Update version

Closes #135

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,8 @@
 blank_issues_enabled: false
 contact_links:
+  - name: ⚠ Feature request
+    url: https://github.com/Tyrrrz/.github/blob/master/docs/project-status.md
+    about: Sorry, but this project is in maintenance mode and no longer accepts new feature requests.
   - name: 💬 Discord server
     url: https://discord.gg/2SUWKFnHSm
     about: Chat with the project community.

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -1,22 +0,0 @@
-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/main.yml

@@ -6,7 +6,7 @@ jobs:
   main:
     uses: Tyrrrz/.github/.github/workflows/nuget.yml@master
     with:
-      dotnet-version: 6.0.x
+      dotnet-version: 7.0.x
     secrets:
       CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
       NUGET_TOKEN: ${{ secrets.NUGET_TOKEN }}

Changelog.md

@@ -1,14 +1,42 @@
-### v2.2.5 (10-May-2022)
+# Changelog
+
+## v2.3.4 (18-May-2023)
+
+- Added an overload of `CliApplicationBuilder.UseTypeActivator(...)` that accepts a `Func<IReadOnlyList<Type>, IServiceProvider>` delegate. The first parameter in the delegate is the list of all command types registered in the application. You can use this overload to more easily add the commands to a DI container. See the readme for an [updated example](https://github.com/Tyrrrz/CliFx/tree/2.3.4#type-activation).
+
+## v2.3.3 (28-Apr-2023)
+
+- Fixed an issue where the analyzers failed to load in some projects, due to targeting a Roslyn version that was too high.
+
+## v2.3.2 (06-Apr-2023)
+
+- Added name-based ordering to subcommands when displayed in the help text. (Thanks [@CartBlanche](https://github.com/CartBlanche))
+
+## v2.3.1 (08-Dec-2022)
+
+- Added support for the `required` keyword introduced in C# 11. Command options bound to required properties are now marked as required by default (equivalent to setting `IsRequired = true` on the attribute). Also added analyzers that prevent marking an option or parameter non-required if it's bound to a required property.
+
+## v2.3 (12-Jul-2022)
+
+- Added console dimension properties `WindowWidth` and `WindowHeight` to `IConsole` interface and implementing classes.
+- Improved inline documentation for members of `IConsole` interface.
+
+## v2.2.6 (14-Jun-2022)
+
+- Added an overload of `CliApplicationBuilder.UseTypeActivator(...)` that accepts an instance of `IServiceProvider`. This slightly simplifies integration with many DI containers.
+- Fixed minor grammar mistakes in user-facing error messages.
+
+## v2.2.5 (10-May-2022)
 
 - Updated default value resolution for the application executable name. It will now resolve to `myapp.exe` instead of `dotnet myapp.dll` when the application is launched through the EXE apphost on Windows. On other platforms, or when running the application through the .NET CLI, the behavior will be the same as before.
 
-### v2.2.4 (22-Apr-2022)
+## v2.2.4 (22-Apr-2022)
 
 - Added more contextual information to analyzer diagnostics.
 - Fixed an issue where the analyzer incorrectly reported an error on converters that didn't directly match the target type but were compatible through known built-in conversions.
 - Fixed an issue where MSBuild produced a lot of analyzer-related warnings in certain circumstances.
 
-### v2.2.3 (17-Apr-2022)
+## v2.2.3 (17-Apr-2022)
 
 - Changed method signature of `IConsole.ReadKey()` to return `ConsoleKeyInfo` instead of `void`. The return type was originally defined as `void` by mistake. This change is source-backwards-compatible but may break on binary level if you were previously calling this method indirectly (i.e. through a library).
 - Added `FakeConsole.EnqueueKey(...)` to facilitate the testing of `IConsole.ReadKey()`. You can use this method to simulate key presses in your application.
@@ -16,57 +44,57 @@
 - Improved diagnostics produced by analyzers. Where relevant, highlighted code is now limited to the property or type identifier, instead of the whole property or type declaration. Also extended the diagnostic messages with additional information.
 - Fixed an issue where throwing an exception inside a constructor of a command type resulted in an unrelated error message about the absence of a parameterless constructor.
 
-### v2.2.2 (30-Jan-2022)
+## v2.2.2 (30-Jan-2022)
 
 - Fixed an issue where `ConsoleWriter` and `ConsoleReader` were not properly thread-safe.
 - Fixed an issue where the analyzer failed to load under certain circumstances when running inside Visual Studio.
 
-### v2.2.1 (16-Jan-2022)
+## 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)
+## 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)
+## 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)
+## 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)
+## 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)
+## 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)
+## 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)
+## 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)
+## 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)
+## 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.
@@ -86,7 +114,7 @@
   - 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.
+- 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.
@@ -100,34 +128,34 @@
   - `ITypeActivator`/`DefaultTypeActivator`/`DelegateTypeActivator` moved from `CliFx` to `CliFx.Infrastructure`
   - `BindingValidator`/`BindingConverter` moved from `CliFx` to `CliFx.Extensibility`
 
-### v1.6 (06-Dec-2020)
+## 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))
 - Added `CliFx.ArgumentValueConverter<T>` class that you can inherit from to implement custom value converters. `CliFx.IArgumentValueConverter` interface is still available, but it is recommended to inherit from the generic class instead, due to the type safety it provides. The interface may become internal or get removed in one of the future major versions.
 - Updated requirements for option names and short names: short names now must be letter characters (lowercase or uppercase), while names must now start with a letter character. This means option names can no longer start with a digit or a special character. This change makes it possible to pass negative number values without the need to quote them, i.e. `--my-number -5`.
 
-### v1.5 (23-Oct-2020)
+## v1.5 (23-Oct-2020)
 
 - Added pretty-printing for unhandled exceptions thrown from within the application. This makes the errors easier to parse visually and should help in troubleshooting. This change does not affect `CommandException`, as it already has special treatment. (Thanks [@Mårten Åsberg](https://github.com/89netraM))
 - Added support for custom value converters. You can now create a type that implements `CliFx.IArgumentValueConverter` and specify it as a converter for your parameters or options via the `Converter` named property. This should enable conversion between raw argument values and custom types which are not string-initializable. (Thanks [@Oleksandr Shustov](https://github.com/AlexandrShustov))
 - Improved help text so that it also shows minimal usage examples for child and descendant commands, besides the actual command it was requested on. This should improve user experience for applications with many nested commands. (Thanks [@Nikiforov Alexey](https://github.com/NikiforovAll))
 
-### v1.4 (20-Aug-2020)
+## v1.4 (20-Aug-2020)
 
 - Added `VirtualConsole.CreateBuffered()` method to simplify test setup when using in-memory backing stores for output and error streams. Please refer to the readme for updated recommendations on how to test applications built with CliFx.
 - Added generic `CliApplicationBuilder.AddCommand<TCommand>()`. This overload simplifies adding commands one-by-one as it also checks that the type implements `ICommand`.
 
-### v1.3.2 (31-Jul-2020)
+## 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 `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)
+## v1.3.1 (19-Jul-2020)
 
 - Running the application with the debug directive (`myapp [debug]`) will now also try to launch a debugger instance. In most cases it will save time as you won't need to attach the debugger manually. (Thanks [@Volodymyr Shkolka](https://github.com/BlackGad))
 - Fixed an issue where unhandled generic exceptions (i.e. not `CommandException`) sometimes caused the application to incorrectly return successful exit code due to an overflow issue on Unix systems. Starting from this version, all unhandled generic exceptions will produce `1` as the exit code when thrown. Instances of `CommandException` can still be configured to return any specified exit code, but it's recommended to constrain the values between `1` and `255` to avoid overflow issues. (Thanks [@Ihor Nechyporuk](https://github.com/inech))
 
-### v1.3 (23-May-2020)
+## v1.3 (23-May-2020)
 
 - Changed analyzers to report errors instead of warnings. If you find that some analyzer works incorrectly, please report it on GitHub. You can also configure inspection severity overrides in your project if you need to.
 - Improved help text by showing default values for non-required options. This only works on types that have a custom override for `ToString()` method. Additionally, if the type implements `IFormattable`, the overload with a format provider will be used instead. (Thanks [@Domn Werner](https://github.com/domn1995))
@@ -135,7 +163,7 @@
 - Fixed an issue where it was possible to define a command with an option that has the same name or short name as built-in help or version options. Previously it would lead to the user-defined option being ignored in favor of the built-in option. Now this will throw an exception instead.
 - Changed the underlying representation of `StreamReader`/`StreamWriter` objects used in `SystemConsole` and `VirtualConsole` to be thread-safe.
 
-### v1.2 (11-May-2020)
+## v1.2 (11-May-2020)
 
 - Added built-in Roslyn analyzers that help catch incorrect usage of the library. Currently, all analyzers report issues as warnings so as to not prevent the project from building. In the future that may change.
 - Added an optional parameter to `new CommandException(...)` called `showHelp` which can be used to instruct CliFx to show help for the current command after printing the error. (Thanks [@Domn Werner](https://github.com/domn1995))
@@ -146,7 +174,7 @@
 - Improved exception messages.
 - Improved exceptions related to user input by also showing help text after the error message. (Thanks [@Domn Werner](https://github.com/domn1995))
 
-### v1.1 (16-Mar-2020)
+## v1.1 (16-Mar-2020)
 
 - Changed `IConsole` interface (and as a result, `SystemConsole` and `VirtualConsole`) to support writing binary data. Instead of `TextReader`/`TextWriter` instances, the streams are now exposed as `StreamReader`/`StreamWriter` which provide the `BaseStream` property that allows raw access. Existing usages inside commands should remain the same because `StreamReader`/`StreamWriter` are compatible with their base classes `TextReader`/`TextWriter`, but if you were using `VirtualConsole` in tests, you may have to update it to the new API. Refer to the readme for more info.
 - Changed argument binding behavior so that an error is produced if the user provides an argument that doesn't match with any parameter or option. This is done in order to improve user experience, as otherwise the user may make a typo without knowing that their input wasn't taken into account.

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

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
@@ -9,14 +9,14 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Basic.Reference.Assemblies" Version="1.2.4" />
-    <PackageReference Include="GitHubActionsTestLogger" Version="1.4.1" PrivateAssets="all" />
-    <PackageReference Include="FluentAssertions" Version="6.6.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.1.0" />
-    <PackageReference Include="xunit" Version="2.4.1" />
+    <PackageReference Include="Basic.Reference.Assemblies.Net70" Version="1.4.2" />
+    <PackageReference Include="GitHubActionsTestLogger" Version="2.2.0" PrivateAssets="all" />
+    <PackageReference Include="FluentAssertions" Version="6.11.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.6.0" />
+    <PackageReference Include="xunit" Version="2.4.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" PrivateAssets="all" />
-    <PackageReference Include="coverlet.collector" Version="3.1.2" PrivateAssets="all" />
+    <PackageReference Include="coverlet.collector" Version="3.2.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Analyzers.Tests/CommandMustBeAnnotatedAnalyzerSpecs.cs

@@ -13,11 +13,13 @@ public class CommandMustBeAnnotatedAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            public class MyCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -28,12 +30,14 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public abstract class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public abstract class MyCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -44,11 +48,13 @@ public abstract class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public abstract class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            public abstract class MyCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -59,11 +65,13 @@ public abstract class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class Foo
-{
-    public int Bar { get; set; } = 5;
-}";
+        const string code =
+            """
+            public class Foo
+            {
+                public int Bar { get; init; } = 5;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/CommandMustImplementInterfaceAnalyzerSpecs.cs

@@ -13,12 +13,14 @@ public class CommandMustImplementInterfaceAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -29,12 +31,14 @@ public class MyCommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -45,11 +49,13 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class Foo
-{
-    public int Bar { get; set; } = 5;
-}";
+        const string code =
+            """
+            public class Foo
+            {
+                public int Bar { get; init; } = 5;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustBeInsideCommandAnalyzerSpecs.cs

@@ -13,12 +13,14 @@ public class OptionMustBeInsideCommandAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyClass
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
-}";
+        const string code =
+            """
+            public class MyClass
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -29,15 +31,17 @@ public class MyClass
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -48,12 +52,14 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public abstract class MyCommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
-}";
+        const string code =
+            """
+            public abstract class MyCommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -64,14 +70,16 @@ public abstract class MyCommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustBeRequiredIfPropertyRequiredAnalyzerSpecs.cs

@@ -0,0 +1,114 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+public class OptionMustBeRequiredIfPropertyRequiredAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new OptionMustBeRequiredIfPropertyRequiredAnalyzer();
+
+    [Fact]
+    public void Analyzer_reports_an_error_if_a_non_required_option_is_bound_to_a_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f', IsRequired = false)]
+                public required string Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_required_option_is_bound_to_a_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public required string Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_non_required_option_is_bound_to_a_non_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f', IsRequired = false)]
+                public string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_required_option_is_bound_to_a_non_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public required string Foo { get; init; }
+
+                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 required string Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+}

CliFx.Analyzers.Tests/OptionMustHaveNameOrShortNameAnalyzerSpecs.cs

@@ -13,15 +13,17 @@ public class OptionMustHaveNameOrShortNameAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(null)]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption(null)]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -32,15 +34,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -51,15 +55,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('f')]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -70,14 +76,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustHaveUniqueNameAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class OptionMustHaveUniqueNameAnalyzerSpecs
     {
         // 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;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            
+                [CommandOption("foo")]
+                public string? Bar { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // 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;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            
+                [CommandOption("bar")]
+                public string? Bar { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,15 +61,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('f')]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -76,14 +82,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustHaveUniqueShortNameAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class OptionMustHaveUniqueShortNameAnalyzerSpecs
     {
         // 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;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+            
+                [CommandOption('f')]
+                public string? Bar { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // 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;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+            
+                [CommandOption('b')]
+                public string? Bar { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,18 +61,20 @@ public class MyCommand : ICommand
     {
         // 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;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+            
+                [CommandOption('F')]
+                public string? Bar { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -79,15 +85,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -98,14 +106,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustHaveValidConverterAnalyzerSpecs.cs

@@ -13,20 +13,22 @@ public class OptionMustHaveValidConverterAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter
-{
-    public string Convert(string rawValue) => rawValue;
-}
+        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; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo", Converter = typeof(MyConverter))]
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -37,20 +39,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<int>
-{
-    public override int Convert(string rawValue) => 42;
-}
+        const string code =
+            """
+            public class MyConverter : BindingConverter<int>
+            {
+                public override int Convert(string? rawValue) => 42;
+            }
 
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"", Converter = typeof(MyConverter))]
-    public string Foo { get; set; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo", Converter = typeof(MyConverter))]
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -61,20 +65,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<string>
-{
-    public override string Convert(string rawValue) => rawValue;
-}
+        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; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo", Converter = typeof(MyConverter))]
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -85,20 +91,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<int>
-{
-    public override int Convert(string rawValue) => 42;
-}
+        const string code =
+            """
+            public class MyConverter : BindingConverter<int>
+            {
+                public override int Convert(string? rawValue) => 42;
+            }
 
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"", Converter = typeof(MyConverter))]
-    public int? Foo { get; set; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo", Converter = typeof(MyConverter))]
+                public int? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -109,20 +117,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<string>
-{
-    public override string Convert(string rawValue) => rawValue;
-}
+        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 IReadOnlyList<string> Foo { get; set; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo", Converter = typeof(MyConverter))]
+                public IReadOnlyList<string>? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -133,15 +143,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -152,14 +164,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustHaveValidNameAnalyzerSpecs.cs

@@ -13,15 +13,17 @@ public class OptionMustHaveValidNameAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""f"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("f")]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -32,15 +34,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""1foo"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("1foo")]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -51,15 +55,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -70,15 +76,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('f')]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -89,14 +97,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustHaveValidShortNameAnalyzerSpecs.cs

@@ -13,15 +13,17 @@ public class OptionMustHaveValidShortNameAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('1')]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('1')]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -32,15 +34,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption('f')]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -51,15 +55,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -70,14 +76,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/OptionMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -13,20 +13,22 @@ public class OptionMustHaveValidValidatorsAnalyzerSpecs
     {
         // 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;
-}";
+        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; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -37,20 +39,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyValidator : BindingValidator<int>
-{
-    public override BindingValidationError Validate(int value) => Ok();
-}
-
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"", Validators = new[] {typeof(MyValidator)})]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            public class MyValidator : BindingValidator<int>
+            {
+                public override BindingValidationError Validate(int value) => Ok();
+            }
+            
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo", Validators = new[] {typeof(MyValidator)})]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -61,20 +65,22 @@ public class MyCommand : ICommand
     {
         // 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;
-}";
+        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; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -85,15 +91,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -104,14 +112,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
+            
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustBeInsideCommandAnalyzerSpecs.cs

@@ -13,12 +13,14 @@ public class ParameterMustBeInsideCommandAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyClass
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
-}";
+        const string code =
+            """
+            public class MyClass
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -29,15 +31,17 @@ public class MyClass
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -48,12 +52,14 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public abstract class MyCommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
-}";
+        const string code =
+            """
+            public abstract class MyCommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -64,14 +70,16 @@ public abstract class MyCommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustBeLastIfNonRequiredAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class ParameterMustBeLastIfNonRequiredAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Name = ""foo"", IsRequired = false)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, IsRequired = false)]
+                public string? Foo { get; init; }
 
