
+        public string? StrOption { get; set; }
+
+        [Option("--int|-i")]
+        public int IntOption { 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);
+}

CliFx.Benchmarks/Benchmarks.PowerArgs.cs

@@ -1,6 +1,9 @@
-using PowerArgs;
+using BenchmarkDotNet.Attributes;
+using PowerArgs;
 
-namespace CliFx.Benchmarks.Commands
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
     public class PowerArgsCommand
     {
@@ -17,4 +20,7 @@ namespace CliFx.Benchmarks.Commands
         {
         }
     }
+
+    [Benchmark(Description = "PowerArgs")]
+    public void ExecuteWithPowerArgs() => Args.InvokeMain<PowerArgsCommand>(Arguments);
 }

CliFx.Benchmarks/Benchmarks.SystemCommandLine.cs

@@ -1,8 +1,11 @@
 using System.CommandLine;
 using System.CommandLine.Invocation;
 using System.Threading.Tasks;
+using BenchmarkDotNet.Attributes;
 
-namespace CliFx.Benchmarks.Commands
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
     public class SystemCommandLineCommand
     {
@@ -26,9 +29,15 @@ namespace CliFx.Benchmarks.Commands
                 }
             };
 
-            command.Handler = CommandHandler.Create(typeof(SystemCommandLineCommand).GetMethod(nameof(ExecuteHandler)));
+            command.Handler = CommandHandler.Create(
+                typeof(SystemCommandLineCommand).GetMethod(nameof(ExecuteHandler))!
+            );
 
             return command.InvokeAsync(args);
         }
     }
+
+    [Benchmark(Description = "System.CommandLine")]
+    public async Task<int> ExecuteWithSystemCommandLine() =>
+        await new SystemCommandLineCommand().ExecuteAsync(Arguments);
 }

CliFx.Benchmarks/Benchmarks.cs

@@ -1,52 +1,19 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Configs;
 using BenchmarkDotNet.Order;
 using BenchmarkDotNet.Running;
-using CliFx.Benchmarks.Commands;
-using CommandLine;
 
-namespace CliFx.Benchmarks
-{
-    [SimpleJob]
+namespace CliFx.Benchmarks;
+
 [RankColumn]
 [Orderer(SummaryOrderPolicy.FastestToSlowest)]
-    public class Benchmarks
+public partial class Benchmarks
 {
     private static readonly string[] Arguments = {"--str", "hello world", "-i", "13", "-b"};
 
-        [Benchmark(Description = "CliFx", Baseline = true)]
-        public async ValueTask<int> ExecuteWithCliFx() =>
-            await new CliApplicationBuilder().AddCommand<CliFxCommand>().Build().RunAsync(Arguments, new Dictionary<string, string>());
-
-        [Benchmark(Description = "System.CommandLine")]
-        public async Task<int> ExecuteWithSystemCommandLine() =>
-            await new SystemCommandLineCommand().ExecuteAsync(Arguments);
-
-        [Benchmark(Description = "McMaster.Extensions.CommandLineUtils")]
-        public int ExecuteWithMcMaster() =>
-            McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute<McMasterCommand>(Arguments);
-
-        [Benchmark(Description = "CommandLineParser")]
-        public void ExecuteWithCommandLineParser() =>
-            new Parser()
-                .ParseArguments(Arguments, typeof(CommandLineParserCommand))
-                .WithParsed<CommandLineParserCommand>(c => c.Execute());
-
-        [Benchmark(Description = "PowerArgs")]
-        public void ExecuteWithPowerArgs() =>
-            PowerArgs.Args.InvokeMain<PowerArgsCommand>(Arguments);
-
-        [Benchmark(Description = "Clipr")]
-        public void ExecuteWithClipr() =>
-            clipr.CliParser.Parse<CliprCommand>(Arguments).Execute();
-
-        [Benchmark(Description = "Cocona")]
-        public void ExecuteWithCocona() =>
-            Cocona.CoconaApp.Run<CoconaCommand>(Arguments);
-
-        public static void Main() =>
-            BenchmarkRunner.Run<Benchmarks>(DefaultConfig.Instance.With(ConfigOptions.DisableOptimizationsValidator));
-    }
+    public static void Main() => BenchmarkRunner.Run<Benchmarks>(
+        DefaultConfig
+            .Instance
+            .WithOptions(ConfigOptions.DisableOptimizationsValidator)
+    );
 }

