Merge master

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.gitattributes

@@ -1,63 +0,0 @@
-###############################################################################
-# Set default behavior to automatically normalize line endings.
-###############################################################################
-* text=auto
-
-###############################################################################
-# Set default behavior for command prompt diff.
-#
-# This is need for earlier builds of msysgit that does not have it on by
-# default for csharp files.
-# Note: This is only used by command line
-###############################################################################
-#*.cs     diff=csharp
-
-###############################################################################
-# Set the merge driver for project and solution files
-#
-# Merging from the command prompt will add diff markers to the files if there
-# are conflicts (Merging from VS is not affected by the settings below, in VS
-# the diff markers are never inserted). Diff markers may cause the following 
-# file extensions to fail to load in VS. An alternative would be to treat
-# these files as binary and thus will always conflict and require user
-# intervention with every merge. To do so, just uncomment the entries below
-###############################################################################
-#*.sln       merge=binary
-#*.csproj    merge=binary
-#*.vbproj    merge=binary
-#*.vcxproj   merge=binary
-#*.vcproj    merge=binary
-#*.dbproj    merge=binary
-#*.fsproj    merge=binary
-#*.lsproj    merge=binary
-#*.wixproj   merge=binary
-#*.modelproj merge=binary
-#*.sqlproj   merge=binary
-#*.wwaproj   merge=binary
-
-###############################################################################
-# behavior for image files
-#
-# image files are treated as binary by default.
-###############################################################################
-#*.jpg   binary
-#*.png   binary
-#*.gif   binary
-
-###############################################################################
-# diff behavior for common document formats
-# 
-# Convert binary document formats to text before diffing them. This feature
-# is only available from the command line. Turn it on by uncommenting the 
-# entries below.
-###############################################################################
-#*.doc   diff=astextplain
-#*.DOC   diff=astextplain
-#*.docx  diff=astextplain
-#*.DOCX  diff=astextplain
-#*.dot   diff=astextplain
-#*.DOT   diff=astextplain
-#*.pdf   diff=astextplain
-#*.PDF   diff=astextplain
-#*.rtf   diff=astextplain
-#*.RTF   diff=astextplain

.github/FUNDING.yml

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

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -0,0 +1,77 @@
+name: 🐛 Bug report
+description: Report broken functionality.
+labels: [bug]
+
+body:
+  - type: markdown
+    attributes:
+      value: |
+        - Avoid generic or vague titles such as "Something's not working" or "A couple of problems" — be as descriptive as possible.
+        - Keep your issue focused on one single problem. If you have multiple bug reports, please create a separate issue for each of them.
+        - Issues should represent **complete and actionable** work items. If you are unsure about something or have a question, please start a [discussion](https://github.com/Tyrrrz/CliFx/discussions/new) instead.
+        - Remember that **CliFx** is an open-source project funded by the community. If you find it useful, **please consider [donating](https://tyrrrz.me/donate) to support its development**.
+
+        ___
+
+  - type: input
+    attributes:
+      label: Version
+      description: Which version of the package does this bug affect? Make sure you're not using an outdated version.
+      placeholder: v1.0.0
+    validations:
+      required: true
+
+  - type: input
+    attributes:
+      label: Platform
+      description: Which platform do you experience this bug on?
+      placeholder: .NET 7.0 / Windows 11
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Steps to reproduce
+      description: >
+        Minimum steps required to reproduce the bug, including prerequisites, code snippets, or other relevant items.
+        The information provided in this field must be readily actionable, meaning that anyone should be able to reproduce the bug by following these steps.
+        If the reproduction steps are too complex to fit in this field, please provide a link to a repository instead.
+      placeholder: |
+        - Step 1
+        - Step 2
+        - Step 3
+    validations:
+      required: true
+
+  - type: textarea
+    attributes:
+      label: Details
+      description: Clear and thorough explanation of the bug, including any additional information you may find relevant.
+      placeholder: |
+        - Expected behavior: ...
+        - Actual behavior: ...
+    validations:
+      required: true
+
+  - type: checkboxes
+    attributes:
+      label: Checklist
+      description: Quick list of checks to ensure that everything is in order.
+      options:
+        - label: I have looked through existing issues to make sure that this bug has not been reported before
+          required: true
+        - label: I have provided a descriptive title for this issue
+          required: true
+        - label: I have made sure that this bug is reproducible on the latest version of the package
+          required: true
+        - label: I have provided all the information needed to reproduce this bug as efficiently as possible
+          required: true
+        - label: I have sponsored this project
+          required: false
+        - label: I have not read any of the above and just checked all the boxes to submit the issue
+          required: false
+
+  - type: markdown
+    attributes:
+      value: |
+        If you are struggling to provide actionable reproduction steps, or if something else is preventing you from creating a complete bug report, please start a [discussion](https://github.com/Tyrrrz/CliFx/discussions/new) instead.

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,11 @@
+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: 🗨 Discussions
+    url: https://github.com/Tyrrrz/CliFx/discussions/new
+    about: Ask and answer questions.
+  - name: 💬 Discord server
+    url: https://discord.gg/2SUWKFnHSm
+    about: Chat with the project community.

.github/dependabot.yml

@@ -0,0 +1,22 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: monthly
+    labels:
+      - enhancement
+    groups:
+      actions:
+        patterns:
+          - "*"
+  - package-ecosystem: nuget
+    directory: "/"
+    schedule:
+      interval: monthly
+    labels:
+      - enhancement
+    groups:
+      nuget:
+        patterns:
+          - "*"

.github/workflows/CD.yml

@@ -1,25 +0,0 @@
-name: CD
-
-on:
-  push:
-    tags:
-    - '*'
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v2
-
-    - name: Install .NET Core
-      uses: actions/setup-dotnet@v1.4.0
-      with:
-        dotnet-version: 3.1.100
-
-    - name: Pack
-      run: dotnet pack CliFx --configuration Release
-
-    - name: Deploy
-      run: dotnet nuget push CliFx/bin/Release/*.nupkg -s nuget.org -k ${{secrets.NUGET_TOKEN}}

.github/workflows/CI.yml

@@ -1,29 +0,0 @@
-name: CI
-
-on: [push, pull_request]
-
-jobs:
-  build:
-    runs-on: ${{ matrix.os }}
-
-    strategy:
-      matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest]
-
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v2
-
-    - name: Install .NET Core
-      uses: actions/setup-dotnet@v1.4.0
-      with:
-        dotnet-version: 3.1.100
-
-    - name: Build & test
-      run: dotnet test --configuration Release
-
-    - name: Upload coverage
-      uses: codecov/codecov-action@v1.0.5
-      with:
-        token: ${{ secrets.CODECOV_TOKEN }}
-        file: CliFx.Tests/bin/Release/Coverage.xml

.github/workflows/main.yml

@@ -0,0 +1,34 @@
+name: main
+
+on:
+  workflow_dispatch:
+    inputs:
+      package-version:
+        type: string
+        description: Package version
+        required: false
+      deploy:
+        type: boolean
+        description: Deploy package
+        required: false
+        default: false
+  push:
+    branches:
+      - master
+    tags:
+      - "*"
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  main:
+    uses: Tyrrrz/.github/.github/workflows/nuget.yml@master
+    with:
+      deploy: ${{ inputs.deploy || github.ref_type == 'tag' }}
+      package-version: ${{ inputs.package-version || (github.ref_type == 'tag' && github.ref_name) || format('0.0.0-ci-{0}', github.sha) }}
+      dotnet-version: 9.0.x
+    secrets:
+      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+      NUGET_TOKEN: ${{ secrets.NUGET_TOKEN }}
+      DISCORD_WEBHOOK: ${{ secrets.DISCORD_WEBHOOK }}

.gitignore

@@ -1,341 +1,12 @@
-## Ignore Visual Studio temporary files, build results, and
-## files generated by popular Visual Studio add-ons.
-##
-## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore
-
 # User-specific files
-*.rsuser
+.vs/
+.idea/
 *.suo
 *.user
-*.userosscache
-*.sln.docstates
-
-# User-specific files (MonoDevelop/Xamarin Studio)
-*.userprefs
 
 # Build results
-[Dd]ebug/
+bin/
-[Dd]ebugPublic/
+obj/
-[Rr]elease/
-[Rr]eleases/
-x64/
-x86/
-[Aa][Rr][Mm]/
-[Aa][Rr][Mm]64/
-bld/
-[Bb]in/
-[Oo]bj/
-[Ll]og/
 
-# Visual Studio 2015/2017 cache/options directory
+# Test results
-.vs/
+TestResults/
-# Uncomment if you have tasks that create the project's static files in wwwroot
-#wwwroot/
-
-# Visual Studio 2017 auto generated files
-Generated\ Files/
-
-# MSTest test Results
-[Tt]est[Rr]esult*/
-[Bb]uild[Ll]og.*
-
-# NUNIT
-*.VisualState.xml
-TestResult.xml
-
-# Build Results of an ATL Project
-[Dd]ebugPS/
-[Rr]eleasePS/
-dlldata.c
-
-# Benchmark Results
-BenchmarkDotNet.Artifacts/
-
-# .NET Core
-project.lock.json
-project.fragment.lock.json
-artifacts/
-
-# StyleCop
-StyleCopReport.xml
-
-# Files built by Visual Studio
-*_i.c
-*_p.c
-*_h.h
-*.ilk
-*.meta
-*.obj
-*.iobj
-*.pch
-*.pdb
-*.ipdb
-*.pgc
-*.pgd
-*.rsp
-*.sbr
-*.tlb
-*.tli
-*.tlh
-*.tmp
-*.tmp_proj
-*_wpftmp.csproj
-*.log
-*.vspscc
-*.vssscc
-.builds
-*.pidb
-*.svclog
-*.scc
-
-# Chutzpah Test files
-_Chutzpah*
-
-# Visual C++ cache files
-ipch/
-*.aps
-*.ncb
-*.opendb
-*.opensdf
-*.sdf
-*.cachefile
-*.VC.db
-*.VC.VC.opendb
-
-# Visual Studio profiler
-*.psess
-*.vsp
-*.vspx
-*.sap
-
-# Visual Studio Trace Files
-*.e2e
-
-# TFS 2012 Local Workspace
-$tf/
-
-# Guidance Automation Toolkit
-*.gpState
-
-# ReSharper is a .NET coding add-in
-_ReSharper*/
-*.[Rr]e[Ss]harper
-*.DotSettings.user
-
-# JustCode is a .NET coding add-in
-.JustCode
-
-# TeamCity is a build add-in
-_TeamCity*
-
-# DotCover is a Code Coverage Tool
-*.dotCover
-
-# AxoCover is a Code Coverage Tool
-.axoCover/*
-!.axoCover/settings.json
-
-# Visual Studio code coverage results
-*.coverage
-*.coveragexml
-
-# NCrunch
-_NCrunch_*
-.*crunch*.local.xml
-nCrunchTemp_*
-.ncrunchsolution
-
-# MightyMoose
-*.mm.*
-AutoTest.Net/
-
-# Web workbench (sass)
-.sass-cache/
-
-# Installshield output folder
-[Ee]xpress/
-
-# DocProject is a documentation generator add-in
-DocProject/buildhelp/
-DocProject/Help/*.HxT
-DocProject/Help/*.HxC
-DocProject/Help/*.hhc
-DocProject/Help/*.hhk
-DocProject/Help/*.hhp
-DocProject/Help/Html2
-DocProject/Help/html
-
-# Click-Once directory
-publish/
-
-# Publish Web Output
-*.[Pp]ublish.xml
-*.azurePubxml
-# Note: Comment the next line if you want to checkin your web deploy settings,
-# but database connection strings (with potential passwords) will be unencrypted
-*.pubxml
-*.publishproj
-
-# Microsoft Azure Web App publish settings. Comment the next line if you want to
-# checkin your Azure Web App publish settings, but sensitive information contained
-# in these scripts will be unencrypted
-PublishScripts/
-
-# NuGet Packages
-*.nupkg
-# The packages folder can be ignored because of Package Restore
-**/[Pp]ackages/*
-# except build/, which is used as an MSBuild target.
-!**/[Pp]ackages/build/
-# Uncomment if necessary however generally it will be regenerated when needed
-#!**/[Pp]ackages/repositories.config
-# NuGet v3's project.json files produces more ignorable files
-*.nuget.props
-*.nuget.targets
-
-# Microsoft Azure Build Output
-csx/
-*.build.csdef
-
-# Microsoft Azure Emulator
-ecf/
-rcf/
-
-# Windows Store app package directories and files
-AppPackages/
-BundleArtifacts/
-Package.StoreAssociation.xml
-_pkginfo.txt
-*.appx
-
-# Visual Studio cache files
-# files ending in .cache can be ignored
-*.[Cc]ache
-# but keep track of directories ending in .cache
-!?*.[Cc]ache/
-
-# Others
-ClientBin/
-~$*
-*~
-*.dbmdl
-*.dbproj.schemaview
-*.jfm
-*.pfx
-*.publishsettings
-orleans.codegen.cs
-
-# Including strong name files can present a security risk
-# (https://github.com/github/gitignore/pull/2483#issue-259490424)
-#*.snk
-
-# Since there are multiple workflows, uncomment next line to ignore bower_components
-# (https://github.com/github/gitignore/pull/1529#issuecomment-104372622)
-#bower_components/
-
-# RIA/Silverlight projects
-Generated_Code/
-
-# Backup & report files from converting an old project file
-# to a newer Visual Studio version. Backup files are not needed,
-# because we have git ;-)
-_UpgradeReport_Files/
-Backup*/
-UpgradeLog*.XML
-UpgradeLog*.htm
-ServiceFabricBackup/
-*.rptproj.bak
-
-# SQL Server files
-*.mdf
-*.ldf
-*.ndf
-
-# Business Intelligence projects
-*.rdl.data
-*.bim.layout
-*.bim_*.settings
-*.rptproj.rsuser
-*- Backup*.rdl
-
-# Microsoft Fakes
-FakesAssemblies/
-
-# GhostDoc plugin setting file
-*.GhostDoc.xml
-
-# Node.js Tools for Visual Studio
-.ntvs_analysis.dat
-node_modules/
-
-# Visual Studio 6 build log
-*.plg
-
-# Visual Studio 6 workspace options file
-*.opt
-
-# Visual Studio 6 auto-generated workspace file (contains which files were open etc.)
-*.vbw
-
-# Visual Studio LightSwitch build output
-**/*.HTMLClient/GeneratedArtifacts
-**/*.DesktopClient/GeneratedArtifacts
-**/*.DesktopClient/ModelManifest.xml
-**/*.Server/GeneratedArtifacts
-**/*.Server/ModelManifest.xml
-_Pvt_Extensions
-
-# Paket dependency manager
-.paket/paket.exe
-paket-files/
-
-# FAKE - F# Make
-.fake/
-
-# JetBrains Rider
-.idea/
-*.sln.iml
-
-# CodeRush personal settings
-.cr/personal
-
-# Python Tools for Visual Studio (PTVS)
-__pycache__/
-*.pyc
-
-# Cake - Uncomment if you are using it
-# tools/**
-# !tools/packages.config
-
-# Tabs Studio
-*.tss
-
-# Telerik's JustMock configuration file
-*.jmconfig
-
-# BizTalk build output
-*.btp.cs
-*.btm.cs
-*.odx.cs
-*.xsd.cs
-
-# OpenCover UI analysis results
-OpenCover/
-
-# Azure Stream Analytics local run output
-ASALocalRun/
-
-# MSBuild Binary and Structured Log
-*.binlog
-
-# NVidia Nsight GPU debugger configuration file
-*.nvuser
-
-# MFractors (Xamarin productivity tool) working folder
-.mfractor/
-
-# Local History for Visual Studio
-.localhistory/
-
-# BeatPulse healthcheck temp database
-healthchecksdb

Changelog.md

@@ -1,5 +0,0 @@
-### 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.
-- Changed argument binding behavior so that options can be set to multiple argument values while specifying them with mixed naming. For example, `--option value1 -o value2 --option value3` would result in the option being set to corresponding three values, assuming `--option` and `-o` match with the same option.