-    [CommandParameter(1, Name = ""bar"")]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Name = ""foo"")]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1, Name = ""bar"", IsRequired = false)]
-    public string Bar { get; set; }
+                [CommandParameter(1, IsRequired = false)]
+                public string? Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,18 +61,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Name = ""foo"")]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1, Name = ""bar"", IsRequired = true)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -79,14 +85,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustBeLastIfNonScalarAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class ParameterMustBeLastIfNonScalarAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string[] Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string[] Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string[] Bar { get; set; }
+                [CommandParameter(1)]
+                public required string[] Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,18 +61,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -79,14 +85,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustBeRequiredIfPropertyRequiredAnalyzerSpecs.cs

@@ -0,0 +1,114 @@
+using CliFx.Analyzers.Tests.Utils;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Xunit;
+
+namespace CliFx.Analyzers.Tests;
+
+public class ParameterMustBeRequiredIfPropertyRequiredAnalyzerSpecs
+{
+    private static DiagnosticAnalyzer Analyzer { get; } = new ParameterMustBeRequiredIfPropertyRequiredAnalyzer();
+
+    [Fact]
+    public void Analyzer_reports_an_error_if_a_non_required_parameter_is_bound_to_a_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, IsRequired = false)]
+                public required string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().ProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_required_parameter_is_bound_to_a_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_non_required_parameter_is_bound_to_a_non_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, IsRequired = false)]
+                public string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+
+    [Fact]
+    public void Analyzer_does_not_report_an_error_if_a_required_parameter_is_bound_to_a_non_required_property()
+    {
+        // Arrange
+        // language=cs
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                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 required string Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
+
+        // Act & assert
+        Analyzer.Should().NotProduceDiagnostics(code);
+    }
+}

CliFx.Analyzers.Tests/ParameterMustBeSingleIfNonRequiredAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class ParameterMustBeSingleIfNonRequiredAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, IsRequired = false)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, IsRequired = false)]
+                public string? Foo { get; init; }
 
-    [CommandParameter(1, IsRequired = false)]
-    public string Bar { get; set; }
+                [CommandParameter(1, IsRequired = false)]
+                public string? Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1, IsRequired = false)]
-    public string Bar { get; set; }
+                [CommandParameter(1, IsRequired = false)]
+                public string? Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,18 +61,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1, IsRequired = true)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -79,14 +85,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustBeSingleIfNonScalarAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class ParameterMustBeSingleIfNonScalarAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string[] Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string[] Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string[] Bar { get; set; }
+                [CommandParameter(1)]
+                public required string[] Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string[] Bar { get; set; }
+                [CommandParameter(1)]
+                public required string[] Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,18 +61,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -79,14 +85,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustHaveUniqueNameAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class ParameterMustHaveUniqueNameAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Name = ""foo"")]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Name = "foo")]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1, Name = ""foo"")]
-    public string Bar { get; set; }
+                [CommandParameter(1, Name = "foo")]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Name = ""foo"")]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Name = "foo")]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1, Name = ""bar"")]
-    public string Bar { get; set; }
+                [CommandParameter(1, Name = "bar")]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,14 +61,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustHaveUniqueOrderAnalyzerSpecs.cs

@@ -13,18 +13,20 @@ public class ParameterMustHaveUniqueOrderAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(0)]
-    public string Bar { get; set; }
+                [CommandParameter(0)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -35,18 +37,20 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -57,14 +61,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustHaveValidConverterAnalyzerSpecs.cs

@@ -13,20 +13,22 @@ public class ParameterMustHaveValidConverterAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter
-{
-    public string Convert(string rawValue) => rawValue;
-}
+        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; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Converter = typeof(MyConverter))]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -37,20 +39,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<int>
-{
-    public override int Convert(string rawValue) => 42;
-}
+        const string code =
+            """
+            public class MyConverter : BindingConverter<int>
+            {
+                public override int Convert(string? rawValue) => 42;
+            }
 
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Converter = typeof(MyConverter))]
-    public string Foo { get; set; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Converter = typeof(MyConverter))]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
 
         // Act & assert
@@ -62,20 +66,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<string>
-{
-    public override string Convert(string rawValue) => rawValue;
-}
+        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; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Converter = typeof(MyConverter))]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -86,20 +92,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<int>
-{
-    public override int Convert(string rawValue) => 42;
-}
+        const string code =
+            """
+            public class MyConverter : BindingConverter<int>
+            {
+                public override int Convert(string? rawValue) => 42;
+            }
 
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandOption(""foo"", Converter = typeof(MyConverter))]
-    public int? Foo { get; set; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandOption("foo", Converter = typeof(MyConverter))]
+                public int? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -110,20 +118,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyConverter : BindingConverter<string>
-{
-    public override string Convert(string rawValue) => rawValue;
-}
+        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 IReadOnlyList<string> Foo { get; set; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Converter = typeof(MyConverter))]
+                public required IReadOnlyList<string> Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -134,15 +144,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -153,14 +165,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/ParameterMustHaveValidValidatorsAnalyzerSpecs.cs

@@ -13,20 +13,22 @@ public class ParameterMustHaveValidValidatorsAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyValidator
-{
-    public void Validate(string value) {}
-}
+        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; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -37,20 +39,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyValidator : BindingValidator<int>
-{
-    public override BindingValidationError Validate(int value) => Ok();
-}
+        const string code =
+            """
+            public class MyValidator : BindingValidator<int>
+            {
+                public override BindingValidationError Validate(int value) => Ok();
+            }
 
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
-    public string Foo { get; set; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().ProduceDiagnostics(code);
@@ -61,20 +65,22 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-public class MyValidator : BindingValidator<string>
-{
-    public override BindingValidationError Validate(string value) => Ok();
-}
+        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; }
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0, Validators = new[] {typeof(MyValidator)})]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -85,15 +91,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);
@@ -104,14 +112,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public string Foo { get; set; }
+        const string code =
+            """
+            [Command]
+            public class MyCommand : ICommand
+            {
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """;
 
         // Act & assert
         Analyzer.Should().NotProduceDiagnostics(code);

CliFx.Analyzers.Tests/SystemConsoleShouldBeAvoidedAnalyzerSpecs.cs

@@ -13,16 +13,18 @@ public class SystemConsoleShouldBeAvoidedAnalyzerSpecs
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        Console.WriteLine(""Hello world"");
-        return default;
-    }
-}";
+        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);
@@ -33,16 +35,19 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        Console.ForegroundColor = ConsoleColor.Black;
-        return default;
-    }
-}";
+        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);
     }
@@ -52,16 +57,18 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        Console.Error.WriteLine(""Hello world"");
-        return default;
-    }
-}";
+        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);
@@ -72,16 +79,18 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""Hello world"");
-        return default;
-    }
-}";
+        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);
@@ -92,14 +101,16 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public void SomeOtherMethod() => Console.WriteLine(""Test"");
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}";
+        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);
@@ -110,15 +121,17 @@ public class MyCommand : ICommand
     {
         // Arrange
         // language=cs
-        const string code = @"
-[Command]
-public class MyCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        return default;
-    }
-}";
+        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

@@ -58,7 +58,7 @@ internal class AnalyzerAssertions : ReferenceTypeAssertions<DiagnosticAnalyzer,
         var compilation = CSharpCompilation.Create(
             "CliFxTests_DynamicAssembly_" + Guid.NewGuid(),
             new[] { ast },
-            ReferenceAssemblies.Net50
+            Net70.References.All
                 .Append(MetadataReference.CreateFromFile(typeof(ICommand).Assembly.Location)),
             // DLL to avoid having to define the Main() method
             new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
@@ -72,9 +72,10 @@ internal class AnalyzerAssertions : ReferenceTypeAssertions<DiagnosticAnalyzer,
         if (compilationErrors.Any())
         {
             throw new InvalidOperationException(
-                "Failed to compile code." +
-                Environment.NewLine +
-                string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))
+                $"""
+                Failed to compile code.
+                {string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))}
+                """
             );
         }
 

CliFx.Analyzers/CliFx.Analyzers.csproj

@@ -3,14 +3,24 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
-    <Nullable>annotations</Nullable>
+    <GenerateDependencyFile>true</GenerateDependencyFile>
+    <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
     <NoWarn>$(NoWarn);RS1025;RS1026</NoWarn>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <!--
+      Because this project only has a single target framework, the condition in
+      Directory.Build.props does not appear to work. This is a workaround for that.
+    -->
+    <Nullable>annotations</Nullable>
+  </PropertyGroup>
+
   <ItemGroup>
-    <!-- Keep this dependency as low as possible since we can't bundle it -->
-    <!-- https://github.com/Tyrrrz/CliFx/issues/127 -->
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.8.0" PrivateAssets="all" />
+    <!-- Make sure to target the lowest possible version of the compiler for wider support -->
+    <PackageReference Include="Microsoft.CodeAnalysis" Version="3.0.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.0.0" PrivateAssets="all" />
+    <PackageReference Include="PolyShim" Version="1.2.0" PrivateAssets="all" />
   </ItemGroup>
 
 </Project>

CliFx.Analyzers/ObjectModel/CommandOptionSymbol.cs

@@ -13,6 +13,8 @@ internal partial class CommandOptionSymbol : ICommandMemberSymbol
 
     public char? ShortName { get; }
 
+    public bool? IsRequired { get; }
+
     public ITypeSymbol? ConverterType { get; }
 
     public IReadOnlyList<ITypeSymbol> ValidatorTypes { get; }
@@ -21,12 +23,14 @@ internal partial class CommandOptionSymbol : ICommandMemberSymbol
         IPropertySymbol property,
         string? name,
         char? shortName,
+        bool? isRequired,
         ITypeSymbol? converterType,
         IReadOnlyList<ITypeSymbol> validatorTypes)
     {
         Property = property;
         Name = name;
         ShortName = shortName;
+        IsRequired = isRequired;
         ConverterType = converterType;
         ValidatorTypes = validatorTypes;
     }
@@ -56,6 +60,12 @@ internal partial class CommandOptionSymbol
             .Select(a => a.Value)
             .FirstOrDefault() as char?;
 
+        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")
@@ -71,7 +81,7 @@ internal partial class CommandOptionSymbol
             .Cast<ITypeSymbol>()
             .ToArray();
 
-        return new CommandOptionSymbol(property, name, shortName, converter, validators);
+        return new CommandOptionSymbol(property, name, shortName, isRequired, converter, validators);
     }
 
     public static bool IsOptionProperty(IPropertySymbol property) =>

CliFx.Analyzers/OptionMustBeRequiredIfPropertyRequiredAnalyzer.cs

@@ -0,0 +1,49 @@
+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 OptionMustBeRequiredIfPropertyRequiredAnalyzer : AnalyzerBase
+{
+    public OptionMustBeRequiredIfPropertyRequiredAnalyzer()
+        : base(
+            "Options bound to required properties cannot be marked as non-required",
+            "This option cannot be marked as non-required because it's bound to a required property.")
+    {
+    }
+
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        if (!property.IsRequired())
+            return;
+
+        var option = CommandOptionSymbol.TryResolve(property);
+        if (option is null)
+            return;
+
+        if (option.IsRequired != false)
+            return;
+
+        context.ReportDiagnostic(
+            CreateDiagnostic(
+                propertyDeclaration.Identifier.GetLocation()
+            )
+        );
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/OptionMustHaveUniqueNameAnalyzer.cs

@@ -39,7 +39,7 @@ public class OptionMustHaveUniqueNameAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/OptionMustHaveUniqueShortNameAnalyzer.cs

@@ -38,7 +38,7 @@ public class OptionMustHaveUniqueShortNameAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/ParameterMustBeLastIfNonRequiredAnalyzer.cs

@@ -37,7 +37,7 @@ public class ParameterMustBeLastIfNonRequiredAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/ParameterMustBeLastIfNonScalarAnalyzer.cs

@@ -37,7 +37,7 @@ public class ParameterMustBeLastIfNonScalarAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/ParameterMustBeRequiredIfPropertyRequiredAnalyzer.cs

@@ -0,0 +1,49 @@
+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 ParameterMustBeRequiredIfPropertyRequiredAnalyzer : AnalyzerBase
+{
+    public ParameterMustBeRequiredIfPropertyRequiredAnalyzer()
+        : base(
+            "Parameters bound to required properties cannot be marked as non-required",
+            "This parameter cannot be marked as non-required because it's bound to a required property.")
+    {
+    }
+
+    private void Analyze(
+        SyntaxNodeAnalysisContext context,
+        PropertyDeclarationSyntax propertyDeclaration,
+        IPropertySymbol property)
+    {
+        if (property.ContainingType is null)
+            return;
+
+        if (!property.IsRequired())
+            return;
+
+        var parameter = CommandParameterSymbol.TryResolve(property);
+        if (parameter is null)
+            return;
+
+        if (parameter.IsRequired != false)
+            return;
+
+        context.ReportDiagnostic(
+            CreateDiagnostic(
+                propertyDeclaration.Identifier.GetLocation()
+            )
+        );
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+        context.HandlePropertyDeclaration(Analyze);
+    }
+}

CliFx.Analyzers/ParameterMustBeSingleIfNonRequiredAnalyzer.cs

@@ -37,7 +37,7 @@ public class ParameterMustBeSingleIfNonRequiredAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/ParameterMustBeSingleIfNonScalarAnalyzer.cs

@@ -37,7 +37,7 @@ public class ParameterMustBeSingleIfNonScalarAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/ParameterMustHaveUniqueNameAnalyzer.cs

@@ -39,7 +39,7 @@ public class ParameterMustHaveUniqueNameAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/ParameterMustHaveUniqueOrderAnalyzer.cs

@@ -35,7 +35,7 @@ public class ParameterMustHaveUniqueOrderAnalyzer : AnalyzerBase
             .ContainingType
             .GetMembers()
             .OfType<IPropertySymbol>()
-            .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+            .Where(m => !m.Equals(property))
             .ToArray();
 
         foreach (var otherProperty in otherProperties)

CliFx.Analyzers/Utils/Extensions/RoslynExtensions.cs

@@ -34,6 +34,17 @@ internal static class RoslynExtensions
         .FirstOrDefault(i => i.ConstructedFrom.SpecialType == SpecialType.System_Collections_Generic_IEnumerable_T)?
         .TypeArguments[0];
 
+    // Detect if the property is required through roundabout means so as to not have to take dependency
+    // on higher versions of the C# compiler.
+    public static bool IsRequired(this IPropertySymbol property) => property
+        // Can't rely on the RequiredMemberAttribute because it's generated by the compiler, not added by the user,
+        // so we have to check for the presence of the `required` modifier in the syntax tree instead.
+        .DeclaringSyntaxReferences
+        .Select(r => r.GetSyntax())
+        .OfType<PropertyDeclarationSyntax>()
+        .SelectMany(p => p.Modifiers)
+        .Any(m => m.IsKind((SyntaxKind)8447));
+
     public static bool IsAssignable(this Compilation compilation, ITypeSymbol source, ITypeSymbol destination) =>
         compilation.ClassifyConversion(source, destination).Exists;
 

CliFx.Analyzers/Utils/Extensions/StringExtensions.cs

@@ -10,7 +10,7 @@ internal static class StringExtensions
         StringComparison comparison = StringComparison.Ordinal)
     {
         while (str.EndsWith(sub, comparison))
-            str = str.Substring(0, str.Length - sub.Length);
+            str = str[..^sub.Length];
 
         return str;
     }

CliFx.Benchmarks/CliFx.Benchmarks.csproj

@@ -2,16 +2,16 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.13.1" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.13.5" />
     <PackageReference Include="clipr" Version="1.6.1" />
-    <PackageReference Include="Cocona" Version="2.0.3" />
-    <PackageReference Include="CommandLineParser" Version="2.8.0" />
-    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="4.0.1" />
-    <PackageReference Include="PowerArgs" Version="3.6.0" />
+    <PackageReference Include="Cocona" Version="2.2.0" />
+    <PackageReference Include="CommandLineParser" Version="2.9.1" />
+    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="4.0.2" />
+    <PackageReference Include="PowerArgs" Version="4.0.2" />
     <PackageReference Include="System.CommandLine" Version="2.0.0-beta1.20574.7" />
   </ItemGroup>
 

CliFx.Demo/CliFx.Demo.csproj

@@ -2,12 +2,11 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0" />
-    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="7.0.0" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Demo/Commands/BookAddCommand.cs

@@ -14,10 +14,10 @@ public partial class BookAddCommand : ICommand
     private readonly LibraryProvider _libraryProvider;
 
     [CommandParameter(0, Name = "title", Description = "Book title.")]
-    public string Title { get; init; } = "";
+    public required string Title { get; init; }
 
-    [CommandOption("author", 'a', IsRequired = true, Description = "Book author.")]
-    public string Author { get; init; } = "";
+    [CommandOption("author", 'a', Description = "Book author.")]
+    public required string Author { get; init; }
 
     [CommandOption("published", 'p', Description = "Book publish date.")]
     public DateTimeOffset Published { get; init; } = CreateRandomDate();

CliFx.Demo/Commands/BookCommand.cs

@@ -13,7 +13,7 @@ public class BookCommand : ICommand
     private readonly LibraryProvider _libraryProvider;
 
     [CommandParameter(0, Name = "title", Description = "Title of the book to retrieve.")]
-    public string Title { get; init; } = "";
+    public required string Title { get; init; }
 
     public BookCommand(LibraryProvider libraryProvider)
     {

CliFx.Demo/Commands/BookRemoveCommand.cs

@@ -12,7 +12,7 @@ public class BookRemoveCommand : ICommand
     private readonly LibraryProvider _libraryProvider;
 
     [CommandParameter(0, Name = "title", Description = "Title of the book to remove.")]
-    public string Title { get; init; } = "";
+    public required string Title { get; init; }
 
     public BookRemoveCommand(LibraryProvider libraryProvider)
     {

CliFx.Demo/Domain/Book.cs

@@ -2,21 +2,4 @@
 
 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;
-    }
-}
+public record Book(string Title, string Author, DateTimeOffset Published, Isbn Isbn);