CliFx.Benchmarks/CliFx.Benchmarks.csproj

@@ -1,19 +1,18 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <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="3.0.0" />
+    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="4.0.0" />
     <PackageReference Include="PowerArgs" Version="3.6.0" />
-    <PackageReference Include="System.CommandLine.Experimental" Version="0.3.0-alpha.19317.1" />
+    <PackageReference Include="System.CommandLine" Version="2.0.0-beta1.20574.7" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Benchmarks/Commands/CliFxCommand.cs

@@ -1,20 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Benchmarks.Commands
-{
-    [Command]
-    public class CliFxCommand : ICommand
-    {
-        [CommandOption("str", 's')]
-        public string? StrOption { get; set; }
-
-        [CommandOption("int", 'i')]
-        public int IntOption { get; set; }
-
-        [CommandOption("bool", 'b')]
-        public bool BoolOption { get; set; }
-
-        public ValueTask ExecuteAsync(IConsole console) => default;
-    }
-}

CliFx.Benchmarks/Commands/CommandLineParserCommand.cs

@@ -1,20 +0,0 @@
-using CommandLine;
-
-namespace CliFx.Benchmarks.Commands
-{
-    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()
-        {
-        }
-    }
-}

CliFx.Benchmarks/Commands/McMasterCommand.cs

@@ -1,18 +0,0 @@
-using McMaster.Extensions.CommandLineUtils;
-
-namespace CliFx.Benchmarks.Commands
-{
-    public class McMasterCommand
-    {
-        [Option("--str|-s")]
-        public string? StrOption { get; set; }
-
-        [Option("--int|-i")]
-        public int IntOption { get; set; }
-
-        [Option("--bool|-b")]
-        public bool BoolOption { get; set; }
-
-        public int OnExecute() => 0;
-    }
-}

CliFx.Benchmarks/Readme.md

@@ -0,0 +1,22 @@
+## CliFx.Benchmarks
+
+All benchmarks below were ran with the following configuration:
+
+```ini
+BenchmarkDotNet=v0.12.0, OS=Windows 10.0.14393.3443 (1607/AnniversaryUpdate/Redstone1)
+Intel Core i5-4460 CPU 3.20GHz (Haswell), 1 CPU, 4 logical and 4 physical cores
+Frequency=3124994 Hz, Resolution=320.0006 ns, Timer=TSC
+.NET Core SDK=3.1.100
+  [Host]     : .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT
+  DefaultJob : .NET Core 3.1.0 (CoreCLR 4.700.19.56402, CoreFX 4.700.19.56404), X64 RyuJIT
+```
+
+| Method                               |        Mean |     Error |     StdDev | Ratio | RatioSD | Rank |
+| ------------------------------------ | ----------: | --------: | ---------: | ----: | ------: | ---: |
+| CommandLineParser                    |    24.79 us |  0.166 us |   0.155 us |  0.49 |    0.00 |    1 |
+| CliFx                                |    50.27 us |  0.248 us |   0.232 us |  1.00 |    0.00 |    2 |
+| Clipr                                |   160.22 us |  0.817 us |   0.764 us |  3.19 |    0.02 |    3 |
+| McMaster.Extensions.CommandLineUtils |   166.45 us |  1.111 us |   1.039 us |  3.31 |    0.03 |    4 |
+| System.CommandLine                   |   170.27 us |  0.599 us |   0.560 us |  3.39 |    0.02 |    5 |
+| PowerArgs                            |   306.12 us |  1.495 us |   1.398 us |  6.09 |    0.03 |    6 |
+| Cocona                               | 1,856.07 us | 48.727 us | 141.367 us | 37.88 |    2.60 |    7 |

CliFx.Demo/CliFx.Demo.csproj

@@ -1,14 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="3.1.9" />
-    <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

@@ -1,45 +1,45 @@
 using System;
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Internal;
-using CliFx.Demo.Models;
-using CliFx.Demo.Services;
+using CliFx.Demo.Domain;
+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
 {
-        private readonly LibraryService _libraryService;
+    private readonly LibraryProvider _libraryProvider;
 
     [CommandParameter(0, Name = "title", Description = "Book title.")]
-        public string Title { get; set; } = "";
+    public string Title { get; init; } = "";
 
     [CommandOption("author", 'a', IsRequired = true, Description = "Book author.")]
-        public string Author { get; set; } = "";
+    public string Author { get; init; } = "";
 
     [CommandOption("published", 'p', Description = "Book publish date.")]
-        public DateTimeOffset Published { get; set; } = CreateRandomDate();
+    public DateTimeOffset Published { get; init; } = CreateRandomDate();
 
     [CommandOption("isbn", 'n', Description = "Book ISBN.")]
-        public Isbn Isbn { get; set; } = CreateRandomIsbn();
+    public Isbn Isbn { get; init; } = CreateRandomIsbn();
 