CliFx.Benchmarks/Benchmarks.CliFx.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using BenchmarkDotNet.Attributes;
+using CliFx.Attributes;
+using CliFx.Infrastructure;
+
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
+{
+    [Command]
+    public class CliFxCommand : ICommand
+    {
+        [CommandOption("str", 's')]
+        public string? StrOption { get; set; }
+
+        [CommandOption("int", 'i')]
+        public int IntOption { get; set; }
+
+        [CommandOption("bool", 'b')]
+        public bool BoolOption { get; set; }
+
+        public ValueTask ExecuteAsync(IConsole console) => default;
+    }
+
+    [Benchmark(Description = "CliFx", Baseline = true)]
+    public async ValueTask<int> ExecuteWithCliFx() =>
+        await new CliApplicationBuilder()
+            .AddCommand<CliFxCommand>()
+            .Build()
+            .RunAsync(Arguments, new Dictionary<string, string>());
+}

CliFx.Benchmarks/Benchmarks.Clipr.cs

@@ -1,6 +1,9 @@
-using clipr;
+using BenchmarkDotNet.Attributes;
+using clipr;
 
-namespace CliFx.Benchmarks.Commands
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
     public class CliprCommand
     {
@@ -13,8 +16,9 @@ namespace CliFx.Benchmarks.Commands
         [NamedArgument('b', "bool", Constraint = NumArgsConstraint.Optional, Const = true)]
         public bool BoolOption { get; set; }
 
-        public void Execute()
+        public void Execute() { }
-        {
-        }
     }
+
+    [Benchmark(Description = "Clipr")]
+    public void ExecuteWithClipr() => CliParser.Parse<CliprCommand>(Arguments).Execute();
 }

CliFx.Benchmarks/Benchmarks.Cocona.cs

@@ -0,0 +1,19 @@
+using BenchmarkDotNet.Attributes;
+using Cocona;
+
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
+{
+    public class CoconaCommand
+    {
+        public void Execute(
+            [Option("str", ['s'])] string? strOption,
+            [Option("int", ['i'])] int intOption,
+            [Option("bool", ['b'])] bool boolOption
+        ) { }
+    }
+
+    [Benchmark(Description = "Cocona")]
+    public void ExecuteWithCocona() => CoconaApp.Run<CoconaCommand>(Arguments);
+}

CliFx.Benchmarks/Benchmarks.CommandLineParser.cs

@@ -0,0 +1,27 @@
+using BenchmarkDotNet.Attributes;
+using CommandLine;
+
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
+{
+    public class CommandLineParserCommand
+    {
+        [Option('s', "str")]
+        public string? StrOption { get; set; }
+
+        [Option('i', "int")]
+        public int IntOption { get; set; }
+
+        [Option('b', "bool")]
+        public bool BoolOption { get; set; }
+
+        public void Execute() { }
+    }
+
+    [Benchmark(Description = "CommandLineParser")]
+    public void ExecuteWithCommandLineParser() =>
+        new Parser()
+            .ParseArguments(Arguments, typeof(CommandLineParserCommand))
+            .WithParsed<CommandLineParserCommand>(c => c.Execute());
+}

CliFx.Benchmarks/Benchmarks.McMaster.cs

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

CliFx.Benchmarks/Benchmarks.PowerArgs.cs

@@ -1,6 +1,9 @@
-using PowerArgs;
+using BenchmarkDotNet.Attributes;
+using PowerArgs;
 
-namespace CliFx.Benchmarks.Commands
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
 {
     public class PowerArgsCommand
     {
@@ -13,8 +16,9 @@ namespace CliFx.Benchmarks.Commands
         [ArgShortcut("--bool"), ArgShortcut("-b")]
         public bool BoolOption { get; set; }
 
-        public void Main()
+        public void Main() { }
-        {
-        }
     }
+
+    [Benchmark(Description = "PowerArgs")]
+    public void ExecuteWithPowerArgs() => Args.InvokeMain<PowerArgsCommand>(Arguments);
 }

CliFx.Benchmarks/Benchmarks.SystemCommandLine.cs

@@ -0,0 +1,33 @@
+using System.CommandLine;
+using System.Threading.Tasks;
+using BenchmarkDotNet.Attributes;
+
+namespace CliFx.Benchmarks;
+
+public partial class Benchmarks
+{
+    public class SystemCommandLineCommand
+    {
+        public static void ExecuteHandler(string s, int i, bool b) { }
+
+        public Task<int> ExecuteAsync(string[] args)
+        {
+            var stringOption = new Option<string>(["--str", "-s"]);
+            var intOption = new Option<int>(["--int", "-i"]);
+            var boolOption = new Option<bool>(["--bool", "-b"]);
+
+            var command = new RootCommand();
+            command.AddOption(stringOption);
+            command.AddOption(intOption);
+            command.AddOption(boolOption);
+
+            command.SetHandler(ExecuteHandler, stringOption, intOption, boolOption);
+
+            return command.InvokeAsync(args);
+        }
+    }
+
+    [Benchmark(Description = "System.CommandLine")]
+    public async Task<int> ExecuteWithSystemCommandLine() =>
+        await new SystemCommandLineCommand().ExecuteAsync(Arguments);
+}

CliFx.Benchmarks/Benchmarks.cs

@@ -1,52 +1,18 @@
-using System.Collections.Generic;
+using BenchmarkDotNet.Attributes;
-using System.Threading.Tasks;
-using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Configs;
 using BenchmarkDotNet.Order;
 using BenchmarkDotNet.Running;
-using CliFx.Benchmarks.Commands;
-using CommandLine;
 
-namespace CliFx.Benchmarks
+namespace CliFx.Benchmarks;
+
+[RankColumn]
+[Orderer(SummaryOrderPolicy.FastestToSlowest)]
+public partial class Benchmarks
 {
-    [SimpleJob]
+    private static readonly string[] Arguments = ["--str", "hello world", "-i", "13", "-b"];
-    [RankColumn]
-    [Orderer(SummaryOrderPolicy.FastestToSlowest)]
-    public class Benchmarks
-    {
-        private static readonly string[] Arguments = {"--str", "hello world", "-i", "13", "-b"};
-
-        [Benchmark(Description = "CliFx", Baseline = true)]
-        public async ValueTask<int> ExecuteWithCliFx() =>
-            await new CliApplicationBuilder().AddCommand(typeof(CliFxCommand)).Build().RunAsync(Arguments, new Dictionary<string, string>());
-
-        [Benchmark(Description = "System.CommandLine")]
-        public async Task<int> ExecuteWithSystemCommandLine() =>
-            await new SystemCommandLineCommand().ExecuteAsync(Arguments);
-
-        [Benchmark(Description = "McMaster.Extensions.CommandLineUtils")]
-        public int ExecuteWithMcMaster() =>
-            McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute<McMasterCommand>(Arguments);
-
-        [Benchmark(Description = "CommandLineParser")]
-        public void ExecuteWithCommandLineParser() =>
-            new Parser()
-                .ParseArguments(Arguments, typeof(CommandLineParserCommand))
-                .WithParsed<CommandLineParserCommand>(c => c.Execute());
-
-        [Benchmark(Description = "PowerArgs")]
-        public void ExecuteWithPowerArgs() =>
-            PowerArgs.Args.InvokeMain<PowerArgsCommand>(Arguments);
-
-        [Benchmark(Description = "Clipr")]
-        public void ExecuteWithClipr() =>
-            clipr.CliParser.Parse<CliprCommand>(Arguments).Execute();
-
-        [Benchmark(Description = "Cocona")]
-        public void ExecuteWithCocona() =>
-            Cocona.CoconaApp.Run<CoconaCommand>(Arguments);
 
     public static void Main() =>
-            BenchmarkRunner.Run<Benchmarks>(DefaultConfig.Instance.With(ConfigOptions.DisableOptimizationsValidator));
+        BenchmarkRunner.Run<Benchmarks>(
-    }
+            DefaultConfig.Instance.WithOptions(ConfigOptions.DisableOptimizationsValidator)
+        );
 }

CliFx.Benchmarks/CliFx.Benchmarks.csproj

@@ -1,19 +1,20 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
+    <NuGetAudit>false</NuGetAudit>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.12.0" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.14.0" />
     <PackageReference Include="clipr" Version="1.6.1" />
-    <PackageReference Include="Cocona" Version="1.3.0" />
+    <PackageReference Include="Cocona" Version="2.2.0" />
-    <PackageReference Include="CommandLineParser" Version="2.7.82" />
+    <PackageReference Include="CommandLineParser" Version="2.9.1" />
-    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="2.6.0" />
+    <PackageReference Include="CSharpier.MsBuild" Version="0.30.6" PrivateAssets="all" />
-    <PackageReference Include="PowerArgs" Version="3.6.0" />
+    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="4.1.1" />
-    <PackageReference Include="System.CommandLine.Experimental" Version="0.3.0-alpha.19317.1" />
+    <PackageReference Include="PowerArgs" Version="4.0.3" />
+    <PackageReference Include="System.CommandLine" Version="2.0.0-beta4.22272.1" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Benchmarks/Commands/CliFxCommand.cs

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

CliFx.Benchmarks/Commands/CoconaCommand.cs

@@ -1,17 +0,0 @@
-using Cocona;
-
-namespace CliFx.Benchmarks.Commands
-{
-    public class CoconaCommand
-    {
-        public void Execute(
-            [Option("str", new []{'s'})]
-            string? strOption,
-            [Option("int", new []{'i'})]
-            int intOption,
-            [Option("bool", new []{'b'})]
-            bool boolOption)
-        {
-        }
-    }
-}

CliFx.Benchmarks/Commands/CommandLineParserCommand.cs

@@ -1,20 +0,0 @@
-using CommandLine;
-
-namespace CliFx.Benchmarks.Commands
-{
-    public class CommandLineParserCommand
-    {
-        [Option('s', "str")]
-        public string? StrOption { get; set; }
-
-        [Option('i', "int")]
-        public int IntOption { get; set; }
-
-        [Option('b', "bool")]
-        public bool BoolOption { get; set; }
-
-        public void Execute()
-        {
-        }
-    }
-}

CliFx.Benchmarks/Commands/McMasterCommand.cs

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

CliFx.Benchmarks/Commands/SystemCommandLineCommand.cs

@@ -1,34 +0,0 @@
-using System.CommandLine;
-using System.CommandLine.Invocation;
-using System.Threading.Tasks;
-
-namespace CliFx.Benchmarks.Commands
-{
-    public class SystemCommandLineCommand
-    {
-        public static int ExecuteHandler(string s, int i, bool b) => 0;
-
-        public Task<int> ExecuteAsync(string[] args)
-        {
-            var command = new RootCommand
-            {
-                new Option(new[] {"--str", "-s"})
-                {
-                    Argument = new Argument<string?>()
-                },
-                new Option(new[] {"--int", "-i"})
-                {
-                    Argument = new Argument<int>()
-                },
-                new Option(new[] {"--bool", "-b"})
-                {
-                    Argument = new Argument<bool>()
-                }
-            };
-
-            command.Handler = CommandHandler.Create(typeof(SystemCommandLineCommand).GetMethod(nameof(ExecuteHandler)));
-
-            return command.InvokeAsync(args);
-        }
-    }
-}

CliFx.Benchmarks/Readme.md

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

CliFx.Demo/CliFx.Demo.csproj

@@ -1,18 +1,20 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
+    <ApplicationIcon>../favicon.ico</ApplicationIcon>
+    <PublishAot>true</PublishAot>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="3.1.1" />
+    <PackageReference Include="CSharpier.MsBuild" Version="0.30.6" PrivateAssets="all" />
-    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="9.0.1" />
   </ItemGroup>
 
   <ItemGroup>
     <ProjectReference Include="..\CliFx\CliFx.csproj" />
+    <ProjectReference Include="..\CliFx.SourceGeneration\CliFx.SourceGeneration.csproj" ReferenceOutputAssembly="false" OutputItemType="analyzer" />
   </ItemGroup>
 
 </Project>

CliFx.Demo/Commands/BookAddCommand.cs

@@ -1,68 +1,55 @@
 using System;
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Internal;
+using CliFx.Demo.Domain;
-using CliFx.Demo.Models;
+using CliFx.Demo.Utils;
-using CliFx.Demo.Services;
 using CliFx.Exceptions;
+using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book add", Description = "Adds a book to the library.")]
+public class BookAddCommand(LibraryProvider libraryProvider) : ICommand
 {
-    [Command("book add", Description = "Add a book to the library.")]
-    public partial class BookAddCommand : ICommand
-    {
-        private readonly LibraryService _libraryService;
-
     [CommandParameter(0, Name = "title", Description = "Book title.")]
-        public string Title { get; set; } = "";
+    public required string Title { get; init; }
 
-        [CommandOption("author", 'a', IsRequired = true, Description = "Book author.")]
+    [CommandOption("author", 'a', Description = "Book author.")]
-        public string Author { get; set; } = "";
+    public required string Author { get; init; }
 
     [CommandOption("published", 'p', Description = "Book publish date.")]
-        public DateTimeOffset Published { get; set; } = CreateRandomDate();
+    public DateTimeOffset Published { get; init; } =
+        new(
+            Random.Shared.Next(1800, 2020),
+            Random.Shared.Next(1, 12),
+            Random.Shared.Next(1, 28),
+            Random.Shared.Next(1, 23),
+            Random.Shared.Next(1, 59),
+            Random.Shared.Next(1, 59),
+            TimeSpan.Zero
+        );
 
     [CommandOption("isbn", 'n', Description = "Book ISBN.")]
-        public Isbn Isbn { get; set; } = CreateRandomIsbn();
+    public Isbn Isbn { get; init; } =
-
+        new(
-        public BookAddCommand(LibraryService libraryService)
+            Random.Shared.Next(0, 999),
-        {
+            Random.Shared.Next(0, 99),
-            _libraryService = libraryService;
+            Random.Shared.Next(0, 99999),
-        }
+            Random.Shared.Next(0, 99),
+            Random.Shared.Next(0, 9)
+        );
 
     public ValueTask ExecuteAsync(IConsole console)
     {
-            if (_libraryService.GetBook(Title) != null)
+        if (libraryProvider.TryGetBook(Title) is not null)
-                throw new CommandException("Book already exists.", 1);
+            throw new CommandException($"Book '{Title}' already exists.", 10);
 
         var book = new Book(Title, Author, Published, Isbn);
-            _libraryService.AddBook(book);
+        libraryProvider.AddBook(book);
 
-            console.Output.WriteLine("Book added.");
+        console.WriteLine($"Book '{Title}' added.");
-            console.RenderBook(book);
+        console.WriteBook(book);
 
         return default;
     }
-    }
-
-    public partial class BookAddCommand
-    {
-        private static readonly Random Random = new Random();
-
-        private static DateTimeOffset CreateRandomDate() => new DateTimeOffset(
-            Random.Next(1800, 2020),
-            Random.Next(1, 12),
-            Random.Next(1, 28),
-            Random.Next(1, 23),
-            Random.Next(1, 59),
-            Random.Next(1, 59),
-            TimeSpan.Zero);
-
-        private static Isbn CreateRandomIsbn() => new Isbn(
-            Random.Next(0, 999),
-            Random.Next(0, 99),
-            Random.Next(0, 99999),
-            Random.Next(0, 99),
-            Random.Next(0, 9));
-    }
 }

CliFx.Demo/Commands/BookCommand.cs

@@ -1,34 +1,27 @@
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Internal;
+using CliFx.Demo.Domain;
-using CliFx.Demo.Services;
+using CliFx.Demo.Utils;
 using CliFx.Exceptions;
+using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book", Description = "Retrieves a book from the library.")]
+public class BookCommand(LibraryProvider libraryProvider) : ICommand
 {
-    [Command("book", Description = "View, list, add or remove books.")]
+    [CommandParameter(0, Name = "title", Description = "Title of the book to retrieve.")]
-    public class BookCommand : ICommand
+    public required string Title { get; init; }
-    {
-        private readonly LibraryService _libraryService;
-
-        [CommandParameter(0, Name = "title", Description = "Book title.")]
-        public string Title { get; set; } = "";
-
-        public BookCommand(LibraryService libraryService)
-        {
-            _libraryService = libraryService;
-        }
 
     public ValueTask ExecuteAsync(IConsole console)
     {
-            var book = _libraryService.GetBook(Title);
+        var book = libraryProvider.TryGetBook(Title);
 
-            if (book == null)
+        if (book is null)
-                throw new CommandException("Book not found.", 1);
+            throw new CommandException($"Book '{Title}' not found.", 10);
 
-            console.RenderBook(book);
+        console.WriteBook(book);
 
         return default;
     }
-    }
 }

CliFx.Demo/Commands/BookListCommand.cs

@@ -1,37 +1,29 @@
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Internal;
+using CliFx.Demo.Domain;
-using CliFx.Demo.Services;
+using CliFx.Demo.Utils;
+using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book list", Description = "Lists all books in the library.")]
+public class BookListCommand(LibraryProvider libraryProvider) : ICommand
 {
-    [Command("book list", Description = "List all books in the library.")]
-    public class BookListCommand : ICommand
-    {
-        private readonly LibraryService _libraryService;
-
-        public BookListCommand(LibraryService libraryService)
-        {
-            _libraryService = libraryService;
-        }
-
     public ValueTask ExecuteAsync(IConsole console)
     {
-            var library = _libraryService.GetLibrary();
+        var library = libraryProvider.GetLibrary();
 
-            var isFirst = true;
+        for (var i = 0; i < library.Books.Count; i++)
-            foreach (var book in library.Books)
         {
-                // Margin
+            // Add margin
-                if (!isFirst)
+            if (i != 0)
-                    console.Output.WriteLine();
+                console.WriteLine();
-                isFirst = false;
 
             // Render book
-                console.RenderBook(book);
+            var book = library.Books[i];
+            console.WriteBook(book);
         }
 
         return default;
     }
-    }
 }

CliFx.Demo/Commands/BookRemoveCommand.cs

@@ -1,35 +1,28 @@
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Demo.Services;
+using CliFx.Demo.Domain;
 using CliFx.Exceptions;
+using CliFx.Infrastructure;
 
-namespace CliFx.Demo.Commands
+namespace CliFx.Demo.Commands;
+
+[Command("book remove", Description = "Removes a book from the library.")]
+public class BookRemoveCommand(LibraryProvider libraryProvider) : ICommand
 {
-    [Command("book remove", Description = "Remove a book from the library.")]
+    [CommandParameter(0, Name = "title", Description = "Title of the book to remove.")]
-    public class BookRemoveCommand : ICommand
+    public required string Title { get; init; }
-    {
-        private readonly LibraryService _libraryService;
-
-        [CommandParameter(0, Name = "title", Description = "Book title.")]
-        public string Title { get; set; } = "";
-
-        public BookRemoveCommand(LibraryService libraryService)
-        {
-            _libraryService = libraryService;
-        }
 
     public ValueTask ExecuteAsync(IConsole console)
     {
-            var book = _libraryService.GetBook(Title);
+        var book = libraryProvider.TryGetBook(Title);
 
-            if (book == null)
+        if (book is null)
-                throw new CommandException("Book not found.", 1);
+            throw new CommandException($"Book '{Title}' not found.", 10);
 
-            _libraryService.RemoveBook(book);
+        libraryProvider.RemoveBook(book);
 
-            console.Output.WriteLine($"Book {Title} removed.");
+        console.WriteLine($"Book '{Title}' removed.");
 
         return default;
     }
-    }
 }

CliFx.Demo/Domain/Book.cs

@@ -0,0 +1,5 @@
+using System;
+
+namespace CliFx.Demo.Domain;
+
+public record Book(string Title, string Author, DateTimeOffset Published, Isbn Isbn);