CliFx.Demo/Domain/Isbn.cs

@@ -2,32 +2,13 @@
 
 namespace CliFx.Demo.Domain;
 
-public partial class Isbn
+public partial record Isbn(int EanPrefix, int RegistrationGroup, int Registrant, int Publication, int CheckDigit)
 {
-    public int EanPrefix { get; }
-
-    public int RegistrationGroup { get; }
-
-    public int Registrant { get; }
-
-    public int Publication { get; }
-
-    public int CheckDigit { get; }
-
-    public Isbn(int eanPrefix, int registrationGroup, int registrant, int publication, int checkDigit)
-    {
-        EanPrefix = eanPrefix;
-        RegistrationGroup = registrationGroup;
-        Registrant = registrant;
-        Publication = publication;
-        CheckDigit = checkDigit;
-    }
-
     public override string ToString() =>
         $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
 }
 
-public partial class Isbn
+public partial record Isbn
 {
     public static Isbn Parse(string value, IFormatProvider formatProvider)
     {

CliFx.Demo/Domain/Library.cs

@@ -4,15 +4,8 @@ using System.Linq;
 
 namespace CliFx.Demo.Domain;
 
-public partial class Library
+public partial record Library(IReadOnlyList<Book> Books)
 {
-    public IReadOnlyList<Book> Books { get; }
-
-    public Library(IReadOnlyList<Book> books)
-    {
-        Books = books;
-    }
-
     public Library WithBook(Book book)
     {
         var books = Books.ToList();
@@ -29,7 +22,7 @@ public partial class Library
     }
 }
 
-public partial class Library
+public partial record Library
 {
     public static Library Empty { get; } = new(Array.Empty<Book>());
 }

CliFx.Demo/Domain/LibraryProvider.cs

@@ -1,6 +1,6 @@
 using System.IO;
 using System.Linq;
-using Newtonsoft.Json;
+using System.Text.Json;
 
 namespace CliFx.Demo.Domain;
 
@@ -10,7 +10,7 @@ public class LibraryProvider
 
     private void StoreLibrary(Library library)
     {
-        var data = JsonConvert.SerializeObject(library);
+        var data = JsonSerializer.Serialize(library);
         File.WriteAllText(StorageFilePath, data);
     }
 
@@ -21,7 +21,7 @@ public class LibraryProvider
 
         var data = File.ReadAllText(StorageFilePath);
 
-        return JsonConvert.DeserializeObject<Library>(data) ?? Library.Empty;
+        return JsonSerializer.Deserialize<Library>(data) ?? Library.Empty;
     }
 
     public Book? TryGetBook(string title) => GetLibrary().Books.FirstOrDefault(b => b.Title == title);

CliFx.Demo/Program.cs

@@ -1,25 +1,21 @@
 using CliFx;
-using CliFx.Demo.Commands;
 using CliFx.Demo.Domain;
 using Microsoft.Extensions.DependencyInjection;
 
-// We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
-var services = new ServiceCollection();
-
-// Register services
-services.AddSingleton<LibraryProvider>();
-
-// Register commands
-services.AddTransient<BookCommand>();
-services.AddTransient<BookAddCommand>();
-services.AddTransient<BookRemoveCommand>();
-services.AddTransient<BookListCommand>();
-
-var serviceProvider = services.BuildServiceProvider();
-
 return await new CliApplicationBuilder()
     .SetDescription("Demo application showcasing CliFx features.")
     .AddCommandsFromThisAssembly()
-    .UseTypeActivator(serviceProvider.GetRequiredService)
+    .UseTypeActivator(commandTypes =>
+    {
+        // We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
+        var services = new ServiceCollection();
+        services.AddSingleton<LibraryProvider>();
+
+        // Register all commands as transient services
+        foreach (var commandType in commandTypes)
+            services.AddTransient(commandType);
+
+        return services.BuildServiceProvider();
+    })
     .Build()
     .RunAsync();

CliFx.Demo/Readme.md

@@ -1,5 +1,5 @@
 # CliFx Demo Project
 
-Sample command line interface for managing a library of books.
+Sample command-line interface for managing a library of books.
 
-This demo project showcases basic CliFx functionality such as command routing, argument parsing, autogenerated help text.
+This demo project showcases basic CliFx functionality such as command routing, argument parsing, and autogenerated help text.

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

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>

CliFx.Tests.Dummy/Commands/CancellationTestCommand.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Infrastructure;
+
+namespace CliFx.Tests.Dummy.Commands;
+
+[Command("cancel-test")]
+public class CancellationTestCommand : ICommand
+{
+    public async ValueTask ExecuteAsync(IConsole console)
+    {
+        try
+        {
+            console.Output.WriteLine("Started.");
+
+            await Task.Delay(
+                TimeSpan.FromSeconds(3),
+                console.RegisterCancellationHandler()
+            );
+
+            console.Output.WriteLine("Completed.");
+        }
+        catch (OperationCanceledException)
+        {
+            console.Output.WriteLine("Cancelled.");
+            throw;
+        }
+    }
+}

CliFx.Tests.Dummy/Commands/EnvironmentTestCommand.cs

@@ -8,7 +8,7 @@ namespace CliFx.Tests.Dummy.Commands;
 public class EnvironmentTestCommand : ICommand
 {
     [CommandOption("target", EnvironmentVariable = "ENV_TARGET")]
-    public string GreetingTarget { get; set; } = "World";
+    public string GreetingTarget { get; init; } = "World";
 
     public ValueTask ExecuteAsync(IConsole console)
     {

CliFx.Tests.Dummy/Program.cs

@@ -3,12 +3,11 @@ using System.Reflection;
 using System.Threading.Tasks;
 
 namespace CliFx.Tests.Dummy;
-// This dummy application is used in tests for scenarios
-// that require an external process to properly verify.
 
+// This dummy application is used in tests for scenarios that require an external process to properly verify
 public static partial class Program
 {
-    public static Assembly Assembly { get; } = typeof(Program).Assembly;
+    public static Assembly Assembly { get; } = Assembly.GetExecutingAssembly();
 
     public static string Location { get; } = Assembly.Location;
 }

CliFx.Tests/ApplicationSpecs.cs

@@ -16,7 +16,7 @@ public class ApplicationSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Application_can_be_created_with_minimal_configuration()
+    public async Task I_can_create_an_application_with_the_default_configuration()
     {
         // Act
         var app = new CliApplicationBuilder()
@@ -34,7 +34,7 @@ public class ApplicationSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Application_can_be_created_with_a_fully_customized_configuration()
+    public async Task I_can_create_an_application_with_a_custom_configuration()
     {
         // Act
         var app = new CliApplicationBuilder()
@@ -63,7 +63,7 @@ public class ApplicationSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Application_configuration_fails_if_an_invalid_command_is_registered()
+    public async Task I_cannot_add_an_invalid_command_to_the_application()
     {
         // Act
         var app = new CliApplicationBuilder()
@@ -76,10 +76,10 @@ public class ApplicationSpecs : SpecsBase
             new Dictionary<string, string>()
         );
 
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Should().Contain("not a valid command");
     }
 }

CliFx.Tests/CancellationSpecs.cs

@@ -1,7 +1,11 @@
 using System;
 using System.Collections.Generic;
+using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
+using CliWrap;
 using FluentAssertions;
 using Xunit;
 using Xunit.Abstractions;
@@ -15,52 +19,103 @@ public class CancellationSpecs : SpecsBase
     {
     }
 
+    [Fact(Timeout = 15000)]
+    public async Task I_can_configure_the_command_to_listen_to_the_interrupt_signal()
+    {
+        // Arrange
+        using var cts = new CancellationTokenSource();
+
+        // We need to send the cancellation request right after the process has registered
+        // a handler for the interrupt signal, otherwise the default handler will trigger
+        // and just kill the process.
+        void HandleStdOut(string line)
+        {
+            if (string.Equals(line, "Started.", StringComparison.OrdinalIgnoreCase))
+                cts.CancelAfter(TimeSpan.FromSeconds(0.2));
+        }
+
+        var stdOutBuffer = new StringBuilder();
+
+        var pipeTarget = PipeTarget.Merge(
+            PipeTarget.ToDelegate(HandleStdOut),
+            PipeTarget.ToStringBuilder(stdOutBuffer)
+        );
+
+        var command = Cli.Wrap("dotnet")
+            .WithArguments(a => a
+                .Add(Dummy.Program.Location)
+                .Add("cancel-test")
+            ) | pipeTarget;
+
+        // Act & assert
+        await Assert.ThrowsAnyAsync<OperationCanceledException>(async () =>
+            await command.ExecuteAsync(
+                // Forceful cancellation (not required because we have a timeout)
+                CancellationToken.None,
+                // Graceful cancellation
+                cts.Token
+            )
+        );
+
+        stdOutBuffer.ToString().Trim().Should().ConsistOfLines(
+            "Started.",
+            "Cancelled."
+        );
+    }
+
     [Fact]
-    public async Task Command_can_register_to_receive_a_cancellation_signal_from_the_console()
+    public async Task I_can_configure_the_command_to_listen_to_the_interrupt_signal_when_running_in_isolation()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public async ValueTask ExecuteAsync(IConsole console)
-    {
-        try
-        {
-            await Task.Delay(
-                TimeSpan.FromSeconds(3),
-                console.RegisterCancellationHandler()
-            );
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public async ValueTask ExecuteAsync(IConsole console)
+                {
+                    try
+                    {
+                        console.Output.WriteLine("Started.");
 
-            console.Output.WriteLine(""Completed successfully"");
-        }
-        catch (OperationCanceledException)
-        {
-            console.Output.WriteLine(""Cancelled"");
-            throw;
-        }
-    }
-}");
+                        await Task.Delay(
+                            TimeSpan.FromSeconds(3),
+                            console.RegisterCancellationHandler()
+                        );
+
+                        console.Output.WriteLine("Completed.");
+                    }
+                    catch (OperationCanceledException)
+                    {
+                        console.Output.WriteLine("Cancelled.");
+                        throw;
+                    }
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
             .UseConsole(FakeConsole)
             .Build();
 
-        // Act
         FakeConsole.RequestCancellation(TimeSpan.FromSeconds(0.2));
 
+        // Act
         var exitCode = await application.RunAsync(
             Array.Empty<string>(),
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().NotBe(0);
-        stdOut.Trim().Should().Be("Cancelled");
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().ConsistOfLines(
+            "Started.",
+            "Cancelled."
+        );
     }
 }

CliFx.Tests/CliFx.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
@@ -9,15 +9,16 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Basic.Reference.Assemblies" Version="1.2.4" />
-    <PackageReference Include="CliWrap" Version="3.4.4" />
-    <PackageReference Include="FluentAssertions" Version="6.6.0" />
-    <PackageReference Include="GitHubActionsTestLogger" Version="1.4.1" PrivateAssets="all" />
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.1.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
-    <PackageReference Include="xunit" Version="2.4.1" />
+    <PackageReference Include="Basic.Reference.Assemblies.Net70" Version="1.4.2" />
+    <PackageReference Include="CliWrap" Version="3.6.1" />
+    <PackageReference Include="FluentAssertions" Version="6.11.0" />
+    <PackageReference Include="GitHubActionsTestLogger" Version="2.2.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.6.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="7.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
+    <PackageReference Include="xunit" Version="2.4.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" PrivateAssets="all" />
-    <PackageReference Include="coverlet.collector" Version="3.1.2" PrivateAssets="all" />
+    <PackageReference Include="coverlet.collector" Version="3.2.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>
@@ -25,12 +26,4 @@
     <ProjectReference Include="..\CliFx\CliFx.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <None Include="../CliFx.Tests.Dummy/bin/$(Configuration)/$(TargetFramework)/CliFx.Tests.Dummy.runtimeconfig.json">
-      <Link>CliFx.Tests.Dummy.runtimeconfig.json</Link>
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-      <Visible>false</Visible>
-    </None>
-  </ItemGroup>
-
 </Project>

CliFx.Tests/ConsoleSpecs.cs

@@ -21,11 +21,10 @@ public class ConsoleSpecs : SpecsBase
     {
     }
 
-    [Fact]
-    public async Task Real_console_maps_directly_to_system_console()
+    [Fact(Timeout = 15000)]
+    public async Task I_can_run_the_application_with_the_default_console_implementation_to_interact_with_the_system_console()
     {
-        // Can't verify our own console output, so using an
-        // external process for this test.
+        // Can't verify our own console output, so using an external process for this test
 
         // Arrange
         var command = "Hello world" | Cli.Wrap("dotnet")
@@ -43,30 +42,52 @@ public class ConsoleSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Fake_console_does_not_leak_to_system_console()
+    public void I_can_run_the_application_on_a_system_with_a_custom_console_encoding_and_not_get_corrupted_output()
+    {
+        // Arrange
+        using var buffer = new MemoryStream();
+        using var consoleWriter = new ConsoleWriter(FakeConsole, buffer, Encoding.UTF8);
+
+        // Act
+        consoleWriter.Write("Hello world");
+        consoleWriter.Flush();
+
+        // Assert
+        var outputBytes = buffer.ToArray();
+        outputBytes.Should().NotContain(Encoding.UTF8.GetPreamble());
+
+        var output = consoleWriter.Encoding.GetString(outputBytes);
+        output.Should().Be("Hello world");
+    }
+
+    [Fact]
+    public async Task I_can_run_the_application_with_the_fake_console_implementation_to_isolate_console_interactions()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{   
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.ResetColor();
-        console.ForegroundColor = ConsoleColor.DarkMagenta;
-        console.BackgroundColor = ConsoleColor.DarkMagenta;
-        console.CursorLeft = 42;
-        console.CursorTop = 24;
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.ResetColor();
+                    console.ForegroundColor = ConsoleColor.DarkMagenta;
+                    console.BackgroundColor = ConsoleColor.DarkMagenta;
+                    console.WindowWidth = 100;
+                    console.WindowHeight = 25;
+                    console.CursorLeft = 42;
+                    console.CursorTop = 24;
 
-        console.Output.WriteLine(""Hello "");
-        console.Error.WriteLine(""world!"");
+                    console.Output.WriteLine("Hello ");
+                    console.Error.WriteLine("world!");
 
-        return default;
-    }
-}
-");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -90,6 +111,8 @@ public class Command : ICommand
         Console.BackgroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
 
         // This fails because tests don't spawn a console window
+        //Console.WindowWidth.Should().Be(100);
+        //Console.WindowHeight.Should().Be(25);
         //Console.CursorLeft.Should().NotBe(42);
         //Console.CursorTop.Should().NotBe(24);
 
@@ -99,25 +122,26 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Fake_console_can_be_used_with_an_in_memory_backing_store()
+    public async Task I_can_run_the_application_with_the_fake_console_implementation_and_simulate_stream_interactions()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{   
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        var input = console.Input.ReadToEnd();
-        console.Output.WriteLine(input);
-        console.Error.WriteLine(input);
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    var input = console.Input.ReadToEnd();
+                    console.Output.WriteLine(input);
+                    console.Error.WriteLine(input);
 
-        return default;
-    }
-}
-");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -132,35 +156,37 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Trim().Should().Be("Hello world");
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Trim().Should().Be("Hello world");
     }
 
     [Fact]
-    public async Task Fake_console_can_read_key_presses()
+    public async Task I_can_run_the_application_with_the_fake_console_implementation_and_simulate_key_presses()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{   
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(console.ReadKey().Key);
-        console.Output.WriteLine(console.ReadKey().Key);
-        console.Output.WriteLine(console.ReadKey().Key);
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine(console.ReadKey().Key);
+                    console.Output.WriteLine(console.ReadKey().Key);
+                    console.Output.WriteLine(console.ReadKey().Key);
 
-        return default;
-    }
-}
-");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -177,31 +203,14 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Trim().Should().ConsistOfLines(
             "D0",
             "A",
             "Backspace"
         );
     }
-
-    [Fact]
-    public void Console_does_not_emit_preamble_when_used_with_encoding_that_has_it()
-    {
-        // Arrange
-        using var buffer = new MemoryStream();
-        using var consoleWriter = new ConsoleWriter(FakeConsole, buffer, Encoding.UTF8);
-
-        // Act
-        consoleWriter.Write("Hello world");
-        consoleWriter.Flush();
-
-        var output = consoleWriter.Encoding.GetString(buffer.ToArray());
-
-        // Assert
-        output.Should().Be("Hello world");
-    }
 }

CliFx.Tests/DirectivesSpecs.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using CliFx.Tests.Utils;
@@ -19,69 +18,51 @@ public class DirectivesSpecs : SpecsBase
     {
     }
 
-    [Fact]
-    public async Task Debug_directive_can_be_specified_to_interrupt_execution_until_a_debugger_is_attached()
+    [Fact(Timeout = 15000)]
+    public async Task I_can_use_the_debug_directive_to_make_the_application_wait_for_the_debugger_to_attach()
     {
         // Arrange
-        var stdOutBuffer = new StringBuilder();
+        using var cts = new CancellationTokenSource();
+
+        // We can't actually attach a debugger, but we can ensure that the process is waiting for one
+        void HandleStdOut(string line)
+        {
+            // Kill the process once it writes the output we expect
+            if (line.Contains("Attach the debugger to", StringComparison.OrdinalIgnoreCase))
+                cts.Cancel();
+        }
 
         var command = Cli.Wrap("dotnet")
             .WithArguments(a => a
                 .Add(Dummy.Program.Location)
                 .Add("[debug]")
-            ) | stdOutBuffer;
+            ) | HandleStdOut;
 