-        public BookAddCommand(LibraryService libraryService)
+    public BookAddCommand(LibraryProvider libraryProvider)
     {
-            _libraryService = libraryService;
+        _libraryProvider = libraryProvider;
     }
 
     public ValueTask ExecuteAsync(IConsole console)
     {
-            if (_libraryService.GetBook(Title) != null)
-                throw new CommandException("Book already exists.", 1);
+        if (_libraryProvider.TryGetBook(Title) is not null)
+            throw new CommandException("Book already exists.", 10);
 
         var book = new Book(Title, Author, Published, Isbn);
-            _libraryService.AddBook(book);
+        _libraryProvider.AddBook(book);
 
         console.Output.WriteLine("Book added.");
-            console.RenderBook(book);
+        console.Output.WriteBook(book);
 
         return default;
     }
@@ -47,22 +47,23 @@ namespace CliFx.Demo.Commands
 
 public partial class BookAddCommand
 {
-        private static readonly Random Random = new Random();
+    private static readonly Random Random = new();
 
-        private static DateTimeOffset CreateRandomDate() => new DateTimeOffset(
+    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);
+        TimeSpan.Zero
+    );
 
-        private static Isbn CreateRandomIsbn() => new Isbn(
+    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));
-    }
+        Random.Next(0, 9)
+    );
 }

CliFx.Demo/Commands/BookCommand.cs

@@ -1,34 +1,34 @@
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Internal;
-using CliFx.Demo.Services;
+using CliFx.Demo.Domain;
+using CliFx.Demo.Utils;
 using CliFx.Exceptions;
+using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
-{
-    [Command("book", Description = "View, list, add or remove books.")]
+namespace CliFx.Demo.Commands;
+
+[Command("book", Description = "Retrieve a book from the library.")]
 public class BookCommand : ICommand
 {
-        private readonly LibraryService _libraryService;
+    private readonly LibraryProvider _libraryProvider;
 
-        [CommandParameter(0, Name = "title", Description = "Book title.")]
-        public string Title { get; set; } = "";
+    [CommandParameter(0, Name = "title", Description = "Title of the book to retrieve.")]
+    public string Title { get; init; } = "";
 
-        public BookCommand(LibraryService libraryService)
+    public BookCommand(LibraryProvider libraryProvider)
     {
-            _libraryService = libraryService;
+        _libraryProvider = libraryProvider;
     }
 
     public ValueTask ExecuteAsync(IConsole console)
     {
-            var book = _libraryService.GetBook(Title);
+        var book = _libraryProvider.TryGetBook(Title);
 
-            if (book == null)
-                throw new CommandException("Book not found.", 1);
+        if (book is null)
+            throw new CommandException("Book not found.", 10);
 
-            console.RenderBook(book);
+        console.Output.WriteBook(book);
 
         return default;
     }
 }
-}

CliFx.Demo/Commands/BookListCommand.cs

@@ -1,37 +1,36 @@
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Internal;
-using CliFx.Demo.Services;
+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
 {
-        private readonly LibraryService _libraryService;
+    private readonly LibraryProvider _libraryProvider;
 
-        public BookListCommand(LibraryService libraryService)
+    public BookListCommand(LibraryProvider libraryProvider)
     {
-            _libraryService = libraryService;
+        _libraryProvider = libraryProvider;
     }
 
     public ValueTask ExecuteAsync(IConsole console)
     {
-            var library = _libraryService.GetLibrary();
+        var library = _libraryProvider.GetLibrary();
 
-            var isFirst = true;
-            foreach (var book in library.Books)
+        for (var i = 0; i < library.Books.Count; i++)
         {
-                // Margin
-                if (!isFirst)
+            // Add margin
+            if (i != 0)
                 console.Output.WriteLine();
-                isFirst = false;
 
             // Render book
-                console.RenderBook(book);
+            var book = library.Books[i];
+            console.Output.WriteBook(book);
         }
 
         return default;
     }
 }
-}

CliFx.Demo/Commands/BookRemoveCommand.cs

@@ -1,35 +1,35 @@
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Services;
+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
 {
-        private readonly LibraryService _libraryService;
+    private readonly LibraryProvider _libraryProvider;
 
-        [CommandParameter(0, Name = "title", Description = "Book title.")]
-        public string Title { get; set; } = "";
+    [CommandParameter(0, Name = "title", Description = "Title of the book to remove.")]
+    public string Title { get; init; } = "";
 