CliFx.Demo/Domain/Isbn.cs

@@ -0,0 +1,31 @@
+using System;
+
+namespace CliFx.Demo.Domain;
+
+public partial record Isbn(
+    int EanPrefix,
+    int RegistrationGroup,
+    int Registrant,
+    int Publication,
+    int CheckDigit
+)
+{
+    public override string ToString() =>
+        $"{EanPrefix:000}-{RegistrationGroup:00}-{Registrant:00000}-{Publication:00}-{CheckDigit:0}";
+}
+
+public partial record Isbn
+{
+    public static Isbn Parse(string value, IFormatProvider formatProvider)
+    {
+        var components = value.Split('-', 5, StringSplitOptions.RemoveEmptyEntries);
+
+        return new Isbn(
+            int.Parse(components[0], formatProvider),
+            int.Parse(components[1], formatProvider),
+            int.Parse(components[2], formatProvider),
+            int.Parse(components[3], formatProvider),
+            int.Parse(components[4], formatProvider)
+        );
+    }
+}

CliFx.Demo/Domain/Library.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace CliFx.Demo.Domain;
+
+public partial record Library(IReadOnlyList<Book> Books)
+{
+    public Library WithBook(Book book)
+    {
+        var books = Books.ToList();
+        books.Add(book);
+
+        return new Library(books);
+    }
+
+    public Library WithoutBook(Book book)
+    {
+        var books = Books.Where(b => b != book).ToArray();
+
+        return new Library(books);
+    }
+}
+
+public partial record Library
+{
+    public static Library Empty { get; } = new([]);
+}

CliFx.Demo/Domain/LibraryJsonContext.cs

@@ -0,0 +1,6 @@
+using System.Text.Json.Serialization;
+
+namespace CliFx.Demo.Domain;
+
+[JsonSerializable(typeof(Library))]
+public partial class LibraryJsonContext : JsonSerializerContext;

CliFx.Demo/Domain/LibraryProvider.cs

@@ -0,0 +1,43 @@
+using System.IO;
+using System.Linq;
+using System.Text.Json;
+
+namespace CliFx.Demo.Domain;
+
+public class LibraryProvider
+{
+    private static string StorageFilePath { get; } =
+        Path.Combine(Directory.GetCurrentDirectory(), "Library.json");
+
+    private void StoreLibrary(Library library)
+    {
+        var data = JsonSerializer.Serialize(library, LibraryJsonContext.Default.Library);
+        File.WriteAllText(StorageFilePath, data);
+    }
+
+    public Library GetLibrary()
+    {
+        if (!File.Exists(StorageFilePath))
+            return Library.Empty;
+
+        var data = File.ReadAllText(StorageFilePath);
+
+        return JsonSerializer.Deserialize(data, LibraryJsonContext.Default.Library)
+            ?? Library.Empty;
+    }
+
+    public Book? TryGetBook(string title) =>
+        GetLibrary().Books.FirstOrDefault(b => b.Title == title);
+
+    public void AddBook(Book book)
+    {
+        var updatedLibrary = GetLibrary().WithBook(book);
+        StoreLibrary(updatedLibrary);
+    }
+
+    public void RemoveBook(Book book)
+    {
+        var updatedLibrary = GetLibrary().WithoutBook(book);
+        StoreLibrary(updatedLibrary);
+    }
+}

CliFx.Demo/Internal/Extensions.cs

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

CliFx.Demo/Models/Book.cs

@@ -1,23 +0,0 @@
-using System;
-
-namespace CliFx.Demo.Models
-{
-    public class Book
-    {
-        public string Title { get; }
-
-        public string Author { get; }
-
-        public DateTimeOffset Published { get; }
-
-        public Isbn Isbn { get; }
-
-        public Book(string title, string author, DateTimeOffset published, Isbn isbn)
-        {
-            Title = title;
-            Author = author;
-            Published = published;
-            Isbn = isbn;
-        }
-    }
-}

CliFx.Demo/Models/Extensions.cs

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

CliFx.Demo/Models/Isbn.cs

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

CliFx.Demo/Models/Library.cs

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

CliFx.Demo/Program.cs

@@ -1,35 +1,18 @@
-using System;
+using CliFx;
-using System.Threading.Tasks;
+using CliFx.Demo.Domain;
-using CliFx.Demo.Commands;
-using CliFx.Demo.Services;
 using Microsoft.Extensions.DependencyInjection;
 
-namespace CliFx.Demo
+// We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
-{
+var services = new ServiceCollection();
-    public static class Program
+services.AddSingleton<LibraryProvider>();
-    {
-        private static IServiceProvider GetServiceProvider()
-        {
-            // We use Microsoft.Extensions.DependencyInjection for injecting dependencies in commands
-            var services = new ServiceCollection();
 
-            // Register services
+// Register all commands as transient services
-            services.AddSingleton<LibraryService>();
+foreach (var commandType in commandTypes)
+    services.AddTransient(commandType);
 
-            // Register commands
+return await new CliApplicationBuilder()
-            services.AddTransient<BookCommand>();
+    .SetDescription("Demo application showcasing CliFx features.")
-            services.AddTransient<BookAddCommand>();
-            services.AddTransient<BookRemoveCommand>();
-            services.AddTransient<BookListCommand>();
-
-            return services.BuildServiceProvider();
-        }
-
-        public static async Task<int> Main() =>
-            await new CliApplicationBuilder()
     .AddCommandsFromThisAssembly()
-                .UseTypeActivator(GetServiceProvider().GetService)
+    .UseTypeActivator(services.BuildServiceProvider())
     .Build()
     .RunAsync();
-    }
-}

CliFx.Demo/Readme.md

@@ -1,7 +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 shows basic CliFx functionality such as command routing, argument parsing, autogenerated help text, and some other things.
+This demo project showcases basic CliFx functionality such as command routing, argument parsing, and autogenerated help text.
-
-You can get a list of available commands by running `CliFx.Demo --help`.

CliFx.Demo/Services/LibraryService.cs

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

CliFx.Demo/Utils/ConsoleExtensions.cs

@@ -0,0 +1,39 @@
+using System;
+using CliFx.Demo.Domain;
+using CliFx.Infrastructure;
+
+namespace CliFx.Demo.Utils;
+
+internal static class ConsoleExtensions
+{
+    public static void WriteBook(this ConsoleWriter writer, Book book)
+    {
+        // Title
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Title);
+
+        // Author
+        writer.Write("  ");
+        writer.Write("Author: ");
+
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Author);
+
+        // Published
+        writer.Write("  ");
+        writer.Write("Published: ");
+
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine($"{book.Published:d}");
+
+        // ISBN
+        writer.Write("  ");
+        writer.Write("ISBN: ");
+
+        using (writer.Console.WithForegroundColor(ConsoleColor.White))
+            writer.WriteLine(book.Isbn);
+    }
+
+    public static void WriteBook(this IConsole console, Book book) =>
+        console.Output.WriteBook(book);
+}

CliFx.SourceGeneration/CliFx.SourceGeneration.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
+    <GenerateDependencyFile>true</GenerateDependencyFile>
+    <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
+    <NoWarn>$(NoWarn);RS1035</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>
+    <PackageReference Include="CSharpier.MsBuild" Version="0.28.2" PrivateAssets="all" />
+    <!-- Make sure to target the lowest possible version of the compiler for wider support -->
+    <PackageReference Include="Microsoft.CodeAnalysis" Version="4.11.0" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.11.0" PrivateAssets="all" />
+    <PackageReference Include="PolyShim" Version="1.12.0" PrivateAssets="all" />
+  </ItemGroup>
+
+</Project>

CliFx.SourceGeneration/CommandSchemaGenerator.cs

@@ -0,0 +1,130 @@
+using System.Linq;
+using CliFx.SourceGeneration.SemanticModel;
+using CliFx.SourceGeneration.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace CliFx.SourceGeneration;
+
+[Generator]
+public class CommandSchemaGenerator : IIncrementalGenerator
+{
+    public void Initialize(IncrementalGeneratorInitializationContext context)
+    {
+        var values = context.SyntaxProvider.ForAttributeWithMetadataName<(
+            CommandSymbol?,
+            Diagnostic?
+        )>(
+            KnownSymbolNames.CliFxCommandAttribute,
+            (n, _) => n is TypeDeclarationSyntax,
+            (x, _) =>
+            {
+                // Predicate above ensures that these casts are safe
+                var commandTypeSyntax = (TypeDeclarationSyntax)x.TargetNode;
+                var commandTypeSymbol = (INamedTypeSymbol)x.TargetSymbol;
+
+                // Check if the target type and all its containing types are partial
+                if (
+                    commandTypeSyntax
+                        .AncestorsAndSelf()
+                        .Any(a =>
+                            a is TypeDeclarationSyntax t
+                            && !t.Modifiers.Any(m => m.IsKind(SyntaxKind.PartialKeyword))
+                        )
+                )
+                {
+                    return (
+                        null,
+                        Diagnostic.Create(
+                            DiagnosticDescriptors.CommandMustBePartial,
+                            commandTypeSyntax.Identifier.GetLocation()
+                        )
+                    );
+                }
+
+                // Check if the target type implements ICommand
+                var hasCommandInterface = commandTypeSymbol.AllInterfaces.Any(i =>
+                    i.DisplayNameMatches(KnownSymbolNames.CliFxCommandInterface)
+                );
+
+                if (!hasCommandInterface)
+                {
+                    return (
+                        null,
+                        Diagnostic.Create(
+                            DiagnosticDescriptors.CommandMustImplementInterface,
+                            commandTypeSymbol.Locations.First()
+                        )
+                    );
+                }
+
+                // Resolve the command
+                var commandAttribute = x.Attributes.First(a =>
+                    a.AttributeClass?.DisplayNameMatches(KnownSymbolNames.CliFxCommandAttribute)
+                    == true
+                );
+
+                var command = CommandSymbol.FromSymbol(commandTypeSymbol, commandAttribute);
+
+                // TODO: validate command
+
+                return (command, null);
+            }
+        );
+
+        // Report diagnostics
+        var diagnostics = values.Select((v, _) => v.Item2).WhereNotNull();
+        context.RegisterSourceOutput(diagnostics, (x, d) => x.ReportDiagnostic(d));
+
+        // Generate command schemas
+        var symbols = values.Select((v, _) => v.Item1).WhereNotNull();
+        context.RegisterSourceOutput(
+            symbols,
+            (x, c) =>
+                x.AddSource(
+                    $"{c.Type.FullyQualifiedName}.CommandSchema.Generated.cs",
+                    // lang=csharp
+                    $$"""
+                    namespace {{c.Type.Namespace}};
+
+                    partial class {{c.Type.Name}}
+                    {
+                        public static CliFx.Schema.CommandSchema<{{c.Type.FullyQualifiedName}}> Schema { get; } = {{c.GenerateSchemaInitializationCode()}};
+                    }
+                    """
+                )
+        );
+
+        // Generate extension methods
+        var symbolsCollected = symbols.Collect();
+        context.RegisterSourceOutput(
+            symbolsCollected,
+            (x, cs) =>
+                x.AddSource(
+                    "CommandSchemaExtensions.Generated.cs",
+                    // lang=csharp
+                    $$"""
+                  namespace CliFx;
+
+                  static partial class GeneratedExtensions
+                  {
+                      public static CliFx.CliApplicationBuilder AddCommandsFromThisAssembly(this CliFx.CliApplicationBuilder builder)
+                      {
+                          {{
+                              cs.Select(c => c.Type.FullyQualifiedName)
+                                  .Select(t =>
+                                      // lang=csharp
+                                      $"builder.AddCommand({t}.Schema);"
+                                  )
+                                  .JoinToString("\n")
+                          }}
+                          
+                          return builder;
+                      }
+                  }
+                  """
+                )
+        );
+    }
+}

CliFx.SourceGeneration/DiagnosticDescriptors.cs

@@ -0,0 +1,27 @@
+using CliFx.SourceGeneration.SemanticModel;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration;
+
+internal static class DiagnosticDescriptors
+{
+    public static DiagnosticDescriptor CommandMustBePartial { get; } =
+        new(
+            $"{nameof(CliFx)}_{nameof(CommandMustBePartial)}",
+            "Command types must be declared as `partial`",
+            "This type (and all its containing types, if present) must be declared as `partial` in order to be a valid command.",
+            "CliFx",
+            DiagnosticSeverity.Error,
+            true
+        );
+
+    public static DiagnosticDescriptor CommandMustImplementInterface { get; } =
+        new(
+            $"{nameof(CliFx)}_{nameof(CommandMustImplementInterface)}",
+            $"Commands must implement the `{KnownSymbolNames.CliFxCommandInterface}` interface",
+            $"This type must implement the `{KnownSymbolNames.CliFxCommandInterface}` interface in order to be a valid command.",
+            "CliFx",
+            DiagnosticSeverity.Error,
+            true
+        );
+}

CliFx.SourceGeneration/SemanticModel/CommandInputSymbol.cs

@@ -0,0 +1,66 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration.SemanticModel;
+
+internal abstract partial class CommandInputSymbol(
+    PropertyDescriptor property,
+    bool isSequence,
+    string? description,
+    TypeDescriptor? converterType,
+    IReadOnlyList<TypeDescriptor> validatorTypes
+)
+{
+    public PropertyDescriptor Property { get; } = property;
+
+    public bool IsSequence { get; } = isSequence;
+
+    public string? Description { get; } = description;
+
+    public TypeDescriptor? ConverterType { get; } = converterType;
+
+    public IReadOnlyList<TypeDescriptor> ValidatorTypes { get; } = validatorTypes;
+}
+
+internal partial class CommandInputSymbol : IEquatable<CommandInputSymbol>
+{
+    public bool Equals(CommandInputSymbol? other)
+    {
+        if (ReferenceEquals(null, other))
+            return false;
+        if (ReferenceEquals(this, other))
+            return true;
+
+        return Property.Equals(other.Property)
+            && IsSequence == other.IsSequence
+            && Description == other.Description
+            && Equals(ConverterType, other.ConverterType)
+            && ValidatorTypes.SequenceEqual(other.ValidatorTypes);
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (ReferenceEquals(null, obj))
+            return false;
+        if (ReferenceEquals(this, obj))
+            return true;
+        if (obj.GetType() != GetType())
+            return false;
+
+        return Equals((CommandInputSymbol)obj);
+    }
+
+    public override int GetHashCode() =>
+        HashCode.Combine(Property, IsSequence, Description, ConverterType, ValidatorTypes);
+}
+
+internal partial class CommandInputSymbol
+{
+    public static bool IsSequenceType(ITypeSymbol type) =>
+        type.AllInterfaces.Any(i =>
+            i.SpecialType == SpecialType.System_Collections_Generic_IEnumerable_T
+        )
+        && type.SpecialType != SpecialType.System_String;
+}

CliFx.SourceGeneration/SemanticModel/CommandOptionSymbol.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using CliFx.SourceGeneration.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration.SemanticModel;
+
+internal partial class CommandOptionSymbol(
+    PropertyDescriptor property,
+    bool isSequence,
+    string? name,
+    char? shortName,
+    string? environmentVariable,
+    bool isRequired,
+    string? description,
+    TypeDescriptor? converterType,
+    IReadOnlyList<TypeDescriptor> validatorTypes
+) : CommandInputSymbol(property, isSequence, description, converterType, validatorTypes)
+{
+    public string? Name { get; } = name;
+
+    public char? ShortName { get; } = shortName;
+
+    public string? EnvironmentVariable { get; } = environmentVariable;
+
+    public bool IsRequired { get; } = isRequired;
+}
+
+internal partial class CommandOptionSymbol : IEquatable<CommandOptionSymbol>
+{
+    public bool Equals(CommandOptionSymbol? other)
+    {
+        if (ReferenceEquals(null, other))
+            return false;
+        if (ReferenceEquals(this, other))
+            return true;
+
+        return base.Equals(other)
+            && Name == other.Name
+            && ShortName == other.ShortName
+            && EnvironmentVariable == other.EnvironmentVariable
+            && IsRequired == other.IsRequired;
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (ReferenceEquals(null, obj))
+            return false;
+        if (ReferenceEquals(this, obj))
+            return true;
+        if (obj.GetType() != GetType())
+            return false;
+
+        return Equals((CommandOptionSymbol)obj);
+    }
+
+    public override int GetHashCode() =>
+        HashCode.Combine(base.GetHashCode(), Name, ShortName, EnvironmentVariable, IsRequired);
+}
+
+internal partial class CommandOptionSymbol
+{
+    public static CommandOptionSymbol FromSymbol(
+        IPropertySymbol property,
+        AttributeData attribute
+    ) =>
+        new(
+            PropertyDescriptor.FromSymbol(property),
+            IsSequenceType(property.Type),
+            attribute
+                .ConstructorArguments.FirstOrDefault(a =>
+                    a.Type?.SpecialType == SpecialType.System_String
+                )
+                .Value as string,
+            attribute
+                .ConstructorArguments.FirstOrDefault(a =>
+                    a.Type?.SpecialType == SpecialType.System_Char
+                )
+                .Value as char?,
+            attribute.GetNamedArgumentValue("EnvironmentVariable", default(string)),
+            attribute.GetNamedArgumentValue("IsRequired", property.IsRequired),
+            attribute.GetNamedArgumentValue("Description", default(string)),
+            TypeDescriptor.FromSymbol(attribute.GetNamedArgumentValue<ITypeSymbol?>("Converter")),
+            attribute
+                .GetNamedArgumentValues<ITypeSymbol>("Validators")
+                .Select(TypeDescriptor.FromSymbol)
+                .ToArray()
+        );
+}