-        // Act
+        // Act & assert
         try
         {
-            // This has a timeout just in case the execution hangs forever
-            using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
-
-            var task = command.ExecuteAsync(cts.Token);
-
-            // We can't attach a debugger programmatically, so the application
-            // will hang indefinitely.
-            // To work around it, we will wait until the application writes
-            // something to the standard output and then kill it.
-            while (true)
-            {
-                if (stdOutBuffer.Length > 0)
-                {
-                    cts.Cancel();
-                    break;
-                }
-
-                await Task.Delay(100, cts.Token);
-            }
-
-            await task;
+            await command.ExecuteAsync(cts.Token);
         }
-        catch (OperationCanceledException)
+        catch (OperationCanceledException ex) when (ex.CancellationToken == cts.Token)
         {
-            // This is expected
+            // This means that the process was killed after it wrote the expected output
         }
-
-        var stdOut = stdOutBuffer.ToString();
-
-        // Assert
-        stdOut.Should().Contain("Attach debugger to");
-
-        TestOutput.WriteLine(stdOut);
     }
 
     [Fact]
-    public async Task Preview_directive_can_be_specified_to_print_command_input()
+    public async Task I_can_use_the_preview_directive_to_make_the_application_print_the_parsed_command_input()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command(""cmd"")]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}
-");
+            """
+            [Command("cmd")]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -99,10 +80,10 @@ public class Command : ICommand
             }
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().ContainAllInOrder(
             "cmd", "<param>", "[-a]", "[-b]", "[-c]", "[--option \"foo\"]",
             "ENV_QOP", "=", "\"hello\"",

CliFx.Tests/EnvironmentSpecs.cs

@@ -20,25 +20,31 @@ public class EnvironmentSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Option_can_fall_back_to_an_environment_variable()
+    public async Task I_can_configure_an_option_to_fall_back_to_an_environment_variable_if_the_user_does_not_provide_the_corresponding_argument()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandOption(""foo"", IsRequired = true, EnvironmentVariable = ""ENV_FOO"")]
-    public string Foo { get; set; }
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo", EnvironmentVariable = "ENV_FOO")]
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(Foo);
-        return default;
-    }
-}
-");
+                [CommandOption("bar", EnvironmentVariable = "ENV_BAR")]
+                public string? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine(Foo);
+                    console.Output.WriteLine(Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -47,85 +53,48 @@ public class Command : ICommand
 
         // Act
         var exitCode = await application.RunAsync(
-            Array.Empty<string>(),
+            new[] {"--foo", "42"},
             new Dictionary<string, string>
             {
-                ["ENV_FOO"] = "bar"
+                ["ENV_FOO"] = "100",
+                ["ENV_BAR"] = "200"
             }
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
-        stdOut.Trim().Should().Be("bar");
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().ConsistOfLines(
+            "42",
+            "200"
+        );
     }
 
     [Fact]
-    public async Task Option_does_not_fall_back_to_an_environment_variable_if_a_value_is_provided_through_arguments()
+    public async Task I_can_configure_an_option_bound_to_a_non_scalar_property_to_fall_back_to_an_environment_variable_if_the_user_does_not_provide_the_corresponding_argument()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(Foo);
-        return default;
-    }
-}
-");
-
-        var application = new CliApplicationBuilder()
-            .AddCommand(commandType)
-            .UseConsole(FakeConsole)
-            .Build();
-
-        // Act
-        var exitCode = await application.RunAsync(
-            new[] {"--foo", "baz"},
-            new Dictionary<string, string>
+            """
+            [Command]
+            public class Command : ICommand
             {
-                ["ENV_FOO"] = "bar"
+                [CommandOption("foo", EnvironmentVariable = "ENV_FOO")]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.Output.WriteLine(i);
+
+                    return default;
+                }
             }
+            """
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
-        // Assert
-        exitCode.Should().Be(0);
-        stdOut.Trim().Should().Be("baz");
-    }
-
-    [Fact]
-    public async Task Option_of_non_scalar_type_can_receive_multiple_values_from_an_environment_variable()
-    {
-        // Arrange
-        var commandType = DynamicCommandBuilder.Compile(
-            // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
-    public IReadOnlyList<string> Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        foreach (var i in Foo)
-            console.Output.WriteLine(i);
-
-        return default;
-    }
-}
-");
-
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
             .UseConsole(FakeConsole)
@@ -140,10 +109,10 @@ public class Command : ICommand
             }
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().ConsistOfLines(
             "bar",
             "baz"
@@ -151,25 +120,26 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Option_of_scalar_type_always_receives_a_single_value_from_an_environment_variable()
+    public async Task I_can_configure_an_option_bound_to_a_scalar_property_to_fall_back_to_an_environment_variable_while_ignoring_path_separators()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
-    public string Foo { get; set; }
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo", EnvironmentVariable = "ENV_FOO")]
+                public string? Foo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(Foo);
-        return default;
-    }
-}
-");
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -185,59 +155,15 @@ public class Command : ICommand
             }
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Trim().Should().Be($"bar{Path.PathSeparator}baz");
     }
 
-    [Fact]
-    public async Task Environment_variables_are_matched_case_sensitively()
-    {
-        // Arrange
-        var commandType = DynamicCommandBuilder.Compile(
-            // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandOption(""foo"", EnvironmentVariable = ""ENV_FOO"")]
-    public string Foo { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(Foo);
-        return default;
-    }
-}
-");
-
-        var application = new CliApplicationBuilder()
-            .AddCommand(commandType)
-            .UseConsole(FakeConsole)
-            .Build();
-
-        // Act
-        var exitCode = await application.RunAsync(
-            Array.Empty<string>(),
-            new Dictionary<string, string>
-            {
-                ["ENV_foo"] = "baz",
-                ["ENV_FOO"] = "bar",
-                ["env_FOO"] = "qop"
-            }
-        );
-
-        var stdOut = FakeConsole.ReadOutputString();
-
-        // Assert
-        exitCode.Should().Be(0);
-        stdOut.Trim().Should().Be("bar");
-    }
-
-    [Fact]
-    public async Task Environment_variables_are_extracted_automatically()
+    [Fact(Timeout = 15000)]
+    public async Task I_can_run_the_application_and_it_will_resolve_all_required_environment_variables_automatically()
     {
         // Ensures that the environment variables are properly obtained from
         // System.Environment when they are not provided explicitly to CliApplication.

CliFx.Tests/ErrorReportingSpecs.cs

@@ -17,19 +17,20 @@ public class ErrorReportingSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Command_can_throw_an_exception_which_exits_with_a_stacktrace()
+    public async Task I_can_throw_an_exception_in_a_command_to_report_an_error_with_a_stacktrace()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) =>
-        throw new Exception(""Something went wrong"");
-}
-");
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new Exception("Something went wrong");
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -42,12 +43,13 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().NotBe(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().BeEmpty();
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Should().ContainAllInOrder(
             "System.Exception", "Something went wrong",
             "at", "CliFx."
@@ -55,19 +57,20 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Command_can_throw_an_exception_with_an_inner_exception_which_exits_with_a_stacktrace()
+    public async Task I_can_throw_an_exception_with_an_inner_exception_in_a_command_to_report_an_error_with_a_stacktrace()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) =>
-        throw new Exception(""Something went wrong"", new Exception(""Another exception""));
-}
-");
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new Exception("Something went wrong", new Exception("Another exception"));
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -80,12 +83,13 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().NotBe(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().BeEmpty();
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Should().ContainAllInOrder(
             "System.Exception", "Something went wrong",
             "System.Exception", "Another exception",
@@ -94,19 +98,20 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Command_can_throw_a_special_exception_which_exits_with_specified_code_and_message()
+    public async Task I_can_throw_an_exception_in_a_command_to_report_an_error_and_exit_with_the_specified_code()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) =>
-        throw new CommandException(""Something went wrong"", 69);
-}
-");
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new CommandException("Something went wrong", 69);
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -119,29 +124,31 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().Be(69);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().BeEmpty();
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Trim().Should().Be("Something went wrong");
     }
 
     [Fact]
-    public async Task Command_can_throw_a_special_exception_without_message_which_exits_with_a_stacktrace()
+    public async Task I_can_throw_an_exception_without_a_message_in_a_command_to_report_an_error_with_a_stacktrace()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) =>
-        throw new CommandException("""", 69);
-}
-");
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new CommandException("", 69);
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -154,12 +161,13 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().Be(69);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().BeEmpty();
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Should().ContainAllInOrder(
             "CliFx.Exceptions.CommandException",
             "at", "CliFx."
@@ -167,19 +175,20 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Command_can_throw_a_special_exception_which_prints_help_text_before_exiting()
+    public async Task I_can_throw_an_exception_in_a_command_to_report_an_error_and_print_the_help_text()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console) =>
-        throw new CommandException(""Something went wrong"", 69, true);
-}
-");
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new CommandException("Something went wrong", 69, true);
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -193,12 +202,13 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().Be(69);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().Contain("This will be in help text");
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Trim().Should().Be("Something went wrong");
     }
 }

CliFx.Tests/ParameterBindingSpecs.cs

@@ -16,29 +16,31 @@ public class ParameterBindingSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Parameter_is_bound_from_an_argument_matching_its_order()
+    public async Task I_can_bind_a_parameter_to_a_property_and_get_the_value_from_the_corresponding_argument()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""Foo = "" + Foo);
-        console.Output.WriteLine(""Bar = "" + Bar);
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("Foo = " + Foo);
+                    console.Output.WriteLine("Bar = " + Bar);
 
-        return default;
-    }
-}");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -51,10 +53,10 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().ConsistOfLines(
             "Foo = one",
             "Bar = two"
@@ -62,38 +64,40 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Parameter_of_non_scalar_type_is_bound_from_remaining_non_option_arguments()
+    public async Task I_can_bind_a_parameter_to_a_non_scalar_property_and_get_values_from_the_remaining_non_option_arguments()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    [CommandParameter(2)]
-    public IReadOnlyList<string> Baz { get; set; }
+                [CommandParameter(2)]
+                public required IReadOnlyList<string> Baz { get; init; }
 
-    [CommandOption(""boo"")]
-    public string Boo { get; set; }
+                [CommandOption("boo")]
+                public string? Boo { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""Foo = "" + Foo);
-        console.Output.WriteLine(""Bar = "" + Bar);
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("Foo = " + Foo);
+                    console.Output.WriteLine("Bar = " + Bar);
 
-        foreach (var i in Baz)
-            console.Output.WriteLine(""Baz = "" + i);
+                    foreach (var i in Baz)
+                        console.Output.WriteLine("Baz = " + i);
 
-        return default;
-    }
-}");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -106,10 +110,10 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().ConsistOfLines(
             "Foo = one",
             "Bar = two",
@@ -120,29 +124,109 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Parameter_is_not_bound_if_there_are_no_arguments_matching_its_order()
+    public async Task I_can_bind_a_parameter_to_a_property_and_get_an_error_if_the_user_does_not_provide_the_corresponding_argument()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1, IsRequired = false)]
-    public string Bar { get; set; } = ""xyz"";
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""Foo = "" + Foo);
-        console.Output.WriteLine(""Bar = "" + Bar);
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
 
-        return default;
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"one"},
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Missing required parameter(s)");
     }
-}");
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_to_a_non_scalar_property_and_get_an_error_if_the_user_does_not_provide_at_least_one_corresponding_argument()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                [CommandParameter(1)]
+                public required IReadOnlyList<string> Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            new[] {"one"},
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Missing required parameter(s)");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_non_required_parameter_to_a_property_and_get_no_value_if_the_user_does_not_provide_the_corresponding_argument()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                [CommandParameter(1, IsRequired = false)]
+                public string? Bar { get; init; } = "xyz";
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("Foo = " + Foo);
+                    console.Output.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -155,10 +239,10 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Should().ConsistOfLines(
             "Foo = abc",
             "Bar = xyz"
@@ -166,98 +250,26 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Parameter_binding_fails_if_a_required_parameter_has_not_been_provided()
+    public async Task I_can_bind_parameters_and_get_an_error_if_the_user_provides_too_many_arguments()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
 
-    [CommandParameter(1)]
-    public string Bar { get; set; }
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}");
-
-        var application = new CliApplicationBuilder()
-            .AddCommand(commandType)
-            .UseConsole(FakeConsole)
-            .Build();
-
-        // Act
-        var exitCode = await application.RunAsync(
-            new[] {"one"},
-            new Dictionary<string, string>()
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
         );
 
-        var stdErr = FakeConsole.ReadErrorString();
-
-        // Assert
-        exitCode.Should().NotBe(0);
-        stdErr.Should().Contain("Missing required parameter(s)");
-    }
-
-    [Fact]
-    public async Task Parameter_binding_fails_if_a_parameter_of_non_scalar_type_has_not_been_provided_with_at_least_one_value()
-    {
-        // Arrange
-        var commandType = DynamicCommandBuilder.Compile(
-            // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
-
-    [CommandParameter(1)]
-    public IReadOnlyList<string> Bar { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}");
-
-        var application = new CliApplicationBuilder()
-            .AddCommand(commandType)
-            .UseConsole(FakeConsole)
-            .Build();
-
-        // Act
-        var exitCode = await application.RunAsync(
-            new[] {"one"},
-            new Dictionary<string, string>()
-        );
-
-        var stdErr = FakeConsole.ReadErrorString();
-
-        // Assert
-        exitCode.Should().NotBe(0);
-        stdErr.Should().Contain("Missing required parameter(s)");
-    }
-
-    [Fact]
-    public async Task Parameter_binding_fails_if_one_of_the_provided_parameters_is_unexpected()
-    {
-        // Arrange
-        var commandType = DynamicCommandBuilder.Compile(
-            // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    [CommandParameter(0)]
-    public string Foo { get; set; }
-
-    [CommandParameter(1)]
-    public string Bar { get; set; }
-
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}");
-
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
             .UseConsole(FakeConsole)
@@ -269,10 +281,10 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Should().Contain("Unexpected parameter(s)");
     }
 }

CliFx.Tests/RoutingSpecs.cs

@@ -16,42 +16,43 @@ public class RoutingSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Default_command_is_executed_if_provided_arguments_do_not_match_any_named_command()
+    public async Task I_can_configure_a_command_to_be_executed_by_default_when_the_user_does_not_specify_a_command_name()
     {
         // Arrange
         var commandTypes = DynamicCommandBuilder.CompileMany(
             // language=cs
-            @"
-[Command]
-public class DefaultCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""default"");
-        return default;
-    }
-}
+            """
+            [Command]
+            public class DefaultCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("default");
+                    return default;
+                }
+            }
 
-[Command(""cmd"")]
-public class NamedCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""cmd"");
-        return default;
-    }
-}
+            [Command("cmd")]
+            public class NamedCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("cmd");
+                    return default;
+                }
+            }
 
-[Command(""cmd child"")]
-public class NamedChildCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""cmd child"");
-        return default;
-    }
-}
-");
+            [Command("cmd child")]
+            public class NamedChildCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("cmd child");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommands(commandTypes)
@@ -64,50 +65,51 @@ public class NamedChildCommand : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Trim().Should().Be("default");
     }
 
     [Fact]
-    public async Task Specific_named_command_is_executed_if_provided_arguments_match_its_name()
+    public async Task I_can_configure_a_command_to_be_executed_when_the_user_specifies_its_name()
     {
         // Arrange
         var commandTypes = DynamicCommandBuilder.CompileMany(
             // language=cs
-            @"
-[Command]
-public class DefaultCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""default"");
-        return default;
-    }
-}
+            """
+            [Command]
+            public class DefaultCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("default");
+                    return default;
+                }
+            }
 
-[Command(""cmd"")]
-public class NamedCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""cmd"");
-        return default;
-    }
-}
+            [Command("cmd")]
+            public class NamedCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("cmd");
+                    return default;
+                }
+            }
 
-[Command(""cmd child"")]
-public class NamedChildCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""cmd child"");
-        return default;
-    }
-}
-");
+            [Command("cmd child")]
+            public class NamedChildCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("cmd child");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommands(commandTypes)
@@ -120,50 +122,51 @@ public class NamedChildCommand : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Trim().Should().Be("cmd");
     }
 
     [Fact]
-    public async Task Specific_named_child_command_is_executed_if_provided_arguments_match_its_name()
+    public async Task I_can_configure_a_nested_command_to_be_executed_when_the_user_specifies_its_name()
     {
         // Arrange
         var commandTypes = DynamicCommandBuilder.CompileMany(
             // language=cs
-            @"
-[Command]
-public class DefaultCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""default"");
-        return default;
-    }
-}
+            """
+            [Command]
+            public class DefaultCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("default");
+                    return default;
+                }
+            }
 
-[Command(""cmd"")]
-public class NamedCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""cmd"");
-        return default;
-    }
-}
+            [Command("cmd")]
+            public class NamedCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("cmd");
+                    return default;
+                }
+            }
 
-[Command(""cmd child"")]
-public class NamedChildCommand : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""cmd child"");
-        return default;
-    }
-}
-");
+            [Command("cmd child")]
+            public class NamedChildCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("cmd child");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommands(commandTypes)
@@ -176,10 +179,10 @@ public class NamedChildCommand : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Trim().Should().Be("cmd child");
     }
 }

CliFx.Tests/TypeActivationSpecs.cs

@@ -4,6 +4,7 @@ using System.Threading.Tasks;
 using CliFx.Infrastructure;
 using CliFx.Tests.Utils;
 using FluentAssertions;
+using Microsoft.Extensions.DependencyInjection;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -17,21 +18,23 @@ public class TypeActivationSpecs : SpecsBase
     }
 