-        public BookRemoveCommand(LibraryService libraryService)
+    public BookRemoveCommand(LibraryProvider libraryProvider)
     {
-            _libraryService = libraryService;
+        _libraryProvider = libraryProvider;
     }
 
     public ValueTask ExecuteAsync(IConsole console)
     {
-            var book = _libraryService.GetBook(Title);
+        var book = _libraryProvider.TryGetBook(Title);
 
-            if (book == null)
-                throw new CommandException("Book not found.", 1);
+        if (book is null)
+            throw new CommandException("Book not found.", 10);
 
-            _libraryService.RemoveBook(book);
+        _libraryProvider.RemoveBook(book);
 
         console.Output.WriteLine($"Book {Title} removed.");
 
         return default;
     }
 }
-}

CliFx.Demo/Domain/Book.cs

@@ -0,0 +1,22 @@
+using System;
+
+namespace CliFx.Demo.Domain;
+
+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)
+    {
+        Title = title;
+        Author = author;
+        Published = published;
+        Isbn = isbn;
+    }
+}

CliFx.Demo/Domain/Isbn.cs

@@ -0,0 +1,44 @@
+using System;
+
+namespace CliFx.Demo.Domain;
+
+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)
+    {
+        EanPrefix = eanPrefix;
+        RegistrationGroup = registrationGroup;
+        Registrant = registrant;
+        Publication = publication;
+        CheckDigit = checkDigit;
+    }
+
+    public override string ToString() =>
+        $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
+}
+
+public partial class Isbn
+{
+    public 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

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace CliFx.Demo.Domain;
+
+public partial class Library
+{
+    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);
+    }
+}
+
+public partial class Library
+{
+    public static Library Empty { get; } = new(Array.Empty<Book>());
+}

CliFx.Demo/Domain/LibraryProvider.cs

@@ -0,0 +1,40 @@
+using System.IO;
+using System.Linq;
+using Newtonsoft.Json;
+
+namespace CliFx.Demo.Domain;
+
+public class LibraryProvider
+{
+    private static string StorageFilePath { get; } = Path.Combine(Directory.GetCurrentDirectory(), "Library.json");
+
+    private void StoreLibrary(Library library)
+    {
+        var data = JsonConvert.SerializeObject(library);
+        File.WriteAllText(StorageFilePath, data);
+    }
+
+    public Library GetLibrary()
+    {
+        if (!File.Exists(StorageFilePath))
+            return Library.Empty;
+
+        var data = File.ReadAllText(StorageFilePath);
+
+        return JsonConvert.DeserializeObject<Library>(data) ?? Library.Empty;
+    }
+
+    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 RemoveBook(Book book)
+    {
+        var updatedLibrary = GetLibrary().WithoutBook(book);
+        StoreLibrary(updatedLibrary);
+    }
+}

CliFx.Demo/Internal/Extensions.cs

@@ -1,29 +0,0 @@
-using System;
-using CliFx.Demo.Models;
-
-namespace CliFx.Demo.Internal
-{
-    internal static class Extensions
-    {
-        public static void RenderBook(this IConsole console, Book book)
-        {
-            // Title
-            console.WithForegroundColor(ConsoleColor.White, () => console.Output.WriteLine(book.Title));
-
-            // Author
-            console.Output.Write("  ");
-            console.Output.Write("Author: ");
-            console.WithForegroundColor(ConsoleColor.White, () => console.Output.WriteLine(book.Author));
-
-            // Published
-            console.Output.Write("  ");
-            console.Output.Write("Published: ");
-            console.WithForegroundColor(ConsoleColor.White, () => console.Output.WriteLine($"{book.Published:d}"));
-
-            // ISBN
-            console.Output.Write("  ");
-            console.Output.Write("ISBN: ");
-            console.WithForegroundColor(ConsoleColor.White, () => console.Output.WriteLine(book.Isbn));
-        }
-    }
-}

CliFx.Demo/Models/Book.cs

@@ -1,23 +0,0 @@
-using System;
-
-namespace CliFx.Demo.Models
-{
-    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)
-        {
-            Title = title;
-            Author = author;
-            Published = published;
-            Isbn = isbn;
-        }
-    }
-}

CliFx.Demo/Models/Extensions.cs

@@ -1,22 +0,0 @@
-using System.Linq;
-
-namespace CliFx.Demo.Models
-{
-    public static class Extensions
-    {
-        public static Library WithBook(this Library library, Book book)
-        {
-            var books = library.Books.ToList();
-            books.Add(book);
-
-            return new Library(books);
-        }
-
-        public static Library WithoutBook(this Library library, Book book)
-        {
-            var books = library.Books.Where(b => b != book).ToArray();
-
-            return new Library(books);
-        }
-    }
-}