CliFx.SourceGeneration/SemanticModel/CommandParameterSymbol.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using CliFx.SourceGeneration.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration.SemanticModel;
+
+internal partial class CommandParameterSymbol(
+    PropertyDescriptor property,
+    bool isSequence,
+    int order,
+    string name,
+    bool isRequired,
+    string? description,
+    TypeDescriptor? converterType,
+    IReadOnlyList<TypeDescriptor> validatorTypes
+) : CommandInputSymbol(property, isSequence, description, converterType, validatorTypes)
+{
+    public int Order { get; } = order;
+
+    public string Name { get; } = name;
+
+    public bool IsRequired { get; } = isRequired;
+}
+
+internal partial class CommandParameterSymbol : IEquatable<CommandParameterSymbol>
+{
+    public bool Equals(CommandParameterSymbol? other)
+    {
+        if (ReferenceEquals(null, other))
+            return false;
+        if (ReferenceEquals(this, other))
+            return true;
+
+        return base.Equals(other)
+            && Order == other.Order
+            && Name == other.Name
+            && IsRequired == other.IsRequired;
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (ReferenceEquals(null, obj))
+            return false;
+        if (ReferenceEquals(this, obj))
+            return true;
+        if (obj.GetType() != GetType())
+            return false;
+
+        return Equals((CommandParameterSymbol)obj);
+    }
+
+    public override int GetHashCode() =>
+        HashCode.Combine(base.GetHashCode(), Order, Name, IsRequired);
+}
+
+internal partial class CommandParameterSymbol
+{
+    public static CommandParameterSymbol FromSymbol(
+        IPropertySymbol property,
+        AttributeData attribute
+    ) =>
+        new(
+            PropertyDescriptor.FromSymbol(property),
+            IsSequenceType(property.Type),
+            (int)attribute.ConstructorArguments.First().Value!,
+            attribute.GetNamedArgumentValue("Name", default(string)),
+            attribute.GetNamedArgumentValue("IsRequired", true),
+            attribute.GetNamedArgumentValue("Description", default(string)),
+            TypeDescriptor.FromSymbol(attribute.GetNamedArgumentValue<ITypeSymbol>("Converter")),
+            attribute
+                .GetNamedArgumentValues<ITypeSymbol>("Validators")
+                .Select(TypeDescriptor.FromSymbol)
+                .ToArray()
+        );
+}

CliFx.SourceGeneration/SemanticModel/CommandSymbol.cs

@@ -0,0 +1,167 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using CliFx.SourceGeneration.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration.SemanticModel;
+
+internal partial class CommandSymbol(
+    TypeDescriptor type,
+    string? name,
+    string? description,
+    IReadOnlyList<CommandInputSymbol> inputs
+)
+{
+    public TypeDescriptor Type { get; } = type;
+
+    public string? Name { get; } = name;
+
+    public string? Description { get; } = description;
+
+    public IReadOnlyList<CommandInputSymbol> Inputs { get; } = inputs;
+
+    public IReadOnlyList<CommandParameterSymbol> Parameters =>
+        Inputs.OfType<CommandParameterSymbol>().ToArray();
+
+    public IReadOnlyList<CommandOptionSymbol> Options =>
+        Inputs.OfType<CommandOptionSymbol>().ToArray();
+
+    private string GeneratePropertyBindingInitializationCode(PropertyDescriptor property) =>
+        // lang=csharp
+        $$"""
+            new CliFx.Schema.PropertyBinding<{{Type.FullyQualifiedName}}, {{property
+                .Type
+                .FullyQualifiedName}}>(
+                (obj) => obj.{{property.Name}},
+                (obj, value) => obj.{{property.Name}} = value
+            )
+            """;
+
+    private string GenerateSchemaInitializationCode(CommandInputSymbol input) =>
+        input switch
+        {
+            CommandParameterSymbol parameter
+                =>
+                // lang=csharp
+                $$"""
+                    new CliFx.Schema.CommandParameterSchema<{{Type.FullyQualifiedName}}, {{parameter
+                        .Property
+                        .Type
+                        .FullyQualifiedName}}>(
+                        {{GeneratePropertyBindingInitializationCode(parameter.Property)}},
+                        {{parameter.IsSequence}},
+                        {{parameter.Order}},
+                        "{{parameter.Name}}",
+                        {{parameter.IsRequired}},
+                        "{{parameter.Description}}",
+                        // TODO,
+                        // TODO
+                    );
+                    """,
+            CommandOptionSymbol option
+                =>
+                // lang=csharp
+                $$"""
+                    new CliFx.Schema.CommandOptionSchema<{{Type.FullyQualifiedName}}, {{option
+                        .Property
+                        .Type
+                        .FullyQualifiedName}}>(
+                        {{GeneratePropertyBindingInitializationCode(option.Property)}},
+                        {{option.IsSequence}},
+                        "{{option.Name}}",
+                        '{{option.ShortName}}',
+                        "{{option.EnvironmentVariable}}",
+                        {{option.IsRequired}},
+                        "{{option.Description}}",
+                        // TODO,
+                        // TODO
+                    );
+                    """,
+            _ => throw new ArgumentOutOfRangeException(nameof(input), input, null)
+        };
+
+    public string GenerateSchemaInitializationCode() =>
+            // lang=csharp
+            $$"""
+            new CliFx.Schema.CommandSchema<{{Type.FullyQualifiedName}}>(
+                "{{Name}}",
+                "{{Description}}",
+                new CliFx.Schema.CommandInputSchema[]
+                {
+                    {{Inputs.Select(GenerateSchemaInitializationCode).JoinToString(",\n")}}
+                }
+            )
+            """;
+}
+
+internal partial class CommandSymbol : IEquatable<CommandSymbol>
+{
+    public bool Equals(CommandSymbol? other)
+    {
+        if (ReferenceEquals(null, other))
+            return false;
+        if (ReferenceEquals(this, other))
+            return true;
+
+        return Type.Equals(other.Type)
+            && Name == other.Name
+            && Description == other.Description
+            && Inputs.SequenceEqual(other.Inputs);
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (ReferenceEquals(null, obj))
+            return false;
+        if (ReferenceEquals(this, obj))
+            return true;
+        if (obj.GetType() != GetType())
+            return false;
+
+        return Equals((CommandSymbol)obj);
+    }
+
+    public override int GetHashCode() => HashCode.Combine(Type, Name, Description, Inputs);
+}
+
+internal partial class CommandSymbol
+{
+    public static CommandSymbol FromSymbol(INamedTypeSymbol symbol, AttributeData attribute)
+    {
+        var inputs = new List<CommandInputSymbol>();
+        foreach (var property in symbol.GetMembers().OfType<IPropertySymbol>())
+        {
+            var parameterAttribute = property
+                .GetAttributes()
+                .FirstOrDefault(a =>
+                    a.AttributeClass?.Name == KnownSymbolNames.CliFxCommandParameterAttribute
+                );
+
+            if (parameterAttribute is not null)
+            {
+                inputs.Add(CommandParameterSymbol.FromSymbol(property, parameterAttribute));
+                continue;
+            }
+
+            var optionAttribute = property
+                .GetAttributes()
+                .FirstOrDefault(a =>
+                    a.AttributeClass?.Name == KnownSymbolNames.CliFxCommandOptionAttribute
+                );
+
+            if (optionAttribute is not null)
+            {
+                inputs.Add(CommandOptionSymbol.FromSymbol(property, optionAttribute));
+                continue;
+            }
+        }
+
+        return new CommandSymbol(
+            TypeDescriptor.FromSymbol(symbol),
+            attribute.ConstructorArguments.FirstOrDefault().Value as string,
+            attribute.GetNamedArgumentValue("Description", default(string)),
+            inputs
+        );
+    }
+}

CliFx.SourceGeneration/SemanticModel/KnownSymbolNames.cs

@@ -0,0 +1,10 @@
+namespace CliFx.SourceGeneration.SemanticModel;
+
+internal static class KnownSymbolNames
+{
+    public const string CliFxCommandInterface = "CliFx.ICommand";
+    public const string CliFxCommandAttribute = "CliFx.Attributes.CommandAttribute";
+    public const string CliFxCommandParameterAttribute =
+        "CliFx.Attributes.CommandParameterAttribute";
+    public const string CliFxCommandOptionAttribute = "CliFx.Attributes.CommandOptionAttribute";
+}

CliFx.SourceGeneration/SemanticModel/PropertyDescriptor.cs

@@ -0,0 +1,44 @@
+using System;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration.SemanticModel;
+
+internal partial class PropertyDescriptor(TypeDescriptor type, string name)
+{
+    public TypeDescriptor Type { get; } = type;
+
+    public string Name { get; } = name;
+}
+
+internal partial class PropertyDescriptor : IEquatable<PropertyDescriptor>
+{
+    public bool Equals(PropertyDescriptor? other)
+    {
+        if (ReferenceEquals(null, other))
+            return false;
+        if (ReferenceEquals(this, other))
+            return true;
+
+        return Type.Equals(other.Type) && Name == other.Name;
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (ReferenceEquals(null, obj))
+            return false;
+        if (ReferenceEquals(this, obj))
+            return true;
+        if (obj.GetType() != GetType())
+            return false;
+
+        return Equals((PropertyDescriptor)obj);
+    }
+
+    public override int GetHashCode() => HashCode.Combine(Type, Name);
+}
+
+internal partial class PropertyDescriptor
+{
+    public static PropertyDescriptor FromSymbol(IPropertySymbol symbol) =>
+        new(TypeDescriptor.FromSymbol(symbol.Type), symbol.Name);
+}

CliFx.SourceGeneration/SemanticModel/TypeDescriptor.cs

@@ -0,0 +1,47 @@
+using System;
+using CliFx.SourceGeneration.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration.SemanticModel;
+
+internal partial class TypeDescriptor(string fullyQualifiedName)
+{
+    public string FullyQualifiedName { get; } = fullyQualifiedName;
+
+    public string Namespace { get; } = fullyQualifiedName.SubstringUntilLast(".");
+
+    public string Name { get; } = fullyQualifiedName.SubstringAfterLast(".");
+}
+
+internal partial class TypeDescriptor : IEquatable<TypeDescriptor>
+{
+    public bool Equals(TypeDescriptor? other)
+    {
+        if (ReferenceEquals(null, other))
+            return false;
+        if (ReferenceEquals(this, other))
+            return true;
+
+        return FullyQualifiedName == other.FullyQualifiedName;
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (ReferenceEquals(null, obj))
+            return false;
+        if (ReferenceEquals(this, obj))
+            return true;
+        if (obj.GetType() != GetType())
+            return false;
+
+        return Equals((TypeDescriptor)obj);
+    }
+
+    public override int GetHashCode() => FullyQualifiedName.GetHashCode();
+}
+
+internal partial class TypeDescriptor
+{
+    public static TypeDescriptor FromSymbol(ITypeSymbol symbol) =>
+        new(symbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat));
+}

CliFx.SourceGeneration/Utils/Extensions/CollectionExtensions.cs

@@ -0,0 +1,16 @@
+using System.Collections.Generic;
+
+namespace CliFx.SourceGeneration.Utils.Extensions;
+
+internal static class CollectionExtensions
+{
+    public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T?> source)
+        where T : class
+    {
+        foreach (var i in source)
+        {
+            if (i is not null)
+                yield return i;
+        }
+    }
+}

CliFx.SourceGeneration/Utils/Extensions/GenericExtensions.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace CliFx.SourceGeneration.Utils.Extensions;
+
+internal static class GenericExtensions
+{
+    public static TOut Pipe<TIn, TOut>(this TIn input, Func<TIn, TOut> transform) =>
+        transform(input);
+}

CliFx.SourceGeneration/Utils/Extensions/RoslynExtensions.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using Microsoft.CodeAnalysis;
+
+namespace CliFx.SourceGeneration.Utils.Extensions;
+
+internal static class RoslynExtensions
+{
+    public static bool DisplayNameMatches(this ISymbol symbol, string name) =>
+        string.Equals(
+            // Fully qualified name, without `global::`
+            symbol.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat),
+            name,
+            StringComparison.Ordinal
+        );
+
+    public static T GetNamedArgumentValue<T>(
+        this AttributeData attribute,
+        string name,
+        T defaultValue = default
+    ) =>
+        attribute.NamedArguments.FirstOrDefault(i => i.Key == name).Value.Value is T valueAsT
+            ? valueAsT
+            : defaultValue;
+
+    public static IReadOnlyList<T> GetNamedArgumentValues<T>(
+        this AttributeData attribute,
+        string name
+    )
+        where T : class =>
+        attribute.NamedArguments.FirstOrDefault(i => i.Key == name).Value.Values.CastArray<T>();
+
+    public static IncrementalValuesProvider<T> WhereNotNull<T>(
+        this IncrementalValuesProvider<T?> values
+    )
+        where T : class => values.Where(i => i is not null);
+}

CliFx.SourceGeneration/Utils/Extensions/StringExtensions.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+
+namespace CliFx.SourceGeneration.Utils.Extensions;
+
+internal static class StringExtensions
+{
+    public static string SubstringUntilLast(
+        this string str,
+        string sub,
+        StringComparison comparison = StringComparison.Ordinal
+    )
+    {
+        var index = str.LastIndexOf(sub, comparison);
+        return index < 0 ? str : str[..index];
+    }
+
+    public static string SubstringAfterLast(
+        this string str,
+        string sub,
+        StringComparison comparison = StringComparison.Ordinal
+    )
+    {
+        var index = str.LastIndexOf(sub, comparison);
+        return index >= 0 ? str.Substring(index + sub.Length, str.Length - index - sub.Length) : "";
+    }
+
+    public static string JoinToString<T>(this IEnumerable<T> source, string separator) =>
+        string.Join(separator, source);
+}

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

@@ -1,13 +1,18 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
+    <ApplicationIcon>../favicon.ico</ApplicationIcon>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="CSharpier.MsBuild" Version="0.30.6" PrivateAssets="all" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\CliFx\CliFx.csproj" />
+    <ProjectReference Include="..\CliFx.SourceGeneration\CliFx.SourceGeneration.csproj" ReferenceOutputAssembly="false" OutputItemType="analyzer" />
   </ItemGroup>
 
 </Project>

CliFx.Tests.Dummy/Commands/CancellationTestCommand.cs

@@ -0,0 +1,27 @@
+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.WriteLine("Started.");
+
+            await Task.Delay(TimeSpan.FromSeconds(3), console.RegisterCancellationHandler());
+
+            console.WriteLine("Completed.");
+        }
+        catch (OperationCanceledException)
+        {
+            console.WriteLine("Cancelled.");
+            throw;
+        }
+    }
+}

CliFx.Tests.Dummy/Commands/ConsoleTestCommand.cs

@@ -1,23 +1,23 @@
 using System;
 using System.Threading.Tasks;
 using CliFx.Attributes;
+using CliFx.Infrastructure;
 
-namespace CliFx.Tests.Dummy.Commands
+namespace CliFx.Tests.Dummy.Commands;
+
+[Command("console-test")]
+public class ConsoleTestCommand : ICommand
 {
-    [Command("console-test")]
-    public class ConsoleTestCommand : ICommand
-    {
     public ValueTask ExecuteAsync(IConsole console)
     {
         var input = console.Input.ReadToEnd();
 
-            console.WithColors(ConsoleColor.Black, ConsoleColor.White, () =>
+        using (console.WithColors(ConsoleColor.Black, ConsoleColor.White))
         {
             console.Output.WriteLine(input);
             console.Error.WriteLine(input);
-            });
+        }
 
         return default;
     }
-    }
 }

CliFx.Tests.Dummy/Commands/EnvironmentTestCommand.cs

@@ -0,0 +1,18 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Infrastructure;
+
+namespace CliFx.Tests.Dummy.Commands;
+
+[Command("env-test")]
+public class EnvironmentTestCommand : ICommand
+{
+    [CommandOption("target", EnvironmentVariable = "ENV_TARGET")]
+    public string GreetingTarget { get; init; } = "World";
+
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        console.WriteLine($"Hello {GreetingTarget}!");
+        return default;
+    }
+}

CliFx.Tests.Dummy/Commands/HelloWorldCommand.cs

@@ -1,19 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests.Dummy.Commands
-{
-    [Command]
-    public class HelloWorldCommand : ICommand
-    {
-        [CommandOption("target", EnvironmentVariableName = "ENV_TARGET")]
-        public string Target { get; set; } = "World";
-
-        public ValueTask ExecuteAsync(IConsole console)
-        {
-            console.Output.WriteLine($"Hello {Target}!");
-
-            return default;
-        }
-    }
-}

CliFx.Tests.Dummy/Program.cs

@@ -1,21 +1,28 @@
-using System.Reflection;
+using System;
+using System.IO;
+using System.Reflection;
 using System.Threading.Tasks;
 
-namespace CliFx.Tests.Dummy
+namespace CliFx.Tests.Dummy;
+
+// This dummy application is used in tests for scenarios that require an external process to properly verify
+public static class Program
 {
-    public static partial class Program
+    // Path to the apphost
-    {
+    public static string FilePath { get; } =
-        public static Assembly Assembly { get; } = typeof(Program).Assembly;
+        Path.ChangeExtension(
+            Assembly.GetExecutingAssembly().Location,
+            OperatingSystem.IsWindows() ? "exe" : null
+        );
 
-        public static string Location { get; } = Assembly.Location;
+    public static async Task Main()
-    }
-
-    public static partial class Program
     {
-        public static async Task Main() =>
+        // Make sure color codes are not produced because we rely on the output in tests
-            await new CliApplicationBuilder()
+        Environment.SetEnvironmentVariable(
-                .AddCommandsFromThisAssembly()
+            "DOTNET_SYSTEM_CONSOLE_ALLOW_ANSI_COLOR_REDIRECTION",
-                .Build()
+            "false"
-                .RunAsync();
+        );
+
+        await new CliApplicationBuilder().AddCommandsFromThisAssembly().Build().RunAsync();
     }
 }