     [Fact]
-    public async Task Default_type_activator_can_initialize_a_type_if_it_has_a_parameterless_constructor()
+    public async Task I_can_configure_the_application_to_use_the_default_type_activator_to_initialize_types_through_parameterless_constructors()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""foo"");
-        return default;
-    }
-}");
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("foo");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -45,27 +48,29 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
         stdOut.Trim().Should().Be("foo");
     }
 
     [Fact]
-    public async Task Default_type_activator_fails_if_the_type_does_not_have_a_parameterless_constructor()
+    public async Task I_can_configure_the_application_to_use_the_default_type_activator_and_get_an_error_if_the_requested_type_does_not_have_a_parameterless_constructor()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public Command(string foo) {}
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public Command(string foo) {}
 
-    public ValueTask ExecuteAsync(IConsole console) => default;
-}");
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
@@ -79,38 +84,40 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdErr = FakeConsole.ReadErrorString();
-
         // Assert
         exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Should().Contain("Failed to create an instance of type");
     }
 
     [Fact]
-    public async Task Delegate_type_activator_can_initialize_a_type_using_a_custom_function()
+    public async Task I_can_configure_the_application_to_use_a_custom_type_activator_to_initialize_types_using_a_delegate()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    private readonly string _foo;
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                private readonly string _foo;
 
-    public Command(string foo) => _foo = foo;
+                public Command(string foo) => _foo = foo;
 
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(_foo);
-        return default;
-    }
-}");
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine(_foo);
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
             .UseConsole(FakeConsole)
-            .UseTypeActivator(type => Activator.CreateInstance(type, "hello world")!)
+            .UseTypeActivator(type => Activator.CreateInstance(type, "Hello world")!)
             .Build();
 
         // Act
@@ -119,34 +126,53 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdOut = FakeConsole.ReadOutputString();
-
         // Assert
         exitCode.Should().Be(0);
-        stdOut.Trim().Should().Be("hello world");
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("Hello world");
     }
 
     [Fact]
-    public async Task Delegate_type_activator_fails_if_the_underlying_function_returns_null()
+    public async Task I_can_configure_the_application_to_use_a_custom_type_activator_to_initialize_types_using_a_service_provider()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
             // language=cs
-            @"
-[Command]
-public class Command : ICommand
-{
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        console.Output.WriteLine(""foo"");
-        return default;
-    }
-}");
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                private readonly string _foo;
+
+                public Command(string foo) => _foo = foo;
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine(_foo);
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
             .UseConsole(FakeConsole)
-            .UseTypeActivator(_ => null!)
+            .UseTypeActivator(commandTypes =>
+            {
+                var services = new ServiceCollection();
+
+                foreach (var serviceType in commandTypes)
+                {
+                    services.AddSingleton(
+                        serviceType,
+                        Activator.CreateInstance(serviceType, "Hello world")!
+                    );
+                }
+
+                return services.BuildServiceProvider();
+            })
             .Build();
 
         // Act
@@ -155,10 +181,48 @@ public class Command : ICommand
             new Dictionary<string, string>()
         );
 
-        var stdErr = FakeConsole.ReadErrorString();
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("Hello world");
+    }
+
+    [Fact]
+    public async Task I_can_configure_the_application_to_use_a_custom_type_activator_and_get_an_error_if_the_requested_type_cannot_be_initialized()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.Output.WriteLine("foo");
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator((Type _) => null!)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
 
         // Assert
         exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
         stdErr.Should().Contain("Failed to create an instance of type");
     }
 }

CliFx.Tests/Utils/DynamicCommandBuilder.cs

@@ -11,14 +11,9 @@ using Microsoft.CodeAnalysis.Text;
 namespace CliFx.Tests.Utils;
 
 // This class uses Roslyn to compile commands dynamically.
-//
-// It allows us to collocate commands with tests more
-// easily, which helps a lot when reasoning about them.
-// Unfortunately, this comes at a cost of static typing,
-// but this is still a worthwhile trade off.
-//
-// Maybe one day C# will allow declaring classes inside
-// methods and doing this will no longer be necessary.
+// It allows us to collocate commands with tests more easily, which helps a lot when reasoning about them.
+// Unfortunately, this comes at a cost of static typing, but this is still a worthwhile trade off.
+// Maybe one day C# will allow declaring classes inside methods and doing this will no longer be necessary.
 // Language proposal: https://github.com/dotnet/csharplang/discussions/130
 internal static class DynamicCommandBuilder
 {
@@ -61,7 +56,7 @@ internal static class DynamicCommandBuilder
         var compilation = CSharpCompilation.Create(
             "CliFxTests_DynamicAssembly_" + Guid.NewGuid(),
             new[] {ast},
-            ReferenceAssemblies.Net50
+            Net70.References.All
                 .Append(MetadataReference.CreateFromFile(typeof(ICommand).Assembly.Location))
                 .Append(MetadataReference.CreateFromFile(typeof(DynamicCommandBuilder).Assembly.Location)),
             // DLL to avoid having to define the Main() method
@@ -76,9 +71,10 @@ internal static class DynamicCommandBuilder
         if (compilationErrors.Any())
         {
             throw new InvalidOperationException(
-                "Failed to compile code." +
-                Environment.NewLine +
-                string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))
+                $"""
+                Failed to compile code.
+                {string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))}
+                """
             );
         }
 
@@ -94,9 +90,10 @@ internal static class DynamicCommandBuilder
         if (emitErrors.Any())
         {
             throw new InvalidOperationException(
-                "Failed to emit code." +
-                Environment.NewLine +
-                string.Join(Environment.NewLine, emitErrors.Select(e => e.ToString()))
+                $"""
+                Failed to emit code.
+                {string.Join(Environment.NewLine, emitErrors.Select(e => e.ToString()))}
+                """
             );
         }
 
@@ -122,7 +119,6 @@ internal static class DynamicCommandBuilder
     public static Type Compile(string sourceCode)
     {
         var commandTypes = CompileMany(sourceCode);
-
         if (commandTypes.Count > 1)
         {
             throw new InvalidOperationException(

CliFx.Tests/Utils/Extensions/AssertionExtensions.cs

@@ -41,7 +41,7 @@ internal static class AssertionExtensions
             lastIndex = index;
         }
 
-        return new(assertions);
+        return new AndConstraint<StringAssertions>(assertions);
     }
 
     public static AndConstraint<StringAssertions> ContainAllInOrder(

CliFx.Tests/Utils/NoOpCommand.cs

@@ -5,7 +5,7 @@ using CliFx.Infrastructure;
 namespace CliFx.Tests.Utils;
 
 [Command]
-public class NoOpCommand : ICommand
+internal class NoOpCommand : ICommand
 {
     public ValueTask ExecuteAsync(IConsole console) => default;
 }

CliFx/ApplicationConfiguration.cs

@@ -9,22 +9,22 @@ namespace CliFx;
 public class ApplicationConfiguration
 {
     /// <summary>
-    /// Command types defined in this application.
+    /// Command types defined in the application.
     /// </summary>
     public IReadOnlyList<Type> CommandTypes { get; }
 
     /// <summary>
-    /// Whether debug mode is allowed in this application.
+    /// Whether debug mode is allowed in the application.
     /// </summary>
     public bool IsDebugModeAllowed { get; }
 
     /// <summary>
-    /// Whether preview mode is allowed in this application.
+    /// Whether preview mode is allowed in the application.
     /// </summary>
     public bool IsPreviewModeAllowed { get; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="ApplicationConfiguration"/>.
+    /// Initializes an instance of <see cref="ApplicationConfiguration" />.
     /// </summary>
     public ApplicationConfiguration(
         IReadOnlyList<Type> commandTypes,

CliFx/ApplicationMetadata.cs

@@ -26,7 +26,7 @@ public class ApplicationMetadata
     public string? Description { get; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="ApplicationMetadata"/>.
+    /// Initializes an instance of <see cref="ApplicationMetadata" />.
     /// </summary>
     public ApplicationMetadata(
         string title,

CliFx/Attributes/CommandAttribute.cs

@@ -9,13 +9,12 @@ namespace CliFx.Attributes;
 public sealed class CommandAttribute : Attribute
 {
     /// <summary>
-    /// Command's name.
+    /// Command name.
     /// </summary>
     /// <remarks>
-    /// Command can have no name, in which case it's treated as the default command.
-    ///
+    /// Command can have no name, in which case it's treated as the application's default command.
+    /// Only one default command is allowed in an application.
     /// All commands registered in an application must have unique names (comparison IS NOT case-sensitive).
-    /// Only one command without a name is allowed in an application.
     /// </remarks>
     public string? Name { get; }
 
@@ -26,7 +25,7 @@ public sealed class CommandAttribute : Attribute
     public string? Description { get; set; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="CommandAttribute"/>.
+    /// Initializes an instance of <see cref="CommandAttribute" />.
     /// </summary>
     public CommandAttribute(string name)
     {
@@ -34,7 +33,7 @@ public sealed class CommandAttribute : Attribute
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="CommandAttribute"/>.
+    /// Initializes an instance of <see cref="CommandAttribute" />.
     /// </summary>
     public CommandAttribute()
     {

CliFx/Attributes/CommandOptionAttribute.cs

@@ -14,7 +14,7 @@ public sealed class CommandOptionAttribute : Attribute
     /// </summary>
     /// <remarks>
     /// Must contain at least two characters and start with a letter.
-    /// Either <see cref="Name"/> or <see cref="ShortName"/> must be set.
+    /// Either <see cref="Name" /> or <see cref="ShortName" /> must be set.
     /// All options in a command must have unique names (comparison IS NOT case-sensitive).
     /// </remarks>
     public string? Name { get; }
@@ -23,7 +23,7 @@ public sealed class CommandOptionAttribute : Attribute
     /// Option short name.
     /// </summary>
     /// <remarks>
-    /// Either <see cref="Name"/> or <see cref="ShortName"/> must be set.
+    /// Either <see cref="Name" /> or <see cref="ShortName" /> must be set.
     /// All options in a command must have unique short names (comparison IS case-sensitive).
     /// </remarks>
     public char? ShortName { get; }
@@ -32,11 +32,15 @@ public sealed class CommandOptionAttribute : Attribute
     /// Whether this option is required (default: <c>false</c>).
     /// If an option is required, the user will get an error if they don't set it.
     /// </summary>
+    /// <remarks>
+    /// You can use the <c>required</c> keyword on the property (introduced in C# 11) to implicitly
+    /// set <see cref="IsRequired" /> to <c>true</c>.
+    /// </remarks>
     public bool IsRequired { get; set; }
 
     /// <summary>
     /// Environment variable whose value will be used as a fallback if the option
-    /// has not been explicitly set through command line arguments.
+    /// has not been explicitly set through command-line arguments.
     /// </summary>
     public string? EnvironmentVariable { get; set; }
 
@@ -47,11 +51,11 @@ public sealed class CommandOptionAttribute : Attribute
     public string? Description { get; set; }
 
     /// <summary>
-    /// Custom converter used for mapping the raw command line argument into
+    /// Custom converter used for mapping the raw command-line argument into
     /// a value expected by the underlying property.
     /// </summary>
     /// <remarks>
-    /// Converter must derive from <see cref="BindingConverter{T}"/>.
+    /// Converter must derive from <see cref="BindingConverter{T}" />.
     /// </remarks>
     public Type? Converter { get; set; }
 
@@ -60,12 +64,12 @@ public sealed class CommandOptionAttribute : Attribute
     /// property, after it has been bound.
     /// </summary>
     /// <remarks>
-    /// Validators must derive from <see cref="BindingValidator{T}"/>.
+    /// Validators must derive from <see cref="BindingValidator{T}" />.
     /// </remarks>
     public Type[] Validators { get; set; } = Array.Empty<Type>();
 
     /// <summary>
-    /// Initializes an instance of <see cref="CommandOptionAttribute"/>.
+    /// Initializes an instance of <see cref="CommandOptionAttribute" />.
     /// </summary>
     private CommandOptionAttribute(string? name, char? shortName)
     {
@@ -74,15 +78,15 @@ public sealed class CommandOptionAttribute : Attribute
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="CommandOptionAttribute"/>.
+    /// Initializes an instance of <see cref="CommandOptionAttribute" />.
     /// </summary>
     public CommandOptionAttribute(string name, char shortName)
-        : this(name, (char?) shortName)
+        : this(name, (char?)shortName)
     {
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="CommandOptionAttribute"/>.
+    /// Initializes an instance of <see cref="CommandOptionAttribute" />.
     /// </summary>
     public CommandOptionAttribute(string name)
         : this(name, null)
@@ -90,10 +94,10 @@ public sealed class CommandOptionAttribute : Attribute
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="CommandOptionAttribute"/>.
+    /// Initializes an instance of <see cref="CommandOptionAttribute" />.
     /// </summary>
     public CommandOptionAttribute(char shortName)
-        : this(null, (char?) shortName)
+        : this(null, (char?)shortName)
     {
     }
 }

CliFx/Attributes/CommandParameterAttribute.cs

@@ -11,8 +11,7 @@ public sealed class CommandParameterAttribute : Attribute
 {
     /// <summary>
     /// Parameter order.
-    /// Higher order means the parameter appears later, lower order means
-    /// it appears earlier.
+    /// Higher order means the parameter appears later, lower order means it appears earlier.
     /// </summary>
     /// <remarks>
     /// All parameters in a command must have unique order.
@@ -47,11 +46,11 @@ public sealed class CommandParameterAttribute : Attribute
     public string? Description { get; set; }
 
     /// <summary>
-    /// Custom converter used for mapping the raw command line argument into
+    /// Custom converter used for mapping the raw command-line argument into
     /// a value expected by the underlying property.
     /// </summary>
     /// <remarks>
-    /// Converter must derive from <see cref="BindingConverter{T}"/>.
+    /// Converter must derive from <see cref="BindingConverter{T}" />.
     /// </remarks>
     public Type? Converter { get; set; }
 
@@ -60,12 +59,12 @@ public sealed class CommandParameterAttribute : Attribute
     /// property, after it has been bound.
     /// </summary>
     /// <remarks>
-    /// Validators must derive from <see cref="BindingValidator{T}"/>.
+    /// Validators must derive from <see cref="BindingValidator{T}" />.
     /// </remarks>
     public Type[] Validators { get; set; } = Array.Empty<Type>();
 
     /// <summary>
-    /// Initializes an instance of <see cref="CommandParameterAttribute"/>.
+    /// Initializes an instance of <see cref="CommandParameterAttribute" />.
     /// </summary>
     public CommandParameterAttribute(int order)
     {

CliFx/CliApplication.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using CliFx.Exceptions;
 using CliFx.Formatting;
@@ -14,7 +15,7 @@ using CliFx.Utils.Extensions;
 namespace CliFx;
 
 /// <summary>
-/// Command line application facade.
+/// Command-line application facade.
 /// </summary>
 public class CliApplication
 {
@@ -34,7 +35,7 @@ public class CliApplication
     private readonly CommandBinder _commandBinder;
 
     /// <summary>
-    /// Initializes an instance of <see cref="CliApplication"/>.
+    /// Initializes an instance of <see cref="CliApplication" />.
     /// </summary>
     public CliApplication(
         ApplicationMetadata metadata,
@@ -58,12 +59,8 @@ public class CliApplication
 
     private bool ShouldShowHelpText(CommandSchema commandSchema, CommandInput commandInput) =>
         commandSchema.IsHelpOptionAvailable && commandInput.IsHelpOptionSpecified ||
-        // Show help text also in case the fallback default command is
-        // executed without any arguments.
-        commandSchema == FallbackDefaultCommand.Schema &&
-        string.IsNullOrWhiteSpace(commandInput.CommandName) &&
-        !commandInput.Parameters.Any() &&
-        !commandInput.Options.Any();
+        // Show help text also if the fallback default command is executed without any arguments
+        commandSchema == FallbackDefaultCommand.Schema && !commandInput.HasArguments;
 
     private bool ShouldShowVersionText(CommandSchema commandSchema, CommandInput commandInput) =>
         commandSchema.IsVersionOptionAvailable && commandInput.IsVersionOptionSpecified;
@@ -75,28 +72,30 @@ public class CliApplication
             var processId = ProcessEx.GetCurrentProcessId();
 
             _console.Output.WriteLine(
-                $"Attach debugger to PID {processId} to continue."
+                $"Attach the debugger to process with ID {processId} to continue."
             );
         }
 
-        // Try to also launch debugger ourselves (only works if VS is installed)
+        // Try to also launch the debugger ourselves (only works with Visual Studio)
         Debugger.Launch();
 
         while (!Debugger.IsAttached)
-        {
             await Task.Delay(100);
-        }
     }
 
     private async ValueTask<int> RunAsync(ApplicationSchema applicationSchema, CommandInput commandInput)
     {
-        // Handle debug directive
+        // Console colors may have already been overridden by the parent process,
+        // so we need to reset it to make sure that everything we write looks properly.
+        _console.ResetColor();
+
+        // Handle the debug directive
         if (IsDebugModeEnabled(commandInput))
         {
             await PromptDebuggerAsync();
         }
 
-        // Handle preview directive
+        // Handle the preview directive
         if (IsPreviewModeEnabled(commandInput))
         {
             _console.Output.WriteCommandInput(commandInput);
@@ -105,16 +104,23 @@ public class CliApplication
 