CliFx.Demo/Models/Isbn.cs

@@ -1,45 +0,0 @@
-using System;
-
-namespace CliFx.Demo.Models
-{
-    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)
-        {
-            EanPrefix = eanPrefix;
-            RegistrationGroup = registrationGroup;
-            Registrant = registrant;
-            Publication = publication;
-            CheckDigit = checkDigit;
-        }
-
-        public override string ToString() =>
-            $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
-    }
-
-    public partial class Isbn
-    {
-        public 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/Models/Library.cs

@@ -1,20 +0,0 @@
-using System;
-using System.Collections.Generic;
-
-namespace CliFx.Demo.Models
-{
-    public partial class Library
-    {
-        public IReadOnlyList<Book> Books { get; }
-
-        public Library(IReadOnlyList<Book> books)
-        {
-            Books = books;
-        }
-    }
-
-    public partial class Library
-    {
-        public static Library Empty { get; } = new Library(Array.Empty<Book>());
-    }
-}

CliFx.Demo/Program.cs

@@ -1,20 +1,13 @@
-using System;
-using System.Threading.Tasks;
+using CliFx;
 using CliFx.Demo.Commands;
-using CliFx.Demo.Services;
+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();
 
 // Register services
-            services.AddSingleton<LibraryService>();
+services.AddSingleton<LibraryProvider>();
 
 // Register commands
 services.AddTransient<BookCommand>();
@@ -22,14 +15,11 @@ namespace CliFx.Demo
 services.AddTransient<BookRemoveCommand>();
 services.AddTransient<BookListCommand>();
 
-            return services.BuildServiceProvider();
-        }
+var serviceProvider = services.BuildServiceProvider();
 
-        public static async Task<int> Main() =>
-            await new CliApplicationBuilder()
+return await new CliApplicationBuilder()
+    .SetDescription("Demo application showcasing CliFx features.")
     .AddCommandsFromThisAssembly()
-                .UseTypeActivator(GetServiceProvider().GetRequiredService)
+    .UseTypeActivator(serviceProvider.GetRequiredService)
     .Build()
     .RunAsync();
-    }
-}

CliFx.Demo/Readme.md

@@ -2,6 +2,4 @@
 
 Sample command line interface for managing a library of books.
 
-This demo project shows basic CliFx functionality such as command routing, argument parsing, autogenerated help text, and some other things.
-
-You can get a list of available commands by running `CliFx.Demo --help`.
+This demo project showcases basic CliFx functionality such as command routing, argument parsing, autogenerated help text.

CliFx.Demo/Services/LibraryService.cs

@@ -1,42 +0,0 @@
-using System.IO;
-using System.Linq;
-using CliFx.Demo.Models;
-using Newtonsoft.Json;
-
-namespace CliFx.Demo.Services
-{
-    public class LibraryService
-    {
-        private string StorageFilePath => Path.Combine(Directory.GetCurrentDirectory(), "Data.json");
-
-        private void StoreLibrary(Library library)
-        {
-            var data = JsonConvert.SerializeObject(library);
-            File.WriteAllText(StorageFilePath, data);
-        }
-
-        public Library GetLibrary()
-        {
-            if (!File.Exists(StorageFilePath))
-                return Library.Empty;
-
-            var data = File.ReadAllText(StorageFilePath);
-
-            return JsonConvert.DeserializeObject<Library>(data);
-        }
-
-        public Book? GetBook(string title) => GetLibrary().Books.FirstOrDefault(b => b.Title == title);
-
-        public void AddBook(Book book)
-        {
-            var updatedLibrary = GetLibrary().WithBook(book);
-            StoreLibrary(updatedLibrary);
-        }
-
-        public void RemoveBook(Book book)
-        {
-            var updatedLibrary = GetLibrary().WithoutBook(book);
-            StoreLibrary(updatedLibrary);
-        }
-    }
-}

CliFx.Demo/Utils/ConsoleExtensions.cs

@@ -0,0 +1,36 @@
+using System;
+using CliFx.Demo.Domain;
+using CliFx.Infrastructure;
+
+namespace CliFx.Demo.Utils;
+
+internal static class ConsoleExtensions
+{
+    public static void WriteBook(this ConsoleWriter writer, Book book)
+    {
+        // Title
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Title);
+
+        // Author
+        writer.Write("  ");
+        writer.Write("Author: ");
+
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Author);
+
+        // Published
+        writer.Write("  ");
+        writer.Write("Published: ");
+
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine($"{book.Published:d}");
+
+        // ISBN
+        writer.Write("  ");
+        writer.Write("ISBN: ");
+
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Isbn);
+    }
+}