CliFx.Tests/ApplicationSpecs.Commands.cs

@@ -1,137 +0,0 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class ApplicationSpecs
-    {
-        [Command]
-        private class NonImplementedCommand
-        {
-        }
-
-        private class NonAnnotatedCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("dup")]
-        private class DuplicateNameCommandA : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("dup")]
-        private class DuplicateNameCommandB : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateParameterOrderCommand : ICommand
-        {
-            [CommandParameter(13)]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(13)]
-            public string? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateParameterNameCommand : ICommand
-        {
-            [CommandParameter(0, Name = "param")]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(1, Name = "param")]
-            public string? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class MultipleNonScalarParametersCommand : ICommand
-        {
-            [CommandParameter(0)]
-            public IReadOnlyList<string>? ParameterA { get; set; }
-
-            [CommandParameter(1)]
-            public IReadOnlyList<string>? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class NonLastNonScalarParameterCommand : ICommand
-        {
-            [CommandParameter(0)]
-            public IReadOnlyList<string>? ParameterA { get; set; }
-
-            [CommandParameter(1)]
-            public string? ParameterB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateOptionNamesCommand : ICommand
-        {
-            [CommandOption("fruits")]
-            public string? Apples { get; set; }
-
-            [CommandOption("fruits")]
-            public string? Oranges { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateOptionShortNamesCommand : ICommand
-        {
-            [CommandOption('x')]
-            public string? OptionA { get; set; }
-
-            [CommandOption('x')]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class DuplicateOptionEnvironmentVariableNamesCommand : ICommand
-        {
-            [CommandOption("option-a", EnvironmentVariableName = "ENV_VAR")]
-            public string? OptionA { get; set; }
-
-            [CommandOption("option-b", EnvironmentVariableName = "ENV_VAR")]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class ValidCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("hidden", Description = "Description")]
-        private class HiddenPropertiesCommand : ICommand
-        {
-            [CommandParameter(13, Name = "param", Description = "Param description")]
-            public string? Parameter { get; set; }
-
-            [CommandOption("option", 'o', Description = "Option description", EnvironmentVariableName = "ENV")]
-            public string? Option { get; set; }
-
-            public string? HiddenA { get; set; }
-
-            public bool? HiddenB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/ApplicationSpecs.cs

@@ -1,197 +1,71 @@
 using System;
-using System.IO;
+using System.Collections.Generic;
-using CliFx.Domain;
+using System.Threading.Tasks;
-using CliFx.Exceptions;
+using CliFx.Tests.Utils;
 using FluentAssertions;
 using Xunit;
+using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class ApplicationSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
 {
-    public partial class ApplicationSpecs
-    {
     [Fact]
-        public void Application_can_be_created_with_a_default_configuration()
+    public async Task I_can_create_an_application_with_the_default_configuration()
     {
         // Act
         var app = new CliApplicationBuilder()
             .AddCommandsFromThisAssembly()
+            .UseConsole(FakeConsole)
             .Build();
 
+        var exitCode = await app.RunAsync([], new Dictionary<string, string>());
+
         // Assert
-            app.Should().NotBeNull();
+        exitCode.Should().Be(0);
     }
 
     [Fact]
-        public void Application_can_be_created_with_a_custom_configuration()
+    public async Task I_can_create_an_application_with_a_custom_configuration()
     {
         // Act
         var app = new CliApplicationBuilder()
-                .AddCommand(typeof(ValidCommand))
+            .AddCommand<NoOpCommand>()
-                .AddCommandsFrom(typeof(ValidCommand).Assembly)
+            .AddCommandsFrom(typeof(NoOpCommand).Assembly)
-                .AddCommands(new[] {typeof(ValidCommand)})
+            .AddCommands([typeof(NoOpCommand)])
-                .AddCommandsFrom(new[] {typeof(ValidCommand).Assembly})
+            .AddCommandsFrom([typeof(NoOpCommand).Assembly])
             .AddCommandsFromThisAssembly()
             .AllowDebugMode()
             .AllowPreviewMode()
-                .UseTitle("test")
+            .SetTitle("test")
-                .UseExecutableName("test")
+            .SetExecutableName("test")
-                .UseVersionText("test")
+            .SetVersion("test")
-                .UseDescription("test")
+            .SetDescription("test")
-                .UseConsole(new VirtualConsole(Stream.Null))
+            .UseConsole(FakeConsole)
-                .UseTypeActivator(Activator.CreateInstance)
+            .UseTypeActivator(Activator.CreateInstance!)
             .Build();
 
+        var exitCode = await app.RunAsync([], new Dictionary<string, string>());
+
         // Assert
-            app.Should().NotBeNull();
+        exitCode.Should().Be(0);
     }
 
     [Fact]
-        public void At_least_one_command_must_be_defined_in_an_application()
+    public async Task I_can_try_to_create_an_application_and_get_an_error_if_it_has_invalid_commands()
     {
-            // Arrange
-            var commandTypes = Array.Empty<Type>();
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Commands_must_implement_the_corresponding_interface()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(NonImplementedCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Commands_must_be_annotated_by_an_attribute()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(NonAnnotatedCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Commands_must_have_unique_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateNameCommandA), typeof(DuplicateNameCommandB)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_parameters_must_have_unique_order()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateParameterOrderCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_parameters_must_have_unique_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateParameterNameCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_parameter_can_be_non_scalar_only_if_no_other_such_parameter_is_present()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(MultipleNonScalarParametersCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_parameter_can_be_non_scalar_only_if_it_is_the_last_in_order()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(NonLastNonScalarParameterCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_options_must_have_unique_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateOptionNamesCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_options_must_have_unique_short_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateOptionShortNamesCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_options_must_have_unique_environment_variable_names()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(DuplicateOptionEnvironmentVariableNamesCommand)};
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() => ApplicationSchema.Resolve(commandTypes));
-        }
-
-        [Fact]
-        public void Command_options_and_parameters_must_be_annotated_by_corresponding_attributes()
-        {
-            // Arrange
-            var commandTypes = new[] {typeof(HiddenPropertiesCommand)};
-
         // Act
-            var schema = ApplicationSchema.Resolve(commandTypes);
+        var app = new CliApplicationBuilder()
+            .AddCommand(typeof(ApplicationSpecs))
+            .UseConsole(FakeConsole)
+            .Build();
+
+        var exitCode = await app.RunAsync([], new Dictionary<string, string>());
 
         // Assert
-            schema.Should().BeEquivalentTo(new ApplicationSchema(new[]
+        exitCode.Should().NotBe(0);
-            {
-                new CommandSchema(
-                    typeof(HiddenPropertiesCommand),
-                    "hidden",
-                    "Description",
-                    new[]
-                    {
-                        new CommandParameterSchema(
-                            typeof(HiddenPropertiesCommand).GetProperty(nameof(HiddenPropertiesCommand.Parameter)),
-                            13,
-                            "param",
-                            "Param description")
-                    },
-                    new[]
-                    {
-                        new CommandOptionSchema(
-                            typeof(HiddenPropertiesCommand).GetProperty(nameof(HiddenPropertiesCommand.Option)),
-                            "option",
-                            'o',
-                            "ENV",
-                            false,
-                            "Option description")
-                    })
-            }));
 
-            schema.ToString().Should().NotBeNullOrWhiteSpace(); // this is only for coverage, I'm sorry
+        var stdErr = FakeConsole.ReadErrorString();
-        }
+        stdErr.Should().Contain("not a valid command");
     }
 }

CliFx.Tests/ArgumentBindingSpecs.Commands.cs

@@ -1,191 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class ArgumentBindingSpecs
-    {
-        [Command]
-        private class AllSupportedTypesCommand : ICommand
-        {
-            [CommandOption(nameof(Object))]
-            public object? Object { get; set; } = 42;
-
-            [CommandOption(nameof(String))]
-            public string? String { get; set; } = "foo bar";
-
-            [CommandOption(nameof(Bool))]
-            public bool Bool { get; set; }
-
-            [CommandOption(nameof(Char))]
-            public char Char { get; set; }
-
-            [CommandOption(nameof(Sbyte))]
-            public sbyte Sbyte { get; set; }
-
-            [CommandOption(nameof(Byte))]
-            public byte Byte { get; set; }
-
-            [CommandOption(nameof(Short))]
-            public short Short { get; set; }
-
-            [CommandOption(nameof(Ushort))]
-            public ushort Ushort { get; set; }
-
-            [CommandOption(nameof(Int))]
-            public int Int { get; set; }
-
-            [CommandOption(nameof(Uint))]
-            public uint Uint { get; set; }
-
-            [CommandOption(nameof(Long))]
-            public long Long { get; set; }
-
-            [CommandOption(nameof(Ulong))]
-            public ulong Ulong { get; set; }
-
-            [CommandOption(nameof(Float))]
-            public float Float { get; set; }
-
-            [CommandOption(nameof(Double))]
-            public double Double { get; set; }
-
-            [CommandOption(nameof(Decimal))]
-            public decimal Decimal { get; set; }
-
-            [CommandOption(nameof(DateTime))]
-            public DateTime DateTime { get; set; }
-
-            [CommandOption(nameof(DateTimeOffset))]
-            public DateTimeOffset DateTimeOffset { get; set; }
-
-            [CommandOption(nameof(TimeSpan))]
-            public TimeSpan TimeSpan { get; set; }
-
-            [CommandOption(nameof(CustomEnum))]
-            public CustomEnum CustomEnum { get; set; }
-
-            [CommandOption(nameof(IntNullable))]
-            public int? IntNullable { get; set; }
-
-            [CommandOption(nameof(CustomEnumNullable))]
-            public CustomEnum? CustomEnumNullable { get; set; }
-
-            [CommandOption(nameof(TimeSpanNullable))]
-            public TimeSpan? TimeSpanNullable { get; set; }
-
-            [CommandOption(nameof(TestStringConstructable))]
-            public StringConstructable? TestStringConstructable { get; set; }
-
-            [CommandOption(nameof(TestStringParseable))]
-            public StringParseable? TestStringParseable { get; set; }
-
-            [CommandOption(nameof(TestStringParseableWithFormatProvider))]
-            public StringParseableWithFormatProvider? TestStringParseableWithFormatProvider { get; set; }
-
-            [CommandOption(nameof(ObjectArray))]
-            public object[]? ObjectArray { get; set; }
-
-            [CommandOption(nameof(StringArray))]
-            public string[]? StringArray { get; set; }
-
-            [CommandOption(nameof(IntArray))]
-            public int[]? IntArray { get; set; }
-
-            [CommandOption(nameof(CustomEnumArray))]
-            public CustomEnum[]? CustomEnumArray { get; set; }
-
-            [CommandOption(nameof(IntNullableArray))]
-            public int?[]? IntNullableArray { get; set; }
-
-            [CommandOption(nameof(TestStringConstructableArray))]
-            public StringConstructable[]? TestStringConstructableArray { get; set; }
-
-            [CommandOption(nameof(Enumerable))]
-            public IEnumerable? Enumerable { get; set; }
-
-            [CommandOption(nameof(StringEnumerable))]
-            public IEnumerable<string>? StringEnumerable { get; set; }
-
-            [CommandOption(nameof(StringReadOnlyList))]
-            public IReadOnlyList<string>? StringReadOnlyList { get; set; }
-
-            [CommandOption(nameof(StringList))]
-            public List<string>? StringList { get; set; }
-
-            [CommandOption(nameof(StringHashSet))]
-            public HashSet<string>? StringHashSet { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class ArrayOptionCommand : ICommand
-        {
-            [CommandOption("option", 'o')]
-            public IReadOnlyList<string>? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class RequiredOptionCommand : ICommand
-        {
-            [CommandOption(nameof(OptionA))]
-            public string? OptionA { get; set; }
-
-            [CommandOption(nameof(OptionB), IsRequired = true)]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class ParametersCommand : ICommand
-        {
-            [CommandParameter(0)]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(1)]
-            public string? ParameterB { get; set; }
-
-            [CommandParameter(2)]
-            public IReadOnlyList<string>? ParameterC { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class UnsupportedPropertyTypeCommand : ICommand
-        {
-            [CommandOption(nameof(Option))]
-            public DummyType? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class UnsupportedEnumerablePropertyTypeCommand : ICommand
-        {
-            [CommandOption(nameof(Option))]
-            public CustomEnumerable<string>? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class NoParameterCommand : ICommand
-        {
-            [CommandOption(nameof(OptionA))]
-            public string? OptionA { get; set; }
-
-            [CommandOption(nameof(OptionB))]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/ArgumentBindingSpecs.Types.cs

@@ -1,64 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-
-namespace CliFx.Tests
-{
-    public partial class ArgumentBindingSpecs
-    {
-        private enum CustomEnum
-        {
-            Value1 = 1,
-            Value2 = 2,
-            Value3 = 3
-        }
-
-        private class StringConstructable
-        {
-            public string Value { get; }
-
-            public StringConstructable(string value)
-            {
-                Value = value;
-            }
-        }
-
-        private class StringParseable
-        {
-            public string Value { get; }
-
-            private StringParseable(string value)
-            {
-                Value = value;
-            }
-
-            public static StringParseable Parse(string value) => new StringParseable(value);
-        }
-
-        private class StringParseableWithFormatProvider
-        {
-            public string Value { get; }
-
-            private StringParseableWithFormatProvider(string value)
-            {
-                Value = value;
-            }
-
-            public static StringParseableWithFormatProvider Parse(string value, IFormatProvider formatProvider) =>
-                new StringParseableWithFormatProvider(value + " " + formatProvider);
-        }
-
-        private class DummyType
-        {
-        }
-
-        public class CustomEnumerable<T> : IEnumerable<T>
-        {
-            private readonly T[] _arr = new T[0];
-
-            public IEnumerator<T> GetEnumerator() => ((IEnumerable<T>) _arr).GetEnumerator();
-
-            IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
-        }
-    }
-}

CliFx.Tests/ArgumentSyntaxSpecs.cs

@@ -1,315 +0,0 @@
-using System;
-using CliFx.Domain;
-using FluentAssertions;
-using Xunit;
-
-namespace CliFx.Tests
-{
-    public class ArgumentSyntaxSpecs
-    {
-        [Fact]
-        public void Input_is_empty_if_no_arguments_are_provided()
-        {
-            // Arrange
-            var args = Array.Empty<string>();
-
-            // Act
-            var input = CommandLineInput.Parse(args);
-
-            // Assert
-            input.Should().BeEquivalentTo(CommandLineInput.Empty);
-        }
-
-        public static object[][] DirectivesTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"[preview]"},
-                new CommandLineInputBuilder()
-                    .AddDirective("preview")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"[preview]", "[debug]"},
-                new CommandLineInputBuilder()
-                    .AddDirective("preview")
-                    .AddDirective("debug")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(DirectivesTestData))]
-        internal void Directive_can_be_enabled_by_specifying_its_name_in_square_brackets(string[] arguments, CommandLineInput expectedInput)
-        {
-            // Act
-            var input = CommandLineInput.Parse(arguments);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-
-        public static object[][] OptionsTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"--option"},
-                new CommandLineInputBuilder()
-                    .AddOption("option")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option", "value"},
-                new CommandLineInputBuilder()
-                    .AddOption("option", "value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option", "value1", "value2"},
-                new CommandLineInputBuilder()
-                    .AddOption("option", "value1", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option", "same value"},
-                new CommandLineInputBuilder()
-                    .AddOption("option", "same value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "--option2"},
-                new CommandLineInputBuilder()
-                    .AddOption("option1")
-                    .AddOption("option2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "value1", "--option2", "value2"},
-                new CommandLineInputBuilder()
-                    .AddOption("option1", "value1")
-                    .AddOption("option2", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "value1", "value2", "--option2", "value3", "value4"},
-                new CommandLineInputBuilder()
-                    .AddOption("option1", "value1", "value2")
-                    .AddOption("option2", "value3", "value4")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"--option1", "value1", "value2", "--option2"},
-                new CommandLineInputBuilder()
-                    .AddOption("option1", "value1", "value2")
-                    .AddOption("option2")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(OptionsTestData))]
-        internal void Option_can_be_set_by_specifying_its_name_after_two_dashes(string[] arguments, CommandLineInput expectedInput)
-        {
-            // Act
-            var input = CommandLineInput.Parse(arguments);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-
-        public static object[][] ShortOptionsTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"-o"},
-                new CommandLineInputBuilder()
-                    .AddOption("o")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-o", "value"},
-                new CommandLineInputBuilder()
-                    .AddOption("o", "value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-o", "value1", "value2"},
-                new CommandLineInputBuilder()
-                    .AddOption("o", "value1", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-o", "same value"},
-                new CommandLineInputBuilder()
-                    .AddOption("o", "same value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "-b"},
-                new CommandLineInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "value1", "-b", "value2"},
-                new CommandLineInputBuilder()
-                    .AddOption("a", "value1")
-                    .AddOption("b", "value2")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "value1", "value2", "-b", "value3", "value4"},
-                new CommandLineInputBuilder()
-                    .AddOption("a", "value1", "value2")
-                    .AddOption("b", "value3", "value4")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-a", "value1", "value2", "-b"},
-                new CommandLineInputBuilder()
-                    .AddOption("a", "value1", "value2")
-                    .AddOption("b")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-abc"},
-                new CommandLineInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-abc", "value"},
-                new CommandLineInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c", "value")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"-abc", "value1", "value2"},
-                new CommandLineInputBuilder()
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c", "value1", "value2")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(ShortOptionsTestData))]
-        internal void Option_can_be_set_by_specifying_its_short_name_after_a_single_dash(string[] arguments, CommandLineInput expectedInput)
-        {
-            // Act
-            var input = CommandLineInput.Parse(arguments);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-
-        public static object[][] UnboundArgumentsTestData => new[]
-        {
-            new object[]
-            {
-                new[] {"foo"},
-                new CommandLineInputBuilder()
-                    .AddUnboundArgument("foo")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"foo", "bar"},
-                new CommandLineInputBuilder()
-                    .AddUnboundArgument("foo")
-                    .AddUnboundArgument("bar")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"[preview]", "foo"},
-                new CommandLineInputBuilder()
-                    .AddDirective("preview")
-                    .AddUnboundArgument("foo")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"foo", "--option", "value", "-abc"},
-                new CommandLineInputBuilder()
-                    .AddUnboundArgument("foo")
-                    .AddOption("option", "value")
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c")
-                    .Build()
-            },
-
-            new object[]
-            {
-                new[] {"[preview]", "[debug]", "foo", "bar", "--option", "value", "-abc"},
-                new CommandLineInputBuilder()
-                    .AddDirective("preview")
-                    .AddDirective("debug")
-                    .AddUnboundArgument("foo")
-                    .AddUnboundArgument("bar")
-                    .AddOption("option", "value")
-                    .AddOption("a")
-                    .AddOption("b")
-                    .AddOption("c")
-                    .Build()
-            }
-        };
-
-        [Theory]
-        [MemberData(nameof(UnboundArgumentsTestData))]
-        internal void Any_remaining_arguments_are_treated_as_unbound_arguments(string[] arguments, CommandLineInput expectedInput)
-        {
-            // Act
-            var input = CommandLineInput.Parse(arguments);
-
-            // Assert
-            input.Should().BeEquivalentTo(expectedInput);
-        }
-    }
-}