         // Try to get the command schema that matches the input
         var commandSchema =
-            applicationSchema.TryFindCommand(commandInput.CommandName) ??
-            applicationSchema.TryFindDefaultCommand() ??
+            (!string.IsNullOrWhiteSpace(commandInput.CommandName)
+                // If the command name is specified, try to find the command by name.
+                // This should always succeed, because the input parsing relies on
+                // the list of available command names.
+                ? applicationSchema.TryFindCommand(commandInput.CommandName)
+                // Otherwise, try to find the default command
+                : applicationSchema.TryFindDefaultCommand()) ??
+            // If a valid command was not found, use the fallback default command.
+            // This is only used as a stub to show the help text.
             FallbackDefaultCommand.Schema;
 
-        // Activate command instance
+        // Initialize an instance of the command type
         var commandInstance = commandSchema == FallbackDefaultCommand.Schema
-            ? new FallbackDefaultCommand() // bypass activator
-            : (ICommand)_typeActivator.CreateInstance(commandSchema.Type);
+            ? new FallbackDefaultCommand() // bypass the activator
+            : _typeActivator.CreateInstance<ICommand>(commandSchema.Type);
 
-        // Assemble help context
+        // Assemble the help context
         var helpContext = new HelpContext(
             Metadata,
             applicationSchema,
@@ -122,14 +128,14 @@ public class CliApplication
             commandSchema.GetValues(commandInstance)
         );
 
-        // Handle help option
+        // Handle the help option
         if (ShouldShowHelpText(commandSchema, commandInput))
         {
             _console.Output.WriteHelpText(helpContext);
             return 0;
         }
 
-        // Handle version option
+        // Handle the version option
         if (ShouldShowVersionText(commandSchema, commandInput))
         {
             _console.Output.WriteLine(Metadata.Version);
@@ -137,12 +143,12 @@ public class CliApplication
         }
 
         // Starting from this point, we may produce exceptions that are meant for the
-        // end user of the application (i.e. invalid input, command exception, etc).
+        // end-user of the application (i.e. invalid input, command exception, etc).
         // Catch these exceptions here, print them to the console, and don't let them
         // propagate further.
         try
         {
-            // Bind and execute command
+            // Bind and execute the command
             _commandBinder.Bind(commandInput, commandSchema, commandInstance);
             await commandInstance.ExecuteAsync(_console);
 
@@ -163,12 +169,12 @@ public class CliApplication
     }
 
     /// <summary>
-    /// Runs the application with the specified command line arguments and environment variables.
-    /// Returns an exit code which indicates whether the application completed successfully.
+    /// Runs the application with the specified command-line arguments and environment variables.
+    /// Returns the exit code which indicates whether the application completed successfully.
     /// </summary>
     /// <remarks>
-    /// When running WITHOUT debugger (i.e. in production), this method swallows all exceptions and
-    /// reports them to the console.
+    /// When running WITHOUT the debugger attached (i.e. in production), this method swallows
+    /// all exceptions and reports them to the console.
     /// </remarks>
     public async ValueTask<int> RunAsync(
         IReadOnlyList<string> commandLineArguments,
@@ -176,10 +182,6 @@ public class CliApplication
     {
         try
         {
-            // Console colors may have already been overridden by the parent process,
-            // so we need to reset it to make sure that everything we write looks properly.
-            _console.ResetColor();
-
             var applicationSchema = ApplicationSchema.Resolve(Configuration.CommandTypes);
 
             var commandInput = CommandInput.Parse(
@@ -192,10 +194,8 @@ public class CliApplication
         }
         // To prevent the app from showing the annoying troubleshooting dialog on Windows,
         // we handle all exceptions ourselves and print them to the console.
-        //
         // We only want to do that if the app is running in production, which we infer
-        // based on whether a debugger is attached to the process.
-        //
+        // based on whether the debugger is attached to the process.
         // When not running in production, we want the IDE to show exceptions to the
         // developer, so we don't swallow them in that case.
         catch (Exception ex) when (!Debugger.IsAttached)
@@ -206,31 +206,32 @@ public class CliApplication
     }
 
     /// <summary>
-    /// Runs the application with the specified command line arguments.
-    /// Environment variables are resolved automatically.
-    /// Returns an exit code which indicates whether the application completed successfully.
+    /// Runs the application with the specified command-line arguments.
+    /// Returns the exit code which indicates whether the application completed successfully.
     /// </summary>
     /// <remarks>
-    /// When running WITHOUT debugger (i.e. in production), this method swallows all exceptions and
-    /// reports them to the console.
+    /// When running WITHOUT the debugger attached (i.e. in production), this method swallows
+    /// all exceptions and reports them to the console.
     /// </remarks>
     public async ValueTask<int> RunAsync(IReadOnlyList<string> commandLineArguments) => await RunAsync(
         commandLineArguments,
-        // Use case-sensitive comparison because environment variables are
-        // case-sensitive on Linux and macOS (but not on Windows).
         Environment
             .GetEnvironmentVariables()
-            .ToDictionary<string, string>(StringComparer.Ordinal)
+            .ToDictionary<string, string>(
+                RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+                    ? StringComparer.OrdinalIgnoreCase
+                    : StringComparer.Ordinal
+            )
     );
 
     /// <summary>
     /// Runs the application.
-    /// Command line arguments and environment variables are resolved automatically.
-    /// Returns an exit code which indicates whether the application completed successfully.
+    /// Command-line arguments and environment variables are resolved automatically.
+    /// Returns the exit code which indicates whether the application completed successfully.
     /// </summary>
     /// <remarks>
-    /// When running WITHOUT debugger (i.e. in production), this method swallows all exceptions and
-    /// reports them to the console.
+    /// When running WITHOUT the debugger attached (i.e. in production), this method swallows
+    /// all exceptions and reports them to the console.
     /// </remarks>
     public async ValueTask<int> RunAsync() => await RunAsync(
         Environment.GetCommandLineArgs()

CliFx/CliApplicationBuilder.cs

@@ -12,7 +12,7 @@ using CliFx.Utils.Extensions;
 namespace CliFx;
 
 /// <summary>
-/// Builder for <see cref="CliApplication"/>.
+/// Builder for <see cref="CliApplication" />.
 /// </summary>
 public partial class CliApplicationBuilder
 {
@@ -33,7 +33,6 @@ public partial class CliApplicationBuilder
     public CliApplicationBuilder AddCommand(Type commandType)
     {
         _commandTypes.Add(commandType);
-
         return this;
     }
 
@@ -58,8 +57,8 @@ public partial class CliApplicationBuilder
     /// Adds commands from the specified assembly to the application.
     /// </summary>
     /// <remarks>
-    /// This method looks for public non-abstract classes that implement <see cref="ICommand"/>
-    /// and are annotated by <see cref="CommandAttribute"/>.
+    /// This method looks for public non-abstract classes that implement <see cref="ICommand" />
+    /// and are annotated by <see cref="CommandAttribute" />.
     /// </remarks>
     public CliApplicationBuilder AddCommandsFrom(Assembly commandAssembly)
     {
@@ -73,8 +72,8 @@ public partial class CliApplicationBuilder
     /// Adds commands from the specified assemblies to the application.
     /// </summary>
     /// <remarks>
-    /// This method looks for public non-abstract classes that implement <see cref="ICommand"/>
-    /// and are annotated by <see cref="CommandAttribute"/>.
+    /// This method looks for public non-abstract classes that implement <see cref="ICommand" />
+    /// and are annotated by <see cref="CommandAttribute" />.
     /// </remarks>
     public CliApplicationBuilder AddCommandsFrom(IEnumerable<Assembly> commandAssemblies)
     {
@@ -88,8 +87,8 @@ public partial class CliApplicationBuilder
     /// Adds commands from the calling assembly to the application.
     /// </summary>
     /// <remarks>
-    /// This method looks for public non-abstract classes that implement <see cref="ICommand"/>
-    /// and are annotated by <see cref="CommandAttribute"/>.
+    /// This method looks for public non-abstract classes that implement <see cref="ICommand" />
+    /// and are annotated by <see cref="CommandAttribute" />.
     /// </remarks>
     public CliApplicationBuilder AddCommandsFromThisAssembly() => AddCommandsFrom(Assembly.GetCallingAssembly());
 
@@ -112,7 +111,7 @@ public partial class CliApplicationBuilder
     }
 
     /// <summary>
-    /// Sets application title, which is shown in the help text.
+    /// Sets the application title, which is shown in the help text.
     /// </summary>
     /// <remarks>
     /// By default, application title is inferred from the assembly name.
@@ -124,11 +123,10 @@ public partial class CliApplicationBuilder
     }
 
     /// <summary>
-    /// Sets application executable name, which is shown in the help text.
+    /// Sets the application executable name, which is shown in the help text.
     /// </summary>
     /// <remarks>
     /// By default, application executable name is inferred from the assembly file name.
-    /// The file name is also prefixed with `dotnet` if it's a DLL file.
     /// </remarks>
     public CliApplicationBuilder SetExecutableName(string executableName)
     {
@@ -137,8 +135,7 @@ public partial class CliApplicationBuilder
     }
 
     /// <summary>
-    /// Sets application version, which is shown in the help text or
-    /// when the user specifies the version option.
+    /// Sets the application version, which is shown in the help text or when the user specifies the version option.
     /// </summary>
     /// <remarks>
     /// By default, application version is inferred from the assembly version.
@@ -150,7 +147,7 @@ public partial class CliApplicationBuilder
     }
 
     /// <summary>
-    /// Sets application description, which is shown in the help text.
+    /// Sets the application description, which is shown in the help text.
     /// </summary>
     public CliApplicationBuilder SetDescription(string? description)
     {
@@ -159,7 +156,7 @@ public partial class CliApplicationBuilder
     }
 
     /// <summary>
-    /// Configures the application to use the specified implementation of <see cref="IConsole"/>.
+    /// Configures the application to use the specified implementation of <see cref="IConsole" />.
     /// </summary>
     public CliApplicationBuilder UseConsole(IConsole console)
     {
@@ -168,7 +165,7 @@ public partial class CliApplicationBuilder
     }
 
     /// <summary>
-    /// Configures the application to use the specified implementation of <see cref="ITypeActivator"/>.
+    /// Configures the application to use the specified implementation of <see cref="ITypeActivator" />.
     /// </summary>
     public CliApplicationBuilder UseTypeActivator(ITypeActivator typeActivator)
     {
@@ -177,13 +174,27 @@ public partial class CliApplicationBuilder
     }
 
     /// <summary>
-    /// Configures the application to use the specified function for activating types.
+    /// Configures the application to use the specified delegate for activating types.
     /// </summary>
-    public CliApplicationBuilder UseTypeActivator(Func<Type, object> typeActivator) =>
-        UseTypeActivator(new DelegateTypeActivator(typeActivator));
+    public CliApplicationBuilder UseTypeActivator(Func<Type, object> createInstance) =>
+        UseTypeActivator(new DelegateTypeActivator(createInstance));
 
     /// <summary>
-    /// Creates a configured instance of <see cref="CliApplication"/>.
+    /// Configures the application to use the specified service provider for activating types.
+    /// </summary>
+    public CliApplicationBuilder UseTypeActivator(IServiceProvider serviceProvider) =>
+        UseTypeActivator(serviceProvider.GetService);
+
+    /// <summary>
+    /// Configures the application to use the specified service provider for activating types.
+    /// This method takes a delegate that receives the list of all added command types, so that you can
+    /// easily register them with the service provider.
+    /// </summary>
+    public CliApplicationBuilder UseTypeActivator(Func<IReadOnlyList<Type>, IServiceProvider> getServiceProvider) =>
+        UseTypeActivator(getServiceProvider(_commandTypes.ToArray()));
+
+    /// <summary>
+    /// Creates a configured instance of <see cref="CliApplication" />.
     /// </summary>
     public CliApplication Build()
     {
@@ -215,45 +226,58 @@ public partial class CliApplicationBuilder
     {
         var entryAssemblyName = EnvironmentEx.EntryAssembly?.GetName().Name;
         if (string.IsNullOrWhiteSpace(entryAssemblyName))
-            return "App";
+        {
+            throw new InvalidOperationException(
+                "Failed to infer the default application title. " +
+                $"Please specify it explicitly using {nameof(SetTitle)}()."
+            );
+        }
 
         return entryAssemblyName;
     }
 
     private static string GetDefaultExecutableName()
     {
-        var entryAssemblyLocation = EnvironmentEx.EntryAssembly?.Location;
-        if (string.IsNullOrWhiteSpace(entryAssemblyLocation))
-            return "app";
+        var entryAssemblyFilePath = EnvironmentEx.EntryAssembly?.Location;
+        var processFilePath = EnvironmentEx.ProcessPath;
 
-        // If the application was launched via matching EXE apphost, use that as the executable name
-        var isLaunchedViaAppHost = string.Equals(
-            EnvironmentEx.ProcessPath,
-            Path.ChangeExtension(entryAssemblyLocation, ".exe"),
-            StringComparison.OrdinalIgnoreCase
-        );
+        if (string.IsNullOrWhiteSpace(entryAssemblyFilePath) || string.IsNullOrWhiteSpace(processFilePath))
+        {
+            throw new InvalidOperationException(
+                "Failed to infer the default application executable name. " +
+                $"Please specify it explicitly using {nameof(SetExecutableName)}()."
+            );
+        }
 
-        if (isLaunchedViaAppHost)
-            return Path.GetFileNameWithoutExtension(entryAssemblyLocation);
+        // If the process path matches the entry assembly path, it's a legacy .NET Framework app
+        // or a self-contained .NET Core app.
+        if (PathEx.AreEqual(entryAssemblyFilePath, processFilePath))
+        {
+            return Path.GetFileNameWithoutExtension(entryAssemblyFilePath);
+        }
 
-        // Otherwise, use the entry assembly as the executable name.
-        // Prefix it with `dotnet` if it's a DLL file.
-        var isDll = string.Equals(
-            Path.GetExtension(entryAssemblyLocation),
-            ".dll",
-            StringComparison.OrdinalIgnoreCase
-        );
+        // If the process path has the same name and parent directory as the entry assembly path,
+        // but different extension, it's a framework-dependent .NET Core app launched through the apphost.
+        if (PathEx.AreEqual(Path.ChangeExtension(entryAssemblyFilePath, "exe"), processFilePath) ||
+            PathEx.AreEqual(Path.GetFileNameWithoutExtension(entryAssemblyFilePath), processFilePath))
+        {
+            return Path.GetFileNameWithoutExtension(entryAssemblyFilePath);
+        }
 
-        return isDll
-            ? "dotnet " + Path.GetFileName(entryAssemblyLocation)
-            : Path.GetFileNameWithoutExtension(entryAssemblyLocation);
+        // Otherwise, it's a framework-dependent .NET Core app launched through the .NET CLI
+        return "dotnet " + Path.GetFileName(entryAssemblyFilePath);
     }
 
     private static string GetDefaultVersionText()
     {
         var entryAssemblyVersion = EnvironmentEx.EntryAssembly?.GetName().Version;
         if (entryAssemblyVersion is null)
-            return "v1.0";
+        {
+            throw new InvalidOperationException(
+                "Failed to infer the default application version. " +
+                $"Please specify it explicitly using {nameof(SetVersion)}()."
+            );
+        }
 
         return "v" + entryAssemblyVersion.ToSemanticString();
     }

CliFx/CliFx.csproj

@@ -1,14 +1,16 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.1;netstandard2.0</TargetFrameworks>
-    <Authors>$(Company)</Authors>
-    <Description>Declarative framework for building command line applications</Description>
+    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
     <IsPackable>true</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <Authors>$(Company)</Authors>
+    <Description>Class-first framework for building command-line interfaces</Description>
     <PackageTags>command line executable interface framework parser arguments cli app application net core</PackageTags>
     <PackageProjectUrl>https://github.com/Tyrrrz/CliFx</PackageProjectUrl>
     <PackageReleaseNotes>https://github.com/Tyrrrz/CliFx/blob/master/Changelog.md</PackageReleaseNotes>
-    <PackageReadmeFile>Readme.md</PackageReadmeFile>
     <PackageIcon>favicon.png</PackageIcon>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
@@ -18,22 +20,19 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <None Include="../Readme.md" Pack="true" PackagePath="" Visible="false" />
     <None Include="../favicon.png" Pack="true" PackagePath="" Visible="false" />
   </ItemGroup>
 
   <ItemGroup>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="all" />
-    <PackageReference Include="Nullable" Version="1.3.0" PrivateAssets="all" />
+    <PackageReference Include="PolyShim" Version="1.2.0" PrivateAssets="all" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
-    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
-  </ItemGroup>
-
-  <!-- Pack the analyzer assembly inside the package -->
+  <!-- Embed the analyzer inside the package -->
   <ItemGroup>
     <ProjectReference Include="../CliFx.Analyzers/CliFx.Analyzers.csproj" ReferenceOutputAssembly="false" OutputItemType="analyzer" />
+    <None Include="../CliFx.Analyzers/bin/$(Configuration)/netstandard2.0/CliFx.Analyzers.deps.json" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
     <None Include="../CliFx.Analyzers/bin/$(Configuration)/netstandard2.0/CliFx.Analyzers.dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
     <None Include="../CliFx.Analyzers/bin/$(Configuration)/netstandard2.0/System.Buffers.dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
     <None Include="../CliFx.Analyzers/bin/$(Configuration)/netstandard2.0/System.Collections.Immutable.dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />

CliFx/CommandBinder.cs

@@ -27,11 +27,11 @@ internal class CommandBinder
         // Custom converter
         if (memberSchema.ConverterType is not null)
         {
-            var converter = (IBindingConverter)_typeActivator.CreateInstance(memberSchema.ConverterType);
+            var converter = _typeActivator.CreateInstance<IBindingConverter>(memberSchema.ConverterType);
             return converter.Convert(rawValue);
         }
 