CliFx.Tests/CancellationSpecs.Commands.cs

@@ -1,27 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class CancellationSpecs
-    {
-        [Command("cancel")]
-        private class CancellableCommand : ICommand
-        {
-            public async ValueTask ExecuteAsync(IConsole console)
-            {
-                try
-                {
-                    await Task.Delay(TimeSpan.FromSeconds(3), console.GetCancellationToken());
-                    console.Output.WriteLine("Never printed");
-                }
-                catch (OperationCanceledException)
-                {
-                    console.Output.WriteLine("Cancellation requested");
-                    throw;
-                }
-            }
-        }
-    }
-}

CliFx.Tests/CancellationSpecs.cs

@@ -1,41 +1,107 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
+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;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class CancellationSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
 {
-    public partial class CancellationSpecs
+    [Fact(Timeout = 15000)]
-    {
+    public async Task I_can_configure_the_command_to_listen_to_the_interrupt_signal()
-        [Fact]
-        public async Task Command_can_perform_additional_cleanup_if_cancellation_is_requested()
     {
         // Arrange
         using var cts = new CancellationTokenSource();
 
-            await using var stdOut = new MemoryStream();
+        // We need to send the cancellation request right after the process has registered
-            var console = new VirtualConsole(output: stdOut, cancellationToken: cts.Token);
+        // 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(Dummy.Program.FilePath).WithArguments("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 I_can_configure_the_command_to_listen_to_the_interrupt_signal_when_running_in_isolation()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public async ValueTask ExecuteAsync(IConsole console)
+                {
+                    try
+                    {
+                        console.WriteLine("Started.");
+
+                        await Task.Delay(
+                            TimeSpan.FromSeconds(3),
+                            console.RegisterCancellationHandler()
+                        );
+
+                        console.WriteLine("Completed.");
+                    }
+                    catch (OperationCanceledException)
+                    {
+                        console.WriteLine("Cancelled.");
+                        throw;
+                    }
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
-                .AddCommand(typeof(CancellableCommand))
+            .AddCommand(commandType)
-                .UseConsole(console)
+            .UseConsole(FakeConsole)
             .Build();
 
+        FakeConsole.RequestCancellation(TimeSpan.FromSeconds(0.2));
+
         // Act
-            cts.CancelAfter(TimeSpan.FromSeconds(0.2));
-
         var exitCode = await application.RunAsync(
-                new[] {"cancel"},
+            [],
-                new Dictionary<string, string>());
+            new Dictionary<string, string>()
-
+        );
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
         // Assert
         exitCode.Should().NotBe(0);
-            stdOutData.Should().Be("Cancellation requested");
+
-        }
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().ConsistOfLines("Started.", "Cancelled.");
     }
 }

CliFx.Tests/CliFx.Tests.csproj

@@ -1,13 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <Import Project="../CliFx.props" />
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
-    <IsPackable>false</IsPackable>
-    <IsTestProject>true</IsTestProject>
-    <CollectCoverage>true</CollectCoverage>
-    <CoverletOutputFormat>opencover</CoverletOutputFormat>
-    <CoverletOutput>bin/$(Configuration)/Coverage.xml</CoverletOutput>
   </PropertyGroup>
 
   <ItemGroup>
@@ -15,12 +9,18 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="CliWrap" Version="3.0.0" />
+    <PackageReference Include="Basic.Reference.Assemblies.Net80" Version="1.8.0" />
-    <PackageReference Include="FluentAssertions" Version="5.10.2" />
+    <PackageReference Include="CliWrap" Version="3.7.1" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.5.0" />
+    <PackageReference Include="coverlet.collector" Version="6.0.4" PrivateAssets="all" />
-    <PackageReference Include="coverlet.msbuild" Version="2.8.0" PrivateAssets="all" />
+    <PackageReference Include="CSharpier.MsBuild" Version="0.30.6" PrivateAssets="all" />
-    <PackageReference Include="xunit" Version="2.4.1" />
+    <PackageReference Include="FluentAssertions" Version="8.0.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1" />
+    <PackageReference Include="GitHubActionsTestLogger" Version="2.4.1" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.11.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="9.0.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="PolyShim" Version="1.14.0" PrivateAssets="all" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.0.1" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>
@@ -28,12 +28,4 @@
     <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

@@ -1,72 +1,204 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
+using System.Text;
 using System.Threading.Tasks;
+using CliFx.Infrastructure;
+using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
 using CliWrap;
 using CliWrap.Buffered;
 using FluentAssertions;
 using Xunit;
+using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class ConsoleSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
 {
-    public class ConsoleSpecs
+    [Fact(Timeout = 15000)]
-    {
+    public async Task I_can_run_the_application_with_the_default_console_implementation_to_interact_with_the_system_console()
-        [Fact]
-        public async Task Real_implementation_of_console_maps_directly_to_system_console()
     {
+        // Can't verify our own console output, so using an external process for this test
+
         // Arrange
-            var command = "Hello world" | Cli.Wrap("dotnet")
+        var command =
-                .WithArguments(a => a
+            "Hello world" | Cli.Wrap(Dummy.Program.FilePath).WithArguments("console-test");
-                    .Add(Dummy.Program.Location)
-                    .Add("console-test"));
 
         // Act
         var result = await command.ExecuteBufferedAsync();
 
         // Assert
-            result.StandardOutput.TrimEnd().Should().Be("Hello world");
+        result.StandardOutput.Trim().Should().Be("Hello world");
-            result.StandardError.TrimEnd().Should().Be("Hello world");
+        result.StandardError.Trim().Should().Be("Hello world");
     }
 
     [Fact]
-        public void Fake_implementation_of_console_can_be_used_to_execute_commands_in_isolation()
+    public void I_can_run_the_application_on_a_system_with_a_custom_console_encoding_and_not_get_corrupted_output()
     {
         // Arrange
-            using var stdIn = new MemoryStream(Console.InputEncoding.GetBytes("input"));
+        using var buffer = new MemoryStream();
-            using var stdOut = new MemoryStream();
+        using var consoleWriter = new ConsoleWriter(FakeConsole, buffer, Encoding.UTF8);
-            using var stdErr = new MemoryStream();
-
-            var console = new VirtualConsole(
-                input: stdIn,
-                output: stdOut,
-                error: stdErr);
 
         // Act
-            console.Output.Write("output");
+        consoleWriter.Write("Hello world");
-            console.Error.Write("error");
+        consoleWriter.Flush();
 
-            var stdInData = console.Input.ReadToEnd();
+        // Assert
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray());
+        var outputBytes = buffer.ToArray();
-            var stdErrData = console.Error.Encoding.GetString(stdErr.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(
+            // lang=csharp
+            """
+            [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!");
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
 
         // Assert
-            stdInData.Should().Be("input");
+        exitCode.Should().Be(0);
-            stdOutData.Should().Be("output");
-            stdErrData.Should().Be("error");
 
-            console.Input.Should().NotBeSameAs(Console.In);
+        Console.OpenStandardInput().Should().NotBeSameAs(FakeConsole.Input.BaseStream);
-            console.Output.Should().NotBeSameAs(Console.Out);
+        Console.OpenStandardOutput().Should().NotBeSameAs(FakeConsole.Output.BaseStream);
-            console.Error.Should().NotBeSameAs(Console.Error);
+        Console.OpenStandardError().Should().NotBeSameAs(FakeConsole.Error.BaseStream);
 
-            console.IsInputRedirected.Should().BeTrue();
+        Console.ForegroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
-            console.IsOutputRedirected.Should().BeTrue();
+        Console.BackgroundColor.Should().NotBe(ConsoleColor.DarkMagenta);
-            console.IsErrorRedirected.Should().BeTrue();
 
-            console.ForegroundColor.Should().NotBe(Console.ForegroundColor);
+        // This fails because tests don't spawn a console window
-            console.BackgroundColor.Should().NotBe(Console.BackgroundColor);
+        //Console.WindowWidth.Should().Be(100);
+        //Console.WindowHeight.Should().Be(25);
+        //Console.CursorLeft.Should().NotBe(42);
+        //Console.CursorTop.Should().NotBe(24);
+
+        FakeConsole.IsInputRedirected.Should().BeTrue();
+        FakeConsole.IsOutputRedirected.Should().BeTrue();
+        FakeConsole.IsErrorRedirected.Should().BeTrue();
     }
+
+    [Fact]
+    public async Task I_can_run_the_application_with_the_fake_console_implementation_and_simulate_stream_interactions()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [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;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        FakeConsole.WriteInput("Hello world");
+
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // 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 I_can_run_the_application_with_the_fake_console_implementation_and_simulate_key_presses()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(console.ReadKey().Key);
+                    console.WriteLine(console.ReadKey().Key);
+                    console.WriteLine(console.ReadKey().Key);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        FakeConsole.EnqueueKey(new ConsoleKeyInfo('0', ConsoleKey.D0, false, false, false));
+        FakeConsole.EnqueueKey(new ConsoleKeyInfo('a', ConsoleKey.A, false, false, false));
+        FakeConsole.EnqueueKey(new ConsoleKeyInfo('\0', ConsoleKey.Backspace, false, false, false));
+
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().ConsistOfLines("D0", "A", "Backspace");
     }
 }

CliFx.Tests/ConversionSpecs.cs

@@ -0,0 +1,941 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
+using FluentAssertions;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace CliFx.Tests;
+
+public class ConversionSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
+{
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_string_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "xyz"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("xyz");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_an_object_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public object? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "xyz"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("xyz");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_boolean_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public bool Foo { get; init; }
+
+                [CommandOption('b')]
+                public bool Bar { get; init; }
+
+                [CommandOption('c')]
+                public bool Baz { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+                    console.WriteLine("Baz = " + Baz);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "true", "-b", "false", "-c"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = True", "Bar = False", "Baz = True");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_an_integer_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public int Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "32"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("32");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_double_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public double Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo.ToString(CultureInfo.InvariantCulture));
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "32.14"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("32.14");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_DateTimeOffset_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public DateTimeOffset Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo.ToString("u", CultureInfo.InvariantCulture));
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "1995-04-28Z"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("1995-04-28 00:00:00Z");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_TimeSpan_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public TimeSpan Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo.ToString(null, CultureInfo.InvariantCulture));
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "12:34:56"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("12:34:56");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_an_enum_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public enum CustomEnum { One = 1, Two = 2, Three = 3 }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public CustomEnum Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine((int) Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "two"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("2");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_nullable_integer_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public int? Foo { get; init; }
+
+                [CommandOption('b')]
+                public int? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-b", "123"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = ", "Bar = 123");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_nullable_enum_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public enum CustomEnum { One = 1, Two = 2, Three = 3 }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public CustomEnum? Foo { get; init; }
+
+                [CommandOption('b')]
+                public CustomEnum? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + (int?) Foo);
+                    console.WriteLine("Bar = " + (int?) Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-b", "two"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = ", "Bar = 2");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_string_constructable_object_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public class CustomType
+            {
+                public string Value { get; }
+
+                public CustomType(string value) => Value = value;
+            }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public CustomType? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo.Value);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "xyz"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("xyz");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_string_parsable_object_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public class CustomTypeA
+            {
+                public string Value { get; }
+
+                private CustomTypeA(string value) => Value = value;
+
+                public static CustomTypeA Parse(string value) =>
+                    new CustomTypeA(value);
+            }
+
+            public class CustomTypeB
+            {
+                public string Value { get; }
+
+                private CustomTypeB(string value) => Value = value;
+
+                public static CustomTypeB Parse(string value, IFormatProvider formatProvider) =>
+                    new CustomTypeB(value);
+            }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public CustomTypeA? Foo { get; init; }
+
+                [CommandOption('b')]
+                public CustomTypeB? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo.Value);
+                    console.WriteLine("Bar = " + Bar.Value);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "hello", "-b", "world"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = hello", "Bar = world");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_property_with_a_custom_converter()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public class CustomConverter : BindingConverter<int>
+            {
+                public override int Convert(string rawValue) =>
+                    rawValue.Length;
+            }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f', Converter = typeof(CustomConverter))]
+                public int Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "hello world"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("11");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_string_array_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public string[]? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "one", "two", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_read_only_list_of_strings_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "one", "two", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_a_string_list_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public List<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "one", "two", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_a_parameter_or_an_option_to_an_integer_array_property()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public int[]? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "1", "13", "27"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("1", "13", "27");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_parameter_or_an_option_to_a_property_and_get_an_error_if_it_is_of_an_unsupported_type()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public class CustomType
+            {
+            }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public CustomType? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "xyz"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("has an unsupported underlying property type");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_parameter_or_an_option_to_a_non_scalar_property_and_get_an_error_if_it_is_of_an_unsupported_type()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public class CustomType : IEnumerable<object>
+            {
+                public IEnumerator<object> GetEnumerator() => Enumerable.Empty<object>().GetEnumerator();
+
+                IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+            }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public CustomType? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "one", "two"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("has an unsupported underlying property type");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_parameter_or_an_option_to_a_property_and_get_an_error_if_the_user_provides_an_invalid_value()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public int Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "12.34"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().NotBeNullOrWhiteSpace();
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_parameter_or_an_option_to_a_property_and_get_an_error_if_a_custom_validator_fails()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public class ValidatorA : BindingValidator<int>
+            {
+                public override BindingValidationError Validate(int value) => Ok();
+            }
+
+            public class ValidatorB : BindingValidator<int>
+            {
+                public override BindingValidationError Validate(int value) => Error("Hello world");
+            }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f', Validators = [typeof(ValidatorA), typeof(ValidatorB)])]
+                public int Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "12"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Hello world");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_parameter_or_an_option_to_a_string_parsable_property_and_get_an_error_if_the_parsing_fails()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public class CustomType
+            {
+                public string Value { get; }
+
+                private CustomType(string value) => Value = value;
+
+                public static CustomType Parse(string value) => throw new Exception("Hello world");
+            }
+
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public CustomType? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f", "bar"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Hello world");
+    }
+}

CliFx.Tests/DependencyInjectionSpecs.Commands.cs

@@ -1,37 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class DependencyInjectionSpecs
-    {
-        [Command]
-        private class WithoutDependenciesCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        private class DependencyA
-        {
-        }
-
-        private class DependencyB
-        {
-        }
-
-        [Command]
-        private class WithDependenciesCommand : ICommand
-        {
-            private readonly DependencyA _dependencyA;
-            private readonly DependencyB _dependencyB;
-
-            public WithDependenciesCommand(DependencyA dependencyA, DependencyB dependencyB)
-            {
-                _dependencyA = dependencyA;
-                _dependencyB = dependencyB;
-            }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/DependencyInjectionSpecs.cs

@@ -1,58 +0,0 @@
-using CliFx.Exceptions;
-using FluentAssertions;
-using Xunit;
-
-namespace CliFx.Tests
-{
-    public partial class DependencyInjectionSpecs
-    {
-        [Fact]
-        public void Default_type_activator_can_initialize_a_command_if_it_has_a_parameterless_constructor()
-        {
-            // Arrange
-            var activator = new DefaultTypeActivator();
-
-            // Act
-            var obj = activator.CreateInstance(typeof(WithoutDependenciesCommand));
-
-            // Assert
-            obj.Should().BeOfType<WithoutDependenciesCommand>();
-        }
-
-        [Fact]
-        public void Default_type_activator_cannot_initialize_a_command_if_it_does_not_have_a_parameterless_constructor()
-        {
-            // Arrange
-            var activator = new DefaultTypeActivator();
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() =>
-                activator.CreateInstance(typeof(WithDependenciesCommand)));
-        }
-
-        [Fact]
-        public void Delegate_type_activator_can_initialize_a_command_using_a_custom_function()
-        {
-            // Arrange
-            var activator = new DelegateTypeActivator(_ =>
-                new WithDependenciesCommand(new DependencyA(), new DependencyB()));
-
-            // Act
-            var obj = activator.CreateInstance(typeof(WithDependenciesCommand));
-
-            // Assert
-            obj.Should().BeOfType<WithDependenciesCommand>();
-        }
-
-        [Fact]
-        public void Delegate_type_activator_throws_if_the_underlying_function_returns_null()
-        {
-            // Arrange
-            var activator = new DelegateTypeActivator(_ => null);
-
-            // Act & assert
-            Assert.Throws<CliFxException>(() =>
-                activator.CreateInstance(typeof(WithDependenciesCommand)));
-        }
-    }
-}

CliFx.Tests/DirectivesSpecs.Commands.cs

@@ -1,14 +0,0 @@
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class DirectivesSpecs
-    {
-        [Command("cmd")]
-        private class NamedCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/DirectivesSpecs.cs

@@ -1,36 +1,91 @@
-using System.Collections.Generic;
+using System;
-using System.IO;
+using System.Collections.Generic;
+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;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class DirectivesSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
 {
-    public partial class DirectivesSpecs
+    [Fact(Timeout = 15000)]
-    {
+    public async Task I_can_use_the_debug_directive_to_make_the_application_wait_for_the_debugger_to_attach()
-        [Fact]
-        public async Task Preview_directive_can_be_enabled_to_print_provided_arguments_as_they_were_parsed()
     {
         // Arrange
-            await using var stdOut = new MemoryStream();
+        using var cts = new CancellationTokenSource();
-            var console = new VirtualConsole(output: stdOut);
+
+        // 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(Dummy.Program.FilePath).WithArguments("[debug]") | HandleStdOut;
+
+        // Act & assert
+        try
+        {
+            await command.ExecuteAsync(cts.Token);
+        }
+        catch (OperationCanceledException ex) when (ex.CancellationToken == cts.Token)
+        {
+            // This means that the process was killed after it wrote the expected output
+        }
+    }
+
+    [Fact]
+    public async Task I_can_use_the_preview_directive_to_make_the_application_print_the_parsed_command_input()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command("cmd")]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
-                .AddCommand(typeof(NamedCommand))
+            .AddCommand(commandType)
-                .UseConsole(console)
+            .UseConsole(FakeConsole)
             .AllowPreviewMode()
             .Build();
 
         // Act
         var exitCode = await application.RunAsync(
-                new[] {"[preview]", "cmd", "param", "-abc", "--option", "foo"},
+            ["[preview]", "cmd", "param", "-abc", "--option", "foo"],
-                new Dictionary<string, string>());
+            new Dictionary<string, string> { ["ENV_QOP"] = "hello", ["ENV_KIL"] = "world" }
-
+        );
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
         // Assert
         exitCode.Should().Be(0);
-            stdOutData.Should().ContainAll("cmd", "<param>", "[-a]", "[-b]", "[-c]", "[--option foo]");
+
-        }
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut
+            .Should()
+            .ContainAllInOrder(
+                "cmd",
+                "<param>",
+                "[-a]",
+                "[-b]",
+                "[-c]",
+                "[--option \"foo\"]",
+                "ENV_QOP",
+                "=",
+                "\"hello\"",
+                "ENV_KIL",
+                "=",
+                "\"world\""
+            );
     }
 }

CliFx.Tests/EnvironmentSpecs.cs

@@ -0,0 +1,160 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
+using CliWrap;
+using CliWrap.Buffered;
+using FluentAssertions;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace CliFx.Tests;
+
+public class EnvironmentSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
+{
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo", EnvironmentVariable = "ENV_FOO")]
+                public string? Foo { get; init; }
+
+                [CommandOption("bar", EnvironmentVariable = "ENV_BAR")]
+                public string? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    console.WriteLine(Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "42"],
+            new Dictionary<string, string> { ["ENV_FOO"] = "100", ["ENV_BAR"] = "200" }
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().ConsistOfLines("42", "200");
+    }
+
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo", EnvironmentVariable = "ENV_FOO")]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string> { ["ENV_FOO"] = $"bar{Path.PathSeparator}baz" }
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("bar", "baz");
+    }
+
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo", EnvironmentVariable = "ENV_FOO")]
+                public string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string> { ["ENV_FOO"] = $"bar{Path.PathSeparator}baz" }
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be($"bar{Path.PathSeparator}baz");
+    }
+
+    [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.
+
+        // Arrange
+        var command = Cli.Wrap(Dummy.Program.FilePath)
+            .WithArguments("env-test")
+            .WithEnvironmentVariables(e => e.Set("ENV_TARGET", "Mars"));
+
+        // Act
+        var result = await command.ExecuteBufferedAsync();
+
+        // Assert
+        result.StandardOutput.Trim().Should().Be("Hello Mars!");
+    }
+}

CliFx.Tests/EnvironmentVariablesSpecs.Commands.cs

@@ -1,27 +0,0 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class EnvironmentVariablesSpecs
-    {
-        [Command]
-        private class EnvironmentVariableCollectionCommand : ICommand
-        {
-            [CommandOption("opt", EnvironmentVariableName = "ENV_OPT")]
-            public IReadOnlyList<string>? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command]
-        private class EnvironmentVariableCommand : ICommand
-        {
-            [CommandOption("opt", EnvironmentVariableName = "ENV_OPT")]
-            public string? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/EnvironmentVariablesSpecs.cs

@@ -1,96 +0,0 @@
-using System.Collections.Generic;
-using System.IO;
-using System.Threading.Tasks;
-using CliFx.Domain;
-using CliWrap;
-using CliWrap.Buffered;
-using FluentAssertions;
-using Xunit;
-
-namespace CliFx.Tests
-{
-    public partial class EnvironmentVariablesSpecs
-    {
-        // This test uses a real application to make sure environment variables are actually read correctly
-        [Fact]
-        public async Task Option_can_use_a_specific_environment_variable_as_fallback()
-        {
-            // Arrange
-            var command = Cli.Wrap("dotnet")
-                .WithArguments(a => a
-                    .Add(Dummy.Program.Location))
-                .WithEnvironmentVariables(e => e
-                    .Set("ENV_TARGET", "Mars"));
-
-            // Act
-            var stdOut = await command.ExecuteBufferedAsync().Select(r => r.StandardOutput);
-
-            // Assert
-            stdOut.TrimEnd().Should().Be("Hello Mars!");
-        }
-
-        // This test uses a real application to make sure environment variables are actually read correctly
-        [Fact]
-        public async Task Option_only_uses_environment_variable_as_fallback_if_the_value_was_not_directly_provided()
-        {
-            // Arrange
-            var command = Cli.Wrap("dotnet")
-                .WithArguments(a => a
-                    .Add(Dummy.Program.Location)
-                    .Add("--target")
-                    .Add("Jupiter"))
-                .WithEnvironmentVariables(e => e
-                    .Set("ENV_TARGET", "Mars"));
-
-            // Act
-            var stdOut = await command.ExecuteBufferedAsync().Select(r => r.StandardOutput);
-
-            // Assert
-            stdOut.TrimEnd().Should().Be("Hello Jupiter!");
-        }
-
-        [Fact]
-        public void Option_of_non_scalar_type_can_take_multiple_separated_values_from_an_environment_variable()
-        {
-            // Arrange
-            var schema = ApplicationSchema.Resolve(new[] {typeof(EnvironmentVariableCollectionCommand)});
-
-            var input = CommandLineInput.Empty;
-            var envVars = new Dictionary<string, string>
-            {
-                ["ENV_OPT"] = $"foo{Path.PathSeparator}bar"
-            };
-
-            // Act
-            var command = schema.InitializeEntryPoint(input, envVars);
-
-            // Assert
-            command.Should().BeEquivalentTo(new EnvironmentVariableCollectionCommand
-            {
-                Option = new[] {"foo", "bar"}
-            });
-        }
-
-        [Fact]
-        public void Option_of_scalar_type_can_only_take_a_single_value_from_an_environment_variable_even_if_it_contains_separators()
-        {
-            // Arrange
-            var schema = ApplicationSchema.Resolve(new[] {typeof(EnvironmentVariableCommand)});
-
-            var input = CommandLineInput.Empty;
-            var envVars = new Dictionary<string, string>
-            {
-                ["ENV_OPT"] = $"foo{Path.PathSeparator}bar"
-            };
-
-            // Act
-            var command = schema.InitializeEntryPoint(input, envVars);
-
-            // Assert
-            command.Should().BeEquivalentTo(new EnvironmentVariableCommand
-            {
-                Option = $"foo{Path.PathSeparator}bar"
-            });
-        }
-    }
-}

CliFx.Tests/ErrorReportingSpecs.Commands.cs

@@ -1,31 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-using CliFx.Exceptions;
-
-namespace CliFx.Tests
-{
-    public partial class ErrorReportingSpecs
-    {
-        [Command("exc")]
-        private class GenericExceptionCommand : ICommand
-        {
-            [CommandOption("msg", 'm')]
-            public string? Message { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => throw new Exception(Message);
-        }
-
-        [Command("exc")]
-        private class CommandExceptionCommand : ICommand
-        {
-            [CommandOption("code", 'c')]
-            public int ExitCode { get; set; } = 1337;
-
-            [CommandOption("msg", 'm')]
-            public string? Message { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => throw new CommandException(Message, ExitCode);
-        }
-    }
-}

CliFx.Tests/ErrorReportingSpecs.cs

@@ -1,84 +1,209 @@
 using System.Collections.Generic;
-using System.IO;
 using System.Threading.Tasks;
+using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
 using FluentAssertions;
 using Xunit;
+using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class ErrorReportingSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
 {
-    public partial class ErrorReportingSpecs
-    {
     [Fact]
-        public async Task Command_may_throw_a_generic_exception_which_exits_and_prints_full_error_details()
+    public async Task I_can_throw_an_exception_in_a_command_to_report_an_error_with_a_stacktrace()
     {
         // Arrange
-            await using var stdErr = new MemoryStream();
+        var commandType = DynamicCommandBuilder.Compile(
-            var console = new VirtualConsole(error: stdErr);
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new Exception("Something went wrong");
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
-                .AddCommand(typeof(GenericExceptionCommand))
+            .AddCommand(commandType)
-                .UseConsole(console)
+            .UseConsole(FakeConsole)
             .Build();
 
         // Act
         var exitCode = await application.RunAsync(
-                new[] {"exc", "-m", "Kaput"},
+            [],
-                new Dictionary<string, string>());
+            new Dictionary<string, string>()
-
+        );
-            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
         // Assert
         exitCode.Should().NotBe(0);
-            stdErrData.Should().Contain("Kaput");
+
-            stdErrData.Length.Should().BeGreaterThan("Kaput".Length);
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().BeEmpty();
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr
+            .Should()
+            .ContainAllInOrder("System.Exception", "Something went wrong", "at", "CliFx.");
     }
 
     [Fact]
-        public async Task Command_may_throw_a_specialized_exception_which_exits_with_custom_code_and_prints_minimal_error_details()
+    public async Task I_can_throw_an_exception_with_an_inner_exception_in_a_command_to_report_an_error_with_a_stacktrace()
     {
         // Arrange
-            await using var stdErr = new MemoryStream();
+        var commandType = DynamicCommandBuilder.Compile(
-            var console = new VirtualConsole(error: stdErr);
+            // lang=csharp
+            """
+            [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(typeof(CommandExceptionCommand))
+            .AddCommand(commandType)
-                .UseConsole(console)
+            .UseConsole(FakeConsole)
             .Build();
 
         // Act
         var exitCode = await application.RunAsync(
-                new[] {"exc", "-m", "Kaput", "-c", "69"},
+            [],
-                new Dictionary<string, string>());
+            new Dictionary<string, string>()
+        );
 
-            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
+        // 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",
+                "at",
+                "CliFx."
+            );
+    }
+
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new CommandException("Something went wrong", 69);
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
 
         // Assert
         exitCode.Should().Be(69);
-            stdErrData.Should().Be("Kaput");
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().BeEmpty();
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Trim().Should().Be("Something went wrong");
     }
 
     [Fact]
-        public async Task Command_may_throw_a_specialized_exception_without_error_message_which_exits_and_prints_full_error_details()
+    public async Task I_can_throw_an_exception_without_a_message_in_a_command_to_report_an_error_with_a_stacktrace()
     {
         // Arrange
-            await using var stdErr = new MemoryStream();
+        var commandType = DynamicCommandBuilder.Compile(
-            var console = new VirtualConsole(error: stdErr);
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new CommandException("", 69);
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
-                .AddCommand(typeof(CommandExceptionCommand))
+            .AddCommand(commandType)
-                .UseConsole(console)
+            .UseConsole(FakeConsole)
             .Build();
 
         // Act
         var exitCode = await application.RunAsync(
-                new[] {"exc", "-m", "Kaput"},
+            [],
-                new Dictionary<string, string>());
+            new Dictionary<string, string>()
-
+        );
-            var stdErrData = console.Error.Encoding.GetString(stdErr.ToArray()).TrimEnd();
 
         // Assert
-            exitCode.Should().NotBe(0);
+        exitCode.Should().Be(69);
-            stdErrData.Should().NotBeEmpty();
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().BeEmpty();
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().ContainAllInOrder("CliFx.Exceptions.CommandException", "at", "CliFx.");
     }
+
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console) =>
+                    throw new CommandException("Something went wrong", 69, true);
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .SetDescription("This will be in help text")
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // 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/HelpTextSpecs.Commands.cs

@@ -1,96 +0,0 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class HelpTextSpecs
-    {
-        [Command(Description = "DefaultCommand description.")]
-        private class DefaultCommand : ICommand
-        {
-            [CommandOption("option-a", 'a', Description = "OptionA description.")]
-            public string? OptionA { get; set; }
-
-            [CommandOption("option-b", 'b', Description = "OptionB description.")]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd", Description = "NamedCommand description.")]
-        private class NamedCommand : ICommand
-        {
-            [CommandParameter(0, Name = "param-a", Description = "ParameterA description.")]
-            public string? ParameterA { get; set; }
-
-            [CommandOption("option-c", 'c', Description = "OptionC description.")]
-            public string? OptionC { get; set; }
-
-            [CommandOption("option-d", 'd', Description = "OptionD description.")]
-            public string? OptionD { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd sub", Description = "NamedSubCommand description.")]
-        private class NamedSubCommand : ICommand
-        {
-            [CommandParameter(0, Name = "param-b", Description = "ParameterB description.")]
-            public string? ParameterB { get; set; }
-
-            [CommandParameter(1, Name = "param-c", Description = "ParameterC description.")]
-            public string? ParameterC { get; set; }
-
-            [CommandOption("option-e", 'e', Description = "OptionE description.")]
-            public string? OptionE { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-params")]
-        private class ParametersCommand : ICommand
-        {
-            [CommandParameter(0, Name = "first")]
-            public string? ParameterA { get; set; }
-
-            [CommandParameter(10)]
-            public int? ParameterB { get; set; }
-
-            [CommandParameter(20, Description = "A list of numbers", Name = "third list")]
-            public IEnumerable<int>? ParameterC { get; set; }
-
-            [CommandOption("option", 'o')]
-            public string? Option { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-req-opts")]
-        private class RequiredOptionsCommand : ICommand
-        {
-            [CommandOption("option-f", 'f', IsRequired = true)]
-            public string? OptionF { get; set; }
-
-            [CommandOption("option-g", 'g', IsRequired = true)]
-            public IEnumerable<int>? OptionG { get; set; }
-
-            [CommandOption("option-h", 'h')]
-            public string? OptionH { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-
-        [Command("cmd-with-env-vars")]
-        private class EnvironmentVariableCommand : ICommand
-        {
-            [CommandOption("option-a", 'a', IsRequired = true, EnvironmentVariableName = "ENV_OPT_A")]
-            public string? OptionA { get; set; }
-
-            [CommandOption("option-b", 'b', EnvironmentVariableName = "ENV_OPT_B")]
-            public string? OptionB { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console) => default;
-        }
-    }
-}

CliFx.Tests/OptionBindingSpecs.cs

@@ -0,0 +1,762 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
+using FluentAssertions;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace CliFx.Tests;
+
+public class OptionBindingSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
+{
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_and_get_the_value_from_the_corresponding_argument_by_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public bool Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["--foo"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("True");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_and_get_the_value_from_the_corresponding_argument_by_short_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public bool Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["-f"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("True");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_and_get_the_value_from_the_corresponding_argument_set_by_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+
+                [CommandOption("bar")]
+                public string? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "one", "--bar", "two"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = one", "Bar = two");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_and_get_the_value_from_the_corresponding_argument_set_by_short_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+
+                [CommandOption('b')]
+                public string? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "one", "-b", "two"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = one", "Bar = two");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_and_get_the_value_from_the_corresponding_argument_stack_by_short_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public string? Foo { get; init; }
+
+                [CommandOption('b')]
+                public string? Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-fb", "value"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = ", "Bar = value");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_non_scalar_property_and_get_the_values_from_the_corresponding_arguments_by_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("Foo")]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "one", "two", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_non_scalar_property_and_get_the_values_from_the_corresponding_arguments_by_short_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "one", "two", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_non_scalar_property_and_get_the_values_from_the_corresponding_argument_sets_by_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "one", "--foo", "two", "--foo", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_non_scalar_property_and_get_the_values_from_the_corresponding_argument_sets_by_short_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption('f')]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["-f", "one", "-f", "two", "-f", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_non_scalar_property_and_get_the_values_from_the_corresponding_argument_sets_by_name_or_short_name()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo", 'f')]
+                public IReadOnlyList<string>? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    foreach (var i in Foo)
+                        console.WriteLine(i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "one", "-f", "two", "--foo", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("one", "two", "three");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_and_get_no_value_if_the_user_does_not_provide_the_corresponding_argument()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+
+                [CommandOption("bar")]
+                public string? Bar { get; init; } = "hello";
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "one"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = one", "Bar = hello");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_through_multiple_inheritance()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            public static class SharedContext
+            {
+                public static int Foo { get; set; }
+
+                public static bool Bar { get; set; }
+            }
+
+            public interface IHasFoo : ICommand
+            {
+                [CommandOption("foo")]
+                public int Foo
+                {
+                    get => SharedContext.Foo;
+                    init => SharedContext.Foo = value;
+                }
+            }
+
+            public interface IHasBar : ICommand
+            {
+                [CommandOption("bar")]
+                public bool Bar
+                {
+                    get => SharedContext.Bar;
+                    init => SharedContext.Bar = value;
+                }
+            }
+
+            public interface IHasBaz : ICommand
+            {
+                public string? Baz { get; init; }
+            }
+
+            [Command]
+            public class Command : IHasFoo, IHasBar, IHasBaz
+            {
+                [CommandOption("baz")]
+                public string? Baz { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + SharedContext.Foo);
+                    console.WriteLine("Bar = " + SharedContext.Bar);
+                    console.WriteLine("Baz = " + Baz);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["--foo", "42", "--bar", "--baz", "xyz"]);
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = 42", "Bar = True", "Baz = xyz");
+    }
+
+    [Fact]
+    public async Task I_can_bind_an_option_to_a_property_and_get_the_correct_value_if_the_user_provides_an_argument_containing_a_negative_number()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(Foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "-13"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("-13");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_required_option_to_a_property_and_get_an_error_if_the_user_does_not_provide_the_corresponding_argument()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public required string Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Missing required option(s)");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_required_option_to_a_property_and_get_an_error_if_the_user_provides_an_empty_argument()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public required string Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["--foo"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Missing required option(s)");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_an_option_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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public required IReadOnlyList<string> Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["--foo"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Missing required option(s)");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_options_and_get_an_error_if_the_user_provides_unrecognized_arguments()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "one", "--bar", "two"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Unrecognized option(s)");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_an_option_to_a_scalar_property_and_get_an_error_if_the_user_provides_too_many_arguments()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandOption("foo")]
+                public string? Foo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["--foo", "one", "two", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("expects a single argument, but provided with multiple");
+    }
+}