-        // Assignable from string (e.g. string itself, object, etc)
+        // Assignable from a string (e.g. string itself, object, etc)
         if (targetType.IsAssignableFrom(typeof(string)))
         {
             return rawValue;
@@ -77,7 +77,7 @@ internal class CommandBinder
                 : null;
         }
 
-        // String-constructible (FileInfo, etc)
+        // String-constructable (FileInfo, etc)
         var stringConstructor = targetType.GetConstructor(new[] { typeof(string) });
         if (stringConstructor is not null)
         {
@@ -99,11 +99,11 @@ internal class CommandBinder
         }
 
         throw CliFxException.InternalError(
-            $"{memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} has an unsupported underlying property type." +
-            Environment.NewLine +
-            $"There is no known way to convert a string value into an instance of type `{targetType.FullName}`." +
-            Environment.NewLine +
-            "To fix this, either change the property to use a supported type or configure a custom converter."
+            $"""
+            {memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} has an unsupported underlying property type.
+            There is no known way to convert a string value into an instance of type `{targetType.FullName}`.
+            To fix this, either change the property to use a supported type or configure a custom converter.
+            """
         );
     }
 
@@ -125,7 +125,7 @@ internal class CommandBinder
             return array;
         }
 
-        // Array-constructible (List<T>, HashSet<T>, etc)
+        // Array-constructable (List<T>, HashSet<T>, etc)
         var arrayConstructor = targetEnumerableType.GetConstructor(new[] { arrayType });
         if (arrayConstructor is not null)
         {
@@ -133,56 +133,64 @@ internal class CommandBinder
         }
 
         throw CliFxException.InternalError(
-            $"{memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} has an unsupported underlying property type." +
-            Environment.NewLine +
-            $"There is no known way to convert an array of `{targetElementType.FullName}` into an instance of type `{targetEnumerableType.FullName}`." +
-            Environment.NewLine +
-            "To fix this, change the property to use a type which can be assigned from an array or a type that has a constructor which accepts an array."
+            $"""
+            {memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} has an unsupported underlying property type.
+            There is no known way to convert an array of `{targetElementType.FullName}` into an instance of type `{targetEnumerableType.FullName}`.
+            To fix this, change the property to use a type which can be assigned from an array or a type which has a constructor that accepts an array.
+            """
         );
     }
 
     private object? ConvertMember(IMemberSchema memberSchema, IReadOnlyList<string> rawValues)
     {
-        var targetType = memberSchema.Property.Type;
-
         try
         {
             // Non-scalar
-            var enumerableUnderlyingType = targetType.TryGetEnumerableUnderlyingType();
-            if (targetType != typeof(string) && enumerableUnderlyingType is not null)
+            var enumerableUnderlyingType = memberSchema.Property.Type.TryGetEnumerableUnderlyingType();
+            if (enumerableUnderlyingType is not null && memberSchema.Property.Type != typeof(string))
             {
-                return ConvertMultiple(memberSchema, rawValues, targetType, enumerableUnderlyingType);
+                return ConvertMultiple(
+                    memberSchema,
+                    rawValues,
+                    memberSchema.Property.Type,
+                    enumerableUnderlyingType
+                );
             }
 
             // Scalar
             if (rawValues.Count <= 1)
             {
-                return ConvertSingle(memberSchema, rawValues.SingleOrDefault(), targetType);
+                return ConvertSingle(
+                    memberSchema,
+                    rawValues.SingleOrDefault(),
+                    memberSchema.Property.Type
+                );
             }
         }
         catch (Exception ex) when (ex is not CliFxException) // don't wrap CliFxException
         {
             // We use reflection-based invocation which can throw TargetInvocationException.
-            // Unwrap these exceptions to provide a more user-friendly error message.
+            // Unwrap those exceptions to provide a more user-friendly error message.
             var errorMessage = ex is TargetInvocationException invokeEx
                 ? invokeEx.InnerException?.Message ?? invokeEx.Message
                 : ex.Message;
 
             throw CliFxException.UserError(
-                $"{memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} cannot be set from provided argument(s):" +
-                Environment.NewLine +
-                rawValues.Select(v => '<' + v + '>').JoinToString(" ") +
-                Environment.NewLine +
-                $"Error: {errorMessage}",
+                $"""
+                {memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} cannot be set from the provided argument(s):
+                {rawValues.Select(v => '<' + v + '>').JoinToString(" ")}
+                Error: {errorMessage}
+                """,
                 ex
             );
         }
 
         // Mismatch (scalar but too many values)
         throw CliFxException.UserError(
-            $"{memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} expects a single argument, but provided with multiple:" +
-            Environment.NewLine +
-            rawValues.Select(v => '<' + v + '>').JoinToString(" ")
+            $"""
+            {memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} expects a single argument, but provided with multiple:
+            {rawValues.Select(v => '<' + v + '>').JoinToString(" ")}
+            """
         );
     }
 
@@ -192,7 +200,7 @@ internal class CommandBinder
 
         foreach (var validatorType in memberSchema.ValidatorTypes)
         {
-            var validator = (IBindingValidator)_typeActivator.CreateInstance(validatorType);
+            var validator = _typeActivator.CreateInstance<IBindingValidator>(validatorType);
             var error = validator.Validate(convertedValue);
 
             if (error is not null)
@@ -202,11 +210,11 @@ internal class CommandBinder
         if (errors.Any())
         {
             throw CliFxException.UserError(
-                $"{memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} has been provided with an invalid value." +
-                Environment.NewLine +
-                "Error(s):" +
-                Environment.NewLine +
-                errors.Select(e => "- " + e.Message).JoinToString(Environment.NewLine)
+                $"""
+                {memberSchema.GetKind()} {memberSchema.GetFormattedIdentifier()} has been provided with an invalid value.
+                Error(s):
+                {errors.Select(e => "- " + e.Message).JoinToString(Environment.NewLine)}
+                """
             );
         }
     }
@@ -233,7 +241,7 @@ internal class CommandBinder
             if (position >= commandInput.Parameters.Count)
                 break;
 
-            // Scalar - take one input at the current position
+            // Scalar: take one input at the current position
             if (parameterSchema.Property.IsScalar())
             {
                 var parameterInput = commandInput.Parameters[position];
@@ -245,7 +253,7 @@ internal class CommandBinder
 
                 remainingParameterInputs.Remove(parameterInput);
             }
-            // Non-scalar - take all remaining inputs starting from the current position
+            // Non-scalar: take all remaining inputs starting from the current position
             else
             {
                 var parameterInputs = commandInput.Parameters.Skip(position).ToArray();
@@ -264,22 +272,20 @@ internal class CommandBinder
         if (remainingParameterInputs.Any())
         {
             throw CliFxException.UserError(
-                "Unexpected parameter(s):" +
-                Environment.NewLine +
-                remainingParameterInputs
-                    .Select(p => p.GetFormattedIdentifier())
-                    .JoinToString(" ")
+                $"""
+                Unexpected parameter(s):
+                {remainingParameterInputs.Select(p => p.GetFormattedIdentifier()).JoinToString(" ")}
+                """
             );
         }
 
         if (remainingRequiredParameterSchemas.Any())
         {
             throw CliFxException.UserError(
-                "Missing required parameter(s):" +
-                Environment.NewLine +
-                remainingRequiredParameterSchemas
-                    .Select(p => p.GetFormattedIdentifier())
-                    .JoinToString(" ")
+                $"""
+                Missing required parameter(s):
+                {remainingRequiredParameterSchemas.Select(p => p.GetFormattedIdentifier()).JoinToString(" ")}
+                """
             );
         }
     }
@@ -308,7 +314,7 @@ internal class CommandBinder
 
                 BindMember(optionSchema, commandInstance, rawValues);
 
-                // Required options require at least one value to be set
+                // Required options need at least one value to be set
                 if (rawValues.Any())
                     remainingRequiredOptionSchemas.Remove(optionSchema);
             }
@@ -321,11 +327,11 @@ internal class CommandBinder
 
                 BindMember(optionSchema, commandInstance, rawValues);
 
-                // Required options require at least one value to be set
+                // Required options need at least one value to be set
                 if (rawValues.Any())
                     remainingRequiredOptionSchemas.Remove(optionSchema);
             }
-            // No input - skip
+            // No input, skip
             else
             {
                 continue;
@@ -337,22 +343,20 @@ internal class CommandBinder
         if (remainingOptionInputs.Any())
         {
             throw CliFxException.UserError(
-                "Unrecognized option(s):" +
-                Environment.NewLine +
-                remainingOptionInputs
-                    .Select(o => o.GetFormattedIdentifier())
-                    .JoinToString(", ")
+                $"""
+                Unrecognized option(s):
+                {remainingOptionInputs.Select(o => o.GetFormattedIdentifier()).JoinToString(", ")}
+                """
             );
         }
 
         if (remainingRequiredOptionSchemas.Any())
         {
             throw CliFxException.UserError(
-                "Missing required option(s):" +
-                Environment.NewLine +
-                remainingRequiredOptionSchemas
-                    .Select(o => o.GetFormattedIdentifier())
-                    .JoinToString(", ")
+                $"""
+                Missing required option(s):
+                {remainingRequiredOptionSchemas.Select(o => o.GetFormattedIdentifier()).JoinToString(", ")}
+                """
             );
         }
     }

CliFx/Exceptions/CliFxException.cs

@@ -9,9 +9,11 @@ public partial class CliFxException : Exception
 {
     internal const int DefaultExitCode = 1;
 
-    // Regular `exception.Message` never returns null, even if
-    // it hasn't been set.
-    internal string? ActualMessage { get; }
+    // When an exception is created without a message, the base Exception class
+    // provides a default message that is not very useful.
+    // This property is used to identify whether this instance was created with
+    // a custom message, so that we can avoid printing the default message.
+    internal bool HasCustomMessage { get; }
 
     /// <summary>
     /// Returned exit code.
@@ -24,7 +26,7 @@ public partial class CliFxException : Exception
     public bool ShowHelp { get; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="CliFxException"/>.
+    /// Initializes an instance of <see cref="CliFxException" />.
     /// </summary>
     public CliFxException(
         string message,
@@ -33,7 +35,7 @@ public partial class CliFxException : Exception
         Exception? innerException = null)
         : base(message, innerException)
     {
-        ActualMessage = message;
+        HasCustomMessage = !string.IsNullOrWhiteSpace(message);
         ExitCode = exitCode;
         ShowHelp = showHelp;
     }
@@ -41,13 +43,13 @@ public partial class CliFxException : Exception
 
 public partial class CliFxException
 {
-    // Internal errors don't show help because they're meant for the developer
-    // and not the end-user of the application.
+    // Internal errors don't show help because they're meant for the developer and
+    // not the end-user of the application.
     internal static CliFxException InternalError(string message, Exception? innerException = null) =>
         new(message, DefaultExitCode, false, innerException);
 
-    // User errors are typically caused by invalid input and they're meant for
-    // the end-user, so we want to show help.
+    // User errors are typically caused by invalid input and they're meant for the end-user,
+    // so we want to show help.
     internal static CliFxException UserError(string message, Exception? innerException = null) =>
         new(message, DefaultExitCode, true, innerException);
 }

CliFx/Exceptions/CommandException.cs

@@ -9,7 +9,7 @@ namespace CliFx.Exceptions;
 public class CommandException : CliFxException
 {
     /// <summary>
-    /// Initializes an instance of <see cref="CommandException"/>.
+    /// Initializes an instance of <see cref="CommandException" />.
     /// </summary>
     public CommandException(
         string message,

CliFx/Extensibility/BindingConverter.cs

@@ -1,6 +1,6 @@
 namespace CliFx.Extensibility;
 
-// Used internally to simplify usage from reflection
+// Used internally to simplify the usage from reflection
 internal interface IBindingConverter
 {
     object? Convert(string? rawValue);
@@ -12,7 +12,7 @@ internal interface IBindingConverter
 public abstract class BindingConverter<T> : IBindingConverter
 {
     /// <summary>
-    /// Parses value from a raw command line argument.
+    /// Parses value from a raw command-line argument.
     /// </summary>
     public abstract T Convert(string? rawValue);
 

CliFx/Extensibility/BindingValidationError.cs

@@ -11,7 +11,7 @@ public class BindingValidationError
     public string Message { get; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="BindingValidationError"/>.
+    /// Initializes an instance of <see cref="BindingValidationError" />.
     /// </summary>
     public BindingValidationError(string message) => Message = message;
 }

CliFx/Extensibility/BindingValidator.cs

@@ -1,6 +1,6 @@
 namespace CliFx.Extensibility;
 
-// Used internally to simplify usage from reflection
+// Used internally to simplify the usage from reflection
 internal interface IBindingValidator
 {
     BindingValidationError? Validate(object? value);
@@ -26,7 +26,7 @@ public abstract class BindingValidator<T> : IBindingValidator
     /// Returns null if validation is successful, or an error in case of failure.
     /// </summary>
     /// <remarks>
-    /// You can use the utility methods <see cref="Ok"/> and <see cref="Error"/> to
+    /// You can use the utility methods <see cref="Ok" /> and <see cref="Error" /> to
     /// create an appropriate result.
     /// </remarks>
     public abstract BindingValidationError? Validate(T? value);

CliFx/Formatting/CommandInputConsoleFormatter.cs

@@ -13,7 +13,7 @@ internal class CommandInputConsoleFormatter : ConsoleFormatter
 
     private void WriteCommandLineArguments(CommandInput commandInput)
     {
-        Write("Command line:");
+        Write("Command-line:");
         WriteLine();
 
         WriteHorizontalMargin();

CliFx/Formatting/ExceptionConsoleFormatter.cs

@@ -98,26 +98,22 @@ internal class ExceptionConsoleFormatter : ConsoleFormatter
         if (!string.IsNullOrWhiteSpace(exception.StackTrace))
         {
             // Parse and pretty-print the stacktrace
-            foreach (var stackFrame in StackFrame.ParseMany(exception.StackTrace))
-            {
+            foreach (var stackFrame in StackFrame.ParseTrace(exception.StackTrace))
                 WriteStackFrame(stackFrame, indentLevel);
-            }
         }
     }
 
     public void WriteException(Exception exception)
     {
-        // Domain exceptions should be printed with minimal information
-        // because they are meant for the user of the application,
-        // not the user of the library.
-        if (exception is CliFxException cliFxException &&
-            !string.IsNullOrWhiteSpace(cliFxException.ActualMessage))
+        // Domain exceptions should be printed with minimal information because they are
+        // meant for the user of the application, not the user of the library.
+        if (exception is CliFxException { HasCustomMessage: true } cliFxException)
         {
-            Write(ConsoleColor.Red, cliFxException.ActualMessage);
+            Write(ConsoleColor.Red, cliFxException.Message);
             WriteLine();
         }
-        // All other exceptions most likely indicate an actual bug
-        // and should include stacktrace and other detailed information.
+        // All other exceptions most likely indicate an actual bug and should include
+        // the stacktrace and other detailed information.
         else
         {
             Write(ConsoleColor.White, ConsoleColor.DarkRed, "ERROR");

CliFx/Formatting/HelpConsoleFormatter.cs

@@ -206,7 +206,7 @@ internal class HelpConsoleFormatter : ConsoleFormatter
                 Write('.');
                 Write(' ');
             }
-            
+
             // Default value
             if (!parameterSchema.IsRequired)
             {
@@ -367,7 +367,9 @@ internal class HelpConsoleFormatter : ConsoleFormatter
     {
         var childCommandSchemas = _context
             .ApplicationSchema
-            .GetChildCommands(_context.CommandSchema.Name);
+            .GetChildCommands(_context.CommandSchema.Name)
+            .OrderBy(a => a.Name, StringComparer.Ordinal)
+            .ToArray();
 
         if (!childCommandSchemas.Any())
             return;
@@ -402,14 +404,15 @@ internal class HelpConsoleFormatter : ConsoleFormatter
             // Child commands of child command
             var grandChildCommandSchemas = _context
                 .ApplicationSchema
-                .GetChildCommands(childCommandSchema.Name);
+                .GetChildCommands(childCommandSchema.Name)
+                .OrderBy(c => c.Name, StringComparer.Ordinal)
+                .ToArray();
 
             if (grandChildCommandSchemas.Any())
             {
                 Write(ConsoleColor.White, "Subcommands: ");
 
                 var isFirst = true;
-
                 foreach (var grandChildCommandSchema in grandChildCommandSchemas)
                 {
                     if (isFirst)

CliFx/ICommand.cs

@@ -4,16 +4,16 @@ using CliFx.Infrastructure;
 namespace CliFx;
 
 /// <summary>
-/// Entry point through which the user interacts with the command line application.
+/// Entry point through which the user interacts with the command-line application.
 /// </summary>
 public interface ICommand
 {
     /// <summary>
-    /// Executes the command using the specified implementation of <see cref="IConsole"/>.
+    /// Executes the command using the specified implementation of <see cref="IConsole" />.
     /// </summary>
     /// <remarks>
     /// If the execution of the command is not asynchronous, simply end the method with
-    /// <code>return default;</code>
+    /// <c>return default;</c>
     /// </remarks>
     ValueTask ExecuteAsync(IConsole console);
 }

CliFx/Infrastructure/ConsoleReader.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 namespace CliFx.Infrastructure;
 