CliFx.Tests/ParameterBindingSpecs.cs

@@ -0,0 +1,263 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
+using FluentAssertions;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace CliFx.Tests;
+
+public class ParameterBindingSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
+{
+    [Fact]
+    public async Task I_can_bind_a_parameter_to_a_property_and_get_the_value_from_the_corresponding_argument()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["one", "two"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = one", "Bar = two");
+    }
+
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                [CommandParameter(1)]
+                public required string Bar { get; init; }
+
+                [CommandParameter(2)]
+                public required IReadOnlyList<string> Baz { get; init; }
+
+                [CommandOption("boo")]
+                public string? Boo { get; init; }
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    foreach (var i in Baz)
+                        console.WriteLine("Baz = " + i);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            ["one", "two", "three", "four", "five", "--boo", "xxx"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut
+            .Should()
+            .ConsistOfLines("Foo = one", "Bar = two", "Baz = three", "Baz = four", "Baz = five");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_a_parameter_to_a_property_and_get_an_error_if_the_user_does_not_provide_the_corresponding_argument()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                [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(["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_try_to_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(
+            // lang=csharp
+            """
+            [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(["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(
+            // lang=csharp
+            """
+            [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.WriteLine("Foo = " + Foo);
+                    console.WriteLine("Bar = " + Bar);
+
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(["abc"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Should().ConsistOfLines("Foo = abc", "Bar = xyz");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_bind_parameters_and_get_an_error_if_the_user_provides_too_many_arguments()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                [CommandParameter(0)]
+                public required string Foo { get; init; }
+
+                [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(
+            ["one", "two", "three"],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Unexpected parameter(s)");
+    }
+}

CliFx.Tests/RoutingSpecs.Commands.cs

@@ -1,51 +0,0 @@
-using System.Collections.Generic;
-using System.Threading.Tasks;
-using CliFx.Attributes;
-
-namespace CliFx.Tests
-{
-    public partial class RoutingSpecs
-    {
-        [Command]
-        private class DefaultCommand : ICommand
-        {
-            public ValueTask ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine("Hello world!");
-                return default;
-            }
-        }
-
-        [Command("concat", Description = "Concatenate strings.")]
-        private class ConcatCommand : ICommand
-        {
-            [CommandOption('i', IsRequired = true, Description = "Input strings.")]
-            public IReadOnlyList<string> Inputs { get; set; }
-
-            [CommandOption('s', Description = "String separator.")]
-            public string Separator { get; set; } = "";
-
-            public ValueTask ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine(string.Join(Separator, Inputs));
-                return default;
-            }
-        }
-
-        [Command("div", Description = "Divide one number by another.")]
-        private class DivideCommand : ICommand
-        {
-            [CommandOption("dividend", 'D', IsRequired = true, Description = "The number to divide.")]
-            public double Dividend { get; set; }
-
-            [CommandOption("divisor", 'd', IsRequired = true, Description = "The number to divide by.")]
-            public double Divisor { get; set; }
-
-            public ValueTask ExecuteAsync(IConsole console)
-            {
-                console.Output.WriteLine(Dividend / Divisor);
-                return default;
-            }
-        }
-    }
-}

CliFx.Tests/RoutingSpecs.cs

@@ -1,90 +1,179 @@
-using System;
+using System.Collections.Generic;
-using System.Collections.Generic;
-using System.IO;
 using System.Threading.Tasks;
+using CliFx.Tests.Utils;
 using FluentAssertions;
 using Xunit;
+using Xunit.Abstractions;
 
-namespace CliFx.Tests
+namespace CliFx.Tests;
+
+public class RoutingSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
 {
-    public partial class RoutingSpecs
-    {
     [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
-            await using var stdOut = new MemoryStream();
+        var commandTypes = DynamicCommandBuilder.CompileMany(
-            var console = new VirtualConsole(output: stdOut);
+            // lang=csharp
+            """
+            [Command]
+            public class DefaultCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("default");
+                    return default;
+                }
+            }
+
+            [Command("cmd")]
+            public class NamedCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("cmd");
+                    return default;
+                }
+            }
+
+            [Command("cmd child")]
+            public class NamedChildCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("cmd child");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
+            .AddCommands(commandTypes)
-                .AddCommand(typeof(ConcatCommand))
+            .UseConsole(FakeConsole)
-                .AddCommand(typeof(DivideCommand))
-                .UseConsole(console)
             .Build();
 
         // Act
         var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            [],
-                new Dictionary<string, string>());
+            new Dictionary<string, string>()
-
+        );
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
         // Assert
         exitCode.Should().Be(0);
-            stdOutData.Should().Be("Hello world!");
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("default");
     }
 
     [Fact]
-        public async Task Help_text_is_printed_if_no_arguments_were_provided_and_default_command_is_not_defined()
+    public async Task I_can_configure_a_command_to_be_executed_when_the_user_specifies_its_name()
     {
         // Arrange
-            await using var stdOut = new MemoryStream();
+        var commandTypes = DynamicCommandBuilder.CompileMany(
-            var console = new VirtualConsole(output: stdOut);
+            // lang=csharp
+            """
+            [Command]
+            public class DefaultCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("default");
+                    return default;
+                }
+            }
+
+            [Command("cmd")]
+            public class NamedCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("cmd");
+                    return default;
+                }
+            }
+
+            [Command("cmd child")]
+            public class NamedChildCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("cmd child");
+                    return default;
+                }
+            }
+            """
+        );
 
         var application = new CliApplicationBuilder()
-                .AddCommand(typeof(ConcatCommand))
+            .AddCommands(commandTypes)
-                .AddCommand(typeof(DivideCommand))
+            .UseConsole(FakeConsole)
-                .UseConsole(console)
+            .Build();
-                .UseDescription("This will be visible in help")
+
+        // Act
+        var exitCode = await application.RunAsync(["cmd"], new Dictionary<string, string>());
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("cmd");
+    }
+
+    [Fact]
+    public async Task I_can_configure_a_nested_command_to_be_executed_when_the_user_specifies_its_name()
+    {
+        // Arrange
+        var commandTypes = DynamicCommandBuilder.CompileMany(
+            // lang=csharp
+            """
+            [Command]
+            public class DefaultCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("default");
+                    return default;
+                }
+            }
+
+            [Command("cmd")]
+            public class NamedCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("cmd");
+                    return default;
+                }
+            }
+
+            [Command("cmd child")]
+            public class NamedChildCommand : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("cmd child");
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommands(commandTypes)
+            .UseConsole(FakeConsole)
             .Build();
 
         // Act
         var exitCode = await application.RunAsync(
-                Array.Empty<string>(),
+            ["cmd", "child"],
-                new Dictionary<string, string>());
+            new Dictionary<string, string>()
-
+        );
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
 
         // Assert
         exitCode.Should().Be(0);
-            stdOutData.Should().Contain("This will be visible in help");
-        }
 
-        [Fact]
+        var stdOut = FakeConsole.ReadOutputString();
-        public async Task Specific_named_command_is_executed_if_provided_arguments_match_its_name()
+        stdOut.Trim().Should().Be("cmd child");
-        {
-            // Arrange
-            await using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultCommand))
-                .AddCommand(typeof(ConcatCommand))
-                .AddCommand(typeof(DivideCommand))
-                .UseConsole(console)
-                .Build();
-
-            // Act
-            var exitCode = await application.RunAsync(
-                new[] {"concat", "-i", "foo", "bar", "-s", ", "},
-                new Dictionary<string, string>());
-
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray()).TrimEnd();
-
-            // Assert
-            exitCode.Should().Be(0);
-            stdOutData.Should().Be("foo, bar");
-        }
     }
 }

CliFx.Tests/SpecsBase.cs

@@ -0,0 +1,19 @@
+using System;
+using CliFx.Infrastructure;
+using CliFx.Tests.Utils.Extensions;
+using Xunit.Abstractions;
+
+namespace CliFx.Tests;
+
+public abstract class SpecsBase(ITestOutputHelper testOutput) : IDisposable
+{
+    public ITestOutputHelper TestOutput { get; } = testOutput;
+
+    public FakeInMemoryConsole FakeConsole { get; } = new();
+
+    public void Dispose()
+    {
+        FakeConsole.DumpToTestOutput(TestOutput);
+        FakeConsole.Dispose();
+    }
+}

CliFx.Tests/TypeActivationSpecs.cs

@@ -0,0 +1,223 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using CliFx.Infrastructure;
+using CliFx.Tests.Utils;
+using FluentAssertions;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace CliFx.Tests;
+
+public class TypeActivationSpecs(ITestOutputHelper testOutput) : SpecsBase(testOutput)
+{
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("foo");
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(new DefaultTypeActivator())
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("foo");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public Command(string foo) {}
+
+                public ValueTask ExecuteAsync(IConsole console) => default;
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(new DefaultTypeActivator())
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().NotBe(0);
+
+        var stdErr = FakeConsole.ReadErrorString();
+        stdErr.Should().Contain("Failed to create an instance of type");
+    }
+
+    [Fact]
+    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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                private readonly string _foo;
+
+                public Command(string foo) => _foo = foo;
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(_foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(type => Activator.CreateInstance(type, "Hello world")!)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // 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_to_initialize_types_using_a_service_provider()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                private readonly string _foo;
+
+                public Command(string foo) => _foo = foo;
+
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine(_foo);
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(commandTypes =>
+            {
+                var services = new ServiceCollection();
+
+                foreach (var serviceType in commandTypes)
+                {
+                    services.AddSingleton(
+                        serviceType,
+                        Activator.CreateInstance(serviceType, "Hello world")!
+                    );
+                }
+
+                return services.BuildServiceProvider();
+            })
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            new Dictionary<string, string>()
+        );
+
+        // Assert
+        exitCode.Should().Be(0);
+
+        var stdOut = FakeConsole.ReadOutputString();
+        stdOut.Trim().Should().Be("Hello world");
+    }
+
+    [Fact]
+    public async Task I_can_try_to_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(
+            // lang=csharp
+            """
+            [Command]
+            public class Command : ICommand
+            {
+                public ValueTask ExecuteAsync(IConsole console)
+                {
+                    console.WriteLine("foo");
+                    return default;
+                }
+            }
+            """
+        );
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator((Type _) => null!)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            [],
+            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/UtilitiesSpecs.cs

@@ -1,54 +0,0 @@
-using System.IO;
-using System.Linq;
-using CliFx.Utilities;
-using FluentAssertions;
-using Xunit;
-
-namespace CliFx.Tests
-{
-    public class UtilitiesSpecs
-    {
-        [Fact]
-        public void Progress_ticker_can_be_used_to_report_progress_to_console()
-        {
-            // Arrange
-            using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut, isOutputRedirected: false);
-
-            var ticker = console.CreateProgressTicker();
-
-            var progressValues = Enumerable.Range(0, 100).Select(p => p / 100.0).ToArray();
-            var progressStringValues = progressValues.Select(p => p.ToString("P2")).ToArray();
-
-            // Act
-            foreach (var progress in progressValues)
-                ticker.Report(progress);
-
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray());
-
-            // Assert
-            stdOutData.Should().ContainAll(progressStringValues);
-        }
-
-        [Fact]
-        public void Progress_ticker_does_not_write_to_console_if_output_is_redirected()
-        {
-            // Arrange
-            using var stdOut = new MemoryStream();
-            var console = new VirtualConsole(output: stdOut);
-
-            var ticker = console.CreateProgressTicker();
-
-            var progressValues = Enumerable.Range(0, 100).Select(p => p / 100.0).ToArray();
-
-            // Act
-            foreach (var progress in progressValues)
-                ticker.Report(progress);
-
-            var stdOutData = console.Output.Encoding.GetString(stdOut.ToArray());
-
-            // Assert
-            stdOutData.Should().BeEmpty();
-        }
-    }
-}

CliFx.Tests/Utils/DynamicCommandBuilder.cs

@@ -0,0 +1,135 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Basic.Reference.Assemblies;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.Text;
+
+namespace CliFx.Tests.Utils;
+
+// This class uses Roslyn to compile commands dynamically.
+// It allows us to collocate commands with tests more easily, which helps a lot when reasoning about them.
+// Unfortunately, this comes at a cost of static typing, but this is still a worthwhile trade off.
+// Maybe one day C# will allow declaring classes inside methods and doing this will no longer be necessary.
+// Language proposal: https://github.com/dotnet/csharplang/discussions/130
+internal static class DynamicCommandBuilder
+{
+    public static IReadOnlyList<Type> CompileMany(string sourceCode)
+    {
+        // Get default system namespaces
+        var defaultSystemNamespaces = new[]
+        {
+            "System",
+            "System.Collections",
+            "System.Collections.Generic",
+            "System.Linq",
+            "System.Threading.Tasks",
+            "System.Globalization",
+        };
+
+        // Get default CliFx namespaces
+        var defaultCliFxNamespaces = typeof(ICommand)
+            .Assembly.GetTypes()
+            .Where(t => t.IsPublic)
+            .Select(t => t.Namespace)
+            .Distinct()
+            .ToArray();
+
+        // Append default imports to the source code
+        var sourceCodeWithUsings =
+            string.Join(Environment.NewLine, defaultSystemNamespaces.Select(n => $"using {n};"))
+            + string.Join(Environment.NewLine, defaultCliFxNamespaces.Select(n => $"using {n};"))
+            + Environment.NewLine
+            + sourceCode;
+
+        // Parse the source code
+        var ast = SyntaxFactory.ParseSyntaxTree(
+            SourceText.From(sourceCodeWithUsings),
+            CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.Preview)
+        );
+
+        // Compile the code to IL
+        var compilation = CSharpCompilation.Create(
+            "CliFxTests_DynamicAssembly_" + Guid.NewGuid(),
+            [ast],
+            Net80
+                .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
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
+        );
+
+        var compilationErrors = compilation
+            .GetDiagnostics()
+            .Where(d => d.Severity >= DiagnosticSeverity.Error)
+            .ToArray();
+
+        if (compilationErrors.Any())
+        {
+            throw new InvalidOperationException(
+                $"""
+                Failed to compile code.
+                {string.Join(Environment.NewLine, compilationErrors.Select(e => e.ToString()))}
+                """
+            );
+        }
+
+        // Emit the code to an in-memory buffer
+        using var buffer = new MemoryStream();
+        var emit = compilation.Emit(buffer);
+
+        var emitErrors = emit
+            .Diagnostics.Where(d => d.Severity >= DiagnosticSeverity.Error)
+            .ToArray();
+
+        if (emitErrors.Any())
+        {
+            throw new InvalidOperationException(
+                $"""
+                Failed to emit code.
+                {string.Join(Environment.NewLine, emitErrors.Select(e => e.ToString()))}
+                """
+            );
+        }
+
+        // Load the generated assembly
+        var generatedAssembly = Assembly.Load(buffer.ToArray());
+
+        // Return all defined commands
+        var commandTypes = generatedAssembly
+            .GetTypes()
+            .Where(t => t.IsAssignableTo(typeof(ICommand)) && !t.IsAbstract)
+            .ToArray();
+
+        if (commandTypes.Length <= 0)
+        {
+            throw new InvalidOperationException(
+                "There are no command definitions in the provided source code."
+            );
+        }
+
+        return commandTypes;
+    }
+
+    public static Type Compile(string sourceCode)
+    {
+        var commandTypes = CompileMany(sourceCode);
+        if (commandTypes.Count > 1)
+        {
+            throw new InvalidOperationException(
+                "There are more than one command definitions in the provided source code."
+            );
+        }
+
+        return commandTypes.Single();
+    }
+}

CliFx.Tests/Utils/Extensions/AssertionExtensions.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using FluentAssertions;
+using FluentAssertions.Primitives;
+
+namespace CliFx.Tests.Utils.Extensions;
+
+internal static class AssertionExtensions
+{
+    public static void ConsistOfLines(
+        this StringAssertions assertions,
+        params IEnumerable<string> lines
+    ) =>
+        assertions
+            .Subject.Split(['\n', '\r'], StringSplitOptions.RemoveEmptyEntries)
+            .Should()
+            .Equal(lines);
+
+    public static AndConstraint<StringAssertions> ContainAllInOrder(
+        this StringAssertions assertions,
+        IEnumerable<string> values
+    )
+    {
+        var lastIndex = 0;
+
+        foreach (var value in values)
+        {
+            var index = assertions.Subject.IndexOf(value, lastIndex, StringComparison.Ordinal);
+
+            if (index < 0)
+            {
+                assertions.CurrentAssertionChain.FailWith(
+                    $"Expected string '{assertions.Subject}' to contain '{value}' after position {lastIndex}."
+                );
+            }
+
+            lastIndex = index;
+        }
+
+        return new AndConstraint<StringAssertions>(assertions);
+    }
+
+    public static AndConstraint<StringAssertions> ContainAllInOrder(
+        this StringAssertions assertions,
+        params string[] values
+    ) => assertions.ContainAllInOrder((IEnumerable<string>)values);
+}

CliFx.Tests/Utils/Extensions/ConsoleExtensions.cs

@@ -0,0 +1,19 @@
+using CliFx.Infrastructure;
+using Xunit.Abstractions;
+
+namespace CliFx.Tests.Utils.Extensions;
+
+internal static class ConsoleExtensions
+{
+    public static void DumpToTestOutput(
+        this FakeInMemoryConsole console,
+        ITestOutputHelper testOutput
+    )
+    {
+        testOutput.WriteLine("[*] Captured standard output:");
+        testOutput.WriteLine(console.ReadOutputString());
+
+        testOutput.WriteLine("[*] Captured standard error:");
+        testOutput.WriteLine(console.ReadErrorString());
+    }
+}

CliFx.Tests/Utils/NoOpCommand.cs

@@ -0,0 +1,11 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Infrastructure;
+
+namespace CliFx.Tests.Utils;
+
+[Command]
+internal class NoOpCommand : ICommand
+{
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}

CliFx.props

@@ -1,11 +0,0 @@
-<Project>
-
-  <PropertyGroup>
-    <Version>1.1</Version>
-    <Company>Tyrrrz</Company>
-    <Copyright>Copyright (C) Alexey Golub</Copyright>
-    <LangVersion>latest</LangVersion>
-    <Nullable>enable</Nullable>
-  </PropertyGroup>
-
-</Project>