 /// <summary>
-/// Implements a <see cref="TextReader"/> for reading characters from a console stream.
+/// Implements a <see cref="TextReader" /> for reading characters from a console stream.
 /// </summary>
 // Both the underlying stream AND the stream reader must be synchronized!
 // https://github.com/Tyrrrz/CliFx/issues/123
@@ -19,7 +19,7 @@ public partial class ConsoleReader : StreamReader
     public IConsole Console { get; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="ConsoleReader"/>.
+    /// Initializes an instance of <see cref="ConsoleReader" />.
     /// </summary>
     public ConsoleReader(IConsole console, Stream stream, Encoding encoding)
         : base(stream, encoding, false, 4096)
@@ -28,7 +28,7 @@ public partial class ConsoleReader : StreamReader
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="ConsoleReader"/>.
+    /// Initializes an instance of <see cref="ConsoleReader" />.
     /// </summary>
     public ConsoleReader(IConsole console, Stream stream)
         : this(console, stream, System.Console.InputEncoding)

CliFx/Infrastructure/ConsoleWriter.cs

@@ -8,7 +8,7 @@ using CliFx.Utils;
 namespace CliFx.Infrastructure;
 
 /// <summary>
-/// Implements a <see cref="TextWriter"/> for writing characters to a console stream.
+/// Implements a <see cref="TextWriter" /> for writing characters to a console stream.
 /// </summary>
 // Both the underlying stream AND the stream writer must be synchronized!
 // https://github.com/Tyrrrz/CliFx/issues/123
@@ -20,7 +20,7 @@ public partial class ConsoleWriter : StreamWriter
     public IConsole Console { get; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="ConsoleWriter"/>.
+    /// Initializes an instance of <see cref="ConsoleWriter" />.
     /// </summary>
     public ConsoleWriter(IConsole console, Stream stream, Encoding encoding)
         : base(stream, encoding.WithoutPreamble(), 256)
@@ -29,7 +29,7 @@ public partial class ConsoleWriter : StreamWriter
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="ConsoleWriter"/>.
+    /// Initializes an instance of <see cref="ConsoleWriter" />.
     /// </summary>
     public ConsoleWriter(IConsole console, Stream stream)
         : this(console, stream, System.Console.OutputEncoding)

CliFx/Infrastructure/DefaultTypeActivator.cs

@@ -4,7 +4,7 @@ using CliFx.Exceptions;
 namespace CliFx.Infrastructure;
 
 /// <summary>
-/// Implementation of <see cref="ITypeActivator"/> that instantiates an object
+/// Implementation of <see cref="ITypeActivator" /> that instantiates an object
 /// by using its parameterless constructor.
 /// </summary>
 public class DefaultTypeActivator : ITypeActivator
@@ -20,11 +20,11 @@ public class DefaultTypeActivator : ITypeActivator
         catch (MemberAccessException ex)
         {
             throw CliFxException.InternalError(
-                $"Failed to create an instance of type `{type.FullName}`, could not access the constructor." +
-                Environment.NewLine +
-                "Default type activator is only capable of instantiating a type if it has a public parameterless constructor." +
-                Environment.NewLine +
-                "To fix this, either add a parameterless constructor to the type or configure a custom activator for the application.",
+                $"""
+                Failed to create an instance of type `{type.FullName}`, could not access the constructor.
+                Default type activator is only capable of instantiating a type if it has a public parameterless constructor.
+                To fix this, either add a parameterless constructor to the type or configure a custom activator for the application.
+                """,
                 ex
             );
         }

CliFx/Infrastructure/DelegateTypeActivator.cs

@@ -4,31 +4,31 @@ using CliFx.Exceptions;
 namespace CliFx.Infrastructure;
 
 /// <summary>
-/// Implementation of <see cref="ITypeActivator"/> that instantiates an object
-/// by using a predefined function.
+/// Implementation of <see cref="ITypeActivator" /> that instantiates an object by using a predefined delegate.
 /// </summary>
 public class DelegateTypeActivator : ITypeActivator
 {
-    private readonly Func<Type, object> _func;
+    private readonly Func<Type, object> _createInstance;
 
     /// <summary>
-    /// Initializes an instance of <see cref="DelegateTypeActivator"/>.
+    /// Initializes an instance of <see cref="DelegateTypeActivator" />.
     /// </summary>
-    public DelegateTypeActivator(Func<Type, object> func) => _func = func;
+    public DelegateTypeActivator(Func<Type, object> createInstance) =>
+        _createInstance = createInstance;
 
     /// <inheritdoc />
     public object CreateInstance(Type type)
     {
-        var instance = _func(type);
+        var instance = _createInstance(type);
 
         if (instance is null)
         {
             throw CliFxException.InternalError(
-                $"Failed to create an instance of type `{type.FullName}`, received <null> instead." +
-                Environment.NewLine +
-                "To fix this, ensure that the provided type activator is configured correctly, as it's not expected to return <null>." +
-                Environment.NewLine +
-                "If you are relying on a dependency container, this error may indicate that the specified type has not been registered."
+                $"""
+                Failed to create an instance of type `{type.FullName}`, received <null> instead.
+                To fix this, ensure that the provided type activator is configured correctly, as it's not expected to return <null>.
+                If you are relying on a dependency container, this error may indicate that the specified type has not been registered.
+                """
             );
         }
 

CliFx/Infrastructure/FakeConsole.cs

@@ -6,12 +6,10 @@ using System.Threading;
 namespace CliFx.Infrastructure;
 
 /// <summary>
-/// Implementation of <see cref="IConsole"/> that uses the provided fake
+/// Implementation of <see cref="IConsole" /> that uses the provided fake
 /// standard input, output, and error streams.
+/// Use this implementation in tests to verify command interactions with the console.
 /// </summary>
-/// <remarks>
-/// Use this implementation in tests to verify how a command interacts with the console.
-/// </remarks>
 public class FakeConsole : IConsole, IDisposable
 {
     private readonly CancellationTokenSource _cancellationTokenSource = new();
@@ -42,11 +40,10 @@ public class FakeConsole : IConsole, IDisposable
     public ConsoleColor BackgroundColor { get; set; } = ConsoleColor.Black;
 
     /// <inheritdoc />
-    public void ResetColor()
-    {
-        ForegroundColor = ConsoleColor.Gray;
-        BackgroundColor = ConsoleColor.Black;
-    }
+    public int WindowWidth { get; set; } = 232; // Windows defaults
+
+    /// <inheritdoc />
+    public int WindowHeight { get; set; } = 14; // Windows defaults
 
     /// <inheritdoc />
     public int CursorLeft { get; set; }
@@ -55,7 +52,7 @@ public class FakeConsole : IConsole, IDisposable
     public int CursorTop { get; set; }
 
     /// <summary>
-    /// Initializes an instance of <see cref="FakeConsole"/>.
+    /// Initializes an instance of <see cref="FakeConsole" />.
     /// </summary>
     public FakeConsole(Stream? input = null, Stream? output = null, Stream? error = null)
     {
@@ -74,10 +71,17 @@ public class FakeConsole : IConsole, IDisposable
             );
 
     /// <summary>
-    /// Enqueues a simulated key press, which can then be read by calling <see cref="ReadKey"/>.
+    /// Enqueues a simulated key press, which can then be read by calling <see cref="ReadKey" />.
     /// </summary>
     public void EnqueueKey(ConsoleKeyInfo key) => _keys.Enqueue(key);
-    
+
+    /// <inheritdoc />
+    public void ResetColor()
+    {
+        ForegroundColor = ConsoleColor.Gray;
+        BackgroundColor = ConsoleColor.Black;
+    }
+
     /// <inheritdoc />
     public void Clear()
     {
@@ -85,12 +89,12 @@ public class FakeConsole : IConsole, IDisposable
 
     /// <inheritdoc />
     public CancellationToken RegisterCancellationHandler() => _cancellationTokenSource.Token;
-    
+
     /// <summary>
     /// Sends a cancellation signal to the currently executing command.
     /// </summary>
     /// <remarks>
-    /// If the command is not cancellation-aware (i.e. it doesn't call <see cref="IConsole.RegisterCancellationHandler"/>),
+    /// If the command is not cancellation-aware (i.e. it doesn't call <see cref="IConsole.RegisterCancellationHandler" />),
     /// this method will not have any effect.
     /// </remarks>
     public void RequestCancellation(TimeSpan? delay = null)

CliFx/Infrastructure/FakeInMemoryConsole.cs

@@ -3,12 +3,10 @@
 namespace CliFx.Infrastructure;
 
 /// <summary>
-/// Implementation of <see cref="IConsole"/> that uses fake
+/// Implementation of <see cref="IConsole" /> that uses fake
 /// standard input, output, and error streams backed by in-memory stores.
+/// Use this implementation in tests to verify command interactions with the console.
 /// </summary>
-/// <remarks>
-/// Use this implementation in tests to verify how a command interacts with the console.
-/// </remarks>
 public class FakeInMemoryConsole : FakeConsole
 {
     private readonly MemoryStream _input;
@@ -24,7 +22,7 @@ public class FakeInMemoryConsole : FakeConsole
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="FakeInMemoryConsole"/>.
+    /// Initializes an instance of <see cref="FakeInMemoryConsole" />.
     /// </summary>
     public FakeInMemoryConsole()
         : this(new MemoryStream(), new MemoryStream(), new MemoryStream())
@@ -36,17 +34,17 @@ public class FakeInMemoryConsole : FakeConsole
     /// </summary>
     public void WriteInput(byte[] data)
     {
-        // We want the consumer to be able to read what we wrote
-        // so we need to seek the stream back to its original
-        // position after we finish writing.
         lock (_input)
         {
             var lastPosition = _input.Position;
 
+            // Write the data to the end of the stream
+            _input.Seek(0, SeekOrigin.End);
             _input.Write(data);
             _input.Flush();
 
-            _input.Position = lastPosition;
+            // Reset position to where it was before
+            _input.Seek(lastPosition, SeekOrigin.Begin);
         }
     }
 

CliFx/Infrastructure/IConsole.cs

@@ -15,7 +15,7 @@ public interface IConsole
     ConsoleReader Input { get; }
 
     /// <summary>
-    /// Whether the input stream is redirected.
+    /// Gets a value that indicates whether input has been redirected from the standard input stream.
     /// </summary>
     bool IsInputRedirected { get; }
 
@@ -25,7 +25,7 @@ public interface IConsole
     ConsoleWriter Output { get; }
 
     /// <summary>
-    /// Whether the output stream is redirected.
+    /// Gets a value that indicates whether output has been redirected from the standard output stream.
     /// </summary>
     bool IsOutputRedirected { get; }
 
@@ -35,32 +35,37 @@ public interface IConsole
     ConsoleWriter Error { get; }
 
     /// <summary>
-    /// Whether the error stream is redirected.
+    /// Gets a value that indicates whether error output has been redirected from the standard error stream.
     /// </summary>
     bool IsErrorRedirected { get; }
 
     /// <summary>
-    /// Current foreground color.
+    /// Gets or sets the foreground color of the console
     /// </summary>
     ConsoleColor ForegroundColor { get; set; }
 
     /// <summary>
-    /// Current background color.
+    /// Gets or sets the background color of the console.
     /// </summary>
     ConsoleColor BackgroundColor { get; set; }
 
     /// <summary>
-    /// Resets foreground and background colors to their default values.
+    /// Gets or sets the width of the console window.
     /// </summary>
-    void ResetColor();
+    int WindowWidth { get; set; }
 
     /// <summary>
-    /// Cursor left offset.
+    /// Gets or sets the height of the console window.
+    /// </summary>
+    int WindowHeight { get; set; }
+
+    /// <summary>
+    /// Gets or sets the column position of the cursor within the buffer area.
     /// </summary>
     int CursorLeft { get; set; }
 
     /// <summary>
-    /// Cursor top offset.
+    /// Gets or sets the row position of the cursor within the buffer area.
     /// </summary>
     int CursorTop { get; set; }
 
@@ -68,39 +73,43 @@ public interface IConsole
     /// Obtains the next character or function key pressed by the user.
     /// </summary>
     ConsoleKeyInfo ReadKey(bool intercept = false);
-    
+
+    /// <summary>
+    /// Sets the foreground and background console colors to their defaults.
+    /// </summary>
+    void ResetColor();
+
     /// <summary>
     /// Clears the console buffer and corresponding console window of display information.
     /// </summary>
     void Clear();
-    
+
     /// <summary>
     /// Registers a handler for the interrupt signal (Ctrl+C) on the console and returns
-    /// a token representing the cancellation request.
+    /// the token that represents the associated cancellation request.
     /// Subsequent calls to this method have no side effects and return the same token.
     /// </summary>
     /// <remarks>
     /// <para>
-    /// Calling this method effectively makes the command cancellation-aware, which
-    /// means that sending the interrupt signal won't immediately terminate the application,
-    /// but will instead trigger a token that the command can use to exit more gracefully.
+    /// Calling this method makes the command cancellation-aware, which means that sending
+    /// the interrupt signal won't immediately terminate the application, but will instead
+    /// trigger the associated token, allowing the command to exit early but on its own terms.
     /// </para>
     /// <para>
-    /// Note that the handler is only respected when the user sends the interrupt signal for the first time.
-    /// If the user decides to issue the signal again, the application will terminate immediately
-    /// regardless of whether the command is cancellation-aware.
+    /// Note that if the user sends the interrupt signal a second time, the application will
+    /// be forcefully terminated without triggering the token.
     /// </para>
     /// </remarks>
     CancellationToken RegisterCancellationHandler();
 }
 
 /// <summary>
-/// Extensions for <see cref="IConsole"/>.
+/// Extensions for <see cref="IConsole" />.
 /// </summary>
 public static class ConsoleExtensions
 {
     /// <summary>
-    /// Sets the specified foreground color and returns an <see cref="IDisposable"/>
+    /// Sets the specified foreground color and returns an <see cref="IDisposable" />
     /// that will reset the color back to its previous value upon disposal.
     /// </summary>
     public static IDisposable WithForegroundColor(this IConsole console, ConsoleColor foregroundColor)
@@ -112,7 +121,7 @@ public static class ConsoleExtensions
     }
 
     /// <summary>
-    /// Sets the specified background color and returns an <see cref="IDisposable"/>
+    /// Sets the specified background color and returns an <see cref="IDisposable" />
     /// that will reset the color back to its previous value upon disposal.
     /// </summary>
     public static IDisposable WithBackgroundColor(this IConsole console, ConsoleColor backgroundColor)
@@ -124,7 +133,7 @@ public static class ConsoleExtensions
     }
 
     /// <summary>
-    /// Sets the specified foreground and background colors and returns an <see cref="IDisposable"/>
+    /// Sets the specified foreground and background colors and returns an <see cref="IDisposable" />
     /// that will reset the colors back to their previous values upon disposal.
     /// </summary>
     public static IDisposable WithColors(

CliFx/Infrastructure/ITypeActivator.cs

@@ -1,4 +1,7 @@
 using System;
+using CliFx.Exceptions;
+using CliFx.Extensibility;
+using CliFx.Utils.Extensions;
 
 namespace CliFx.Infrastructure;
 
@@ -11,4 +14,19 @@ public interface ITypeActivator
     /// Creates an instance of the specified type.
     /// </summary>
     object CreateInstance(Type type);
+}
+
+internal static class TypeActivatorExtensions
+{
+    public static T CreateInstance<T>(this ITypeActivator activator, Type type)
+    {
+        if (!typeof(T).IsAssignableFrom(type))
+        {
+            throw CliFxException.InternalError(
+                $"Type '{type.FullName}' is not assignable to '{typeof(T).FullName}'."
+            );
+        }
+
+        return (T)activator.CreateInstance(type);
+    }
 }

CliFx/Infrastructure/SystemConsole.cs

@@ -4,7 +4,7 @@ using System.Threading;
 namespace CliFx.Infrastructure;
 
 /// <summary>
-/// Implementation of <see cref="IConsole"/> that represents the real system console.
+/// Implementation of <see cref="IConsole" /> that represents the real system console.
 /// </summary>
 public class SystemConsole : IConsole, IDisposable
 {
@@ -41,7 +41,21 @@ public class SystemConsole : IConsole, IDisposable
         get => Console.BackgroundColor;
         set => Console.BackgroundColor = value;
     }
-    
+
+    /// <inheritdoc />
+    public int WindowWidth
+    {
+        get => Console.WindowWidth;
+        set => Console.WindowWidth = value;
+    }
+
+    /// <inheritdoc />
+    public int WindowHeight
+    {
+        get => Console.WindowHeight;
+        set => Console.WindowHeight = value;
+    }
+
     /// <inheritdoc />
     public int CursorLeft
     {
@@ -57,7 +71,7 @@ public class SystemConsole : IConsole, IDisposable
     }
 
     /// <summary>
-    /// Initializes an instance of <see cref="SystemConsole"/>.
+    /// Initializes an instance of <see cref="SystemConsole" />.
     /// </summary>
     public SystemConsole()
     {
@@ -66,15 +80,15 @@ public class SystemConsole : IConsole, IDisposable
         Error = ConsoleWriter.Create(this, Console.OpenStandardError());
     }
 
+    /// <inheritdoc />
+    public ConsoleKeyInfo ReadKey(bool intercept = false) => Console.ReadKey(intercept);
+
     /// <inheritdoc />
     public void ResetColor() => Console.ResetColor();
 
-    /// <inheritdoc />
-    public ConsoleKeyInfo ReadKey(bool intercept = false) => Console.ReadKey(intercept);
-    
     /// <inheritdoc />
     public void Clear() => Console.Clear();
-    
+
     /// <inheritdoc />
     public CancellationToken RegisterCancellationHandler()
     {
@@ -95,7 +109,7 @@ public class SystemConsole : IConsole, IDisposable
 
         return (_cancellationTokenSource = cts).Token;
     }
-    
+
     /// <inheritdoc />
     public void Dispose()
     {