Update version

Fixes #104

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -0,0 +1,30 @@
+name: "\U0001F41E Bug report"
+description: Report broken functionality.
+labels: [bug]
+body:
+- type: markdown
+  attributes:
+    value: |
+      - Please check existing issues (both opened and closed) to ensure that this bug hasn't been reported before.
+      - If you want to ask a question instead of reporting a bug, use [discussions](https://github.com/Tyrrrz/CliFx/discussions/new) instead.
+
+- type: input
+  attributes:
+    label: Version
+    description: "Which version(s) of CliFx does this bug affect?"
+  validations:
+    required: true
+
+- type: textarea
+  attributes:
+    label: Details
+    description: "Clear and thorough explanation of the bug. If relevant, include screenshots or screen recordings."
+  validations:
+    required: true
+
+- type: textarea
+  attributes:
+    label: Steps to reproduce
+    description: "Minimum steps or code required to reproduce the bug."
+  validations:
+    required: true

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: false
+contact_links:
+  - name: "\U0001F5E8 Ask a question"
+    url: https://github.com/Tyrrrz/CliFx/discussions/new
+    about: Please ask and answer questions here.  

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -0,0 +1,16 @@
+name: "\U00002728 Feature request"
+description: Request a new feature.
+labels: [enhancement]
+body:
+- type: markdown
+  attributes:
+    value: |
+      - Please check existing issues (both opened and closed) to ensure that this feature hasn't been requested before.
+      - If you want to ask a question instead of requesting a feature, use [**discussions**](https://github.com/Tyrrrz/CliFx/discussions/new) instead.
+
+- type: textarea
+  attributes:
+    label: Details
+    description: "Clear and thorough explanation of the feature you have in mind."
+  validations:
+    required: true

.github/workflows/CD.yml

@@ -19,9 +19,7 @@ jobs:
           dotnet-version: 5.0.x
 
       - name: Pack
-        run: |
-          dotnet nuget locals all --clear
-          dotnet pack CliFx --configuration Release
+        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

@@ -20,9 +20,7 @@ jobs:
           dotnet-version: 5.0.x
 
       - name: Build & test
-        run: |
-          dotnet nuget locals all --clear
-          dotnet test --configuration Release --logger GitHubActions
+        run: dotnet test --configuration Release --logger GitHubActions
 
       - name: Upload coverage
         uses: codecov/codecov-action@v1.0.5

Changelog.md

@@ -1,3 +1,10 @@
+### v2.0.4 (24-Apr-2021)
+
+- Fixed an issue where output and error streams in `SystemConsole` defaulted to UTF8 encoding with BOM when the application was running with UTF8 codepage. `ConsoleWriter` will now discard preamble from the specified encoding. This fix brings the behavior of `SystemConsole` in line with .NET's own `System.Console` which also discards preamble for output and error streams.
+- Fixed an issue where help text tried to show default values for parameters and options whose type does not override `ToString()` method.
+- Fixed an issue where help text didn't show default values for parameters and options whose type is an enumerable of nullable enums. (Thanks [@Robert Dailey](https://github.com/rcdailey))
+- Fixed an issue where specific parts of the help text weren't legible in some terminals due to low color resolution. Removed the usage of `ConsoleColor.DarkGray` in help text.
+
 ### v2.0.3 (09-Apr-2021)
 
 - Improved help text by showing valid values for non-scalar enum parameters and options. (Thanks [@Robert Dailey](https://github.com/rcdailey))

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

@@ -15,7 +15,7 @@
   <ItemGroup>
     <PackageReference Include="GitHubActionsTestLogger" Version="1.2.0" />
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.4.0" />
     <PackageReference Include="xunit" Version="2.4.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" PrivateAssets="all" />

CliFx.Benchmarks/CliFx.Benchmarks.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.12.0" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.12.1" />
     <PackageReference Include="clipr" Version="1.6.1" />
     <PackageReference Include="Cocona" Version="1.5.0" />
     <PackageReference Include="CommandLineParser" Version="2.8.0" />

CliFx.Demo/CliFx.Demo.csproj

@@ -7,7 +7,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="5.0.1" />
-    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
   </ItemGroup>
 
   <ItemGroup>

CliFx.Demo/Domain/LibraryProvider.cs

@@ -21,7 +21,7 @@ namespace CliFx.Demo.Domain
 
             var data = File.ReadAllText(StorageFilePath);
 
-            return JsonConvert.DeserializeObject<Library>(data);
+            return JsonConvert.DeserializeObject<Library>(data) ?? Library.Empty;
         }
 
         public Book? TryGetBook(string title) => GetLibrary().Books.FirstOrDefault(b => b.Title == title);

CliFx.Tests/CliFx.Tests.csproj

@@ -13,11 +13,11 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="CliWrap" Version="3.3.1" />
+    <PackageReference Include="CliWrap" Version="3.3.2" />
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="GitHubActionsTestLogger" Version="1.2.0" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.4.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" PrivateAssets="all" />
     <PackageReference Include="coverlet.msbuild" Version="3.0.3" PrivateAssets="all" />

CliFx.Tests/HelpTextSpecs.cs

@@ -590,10 +590,55 @@ public enum CustomEnum { One, Two, Three }
 public class Command : ICommand
 {
     [CommandParameter(0)]
-    public List<CustomEnum> Foo { get; set; }
+    public IReadOnlyList<CustomEnum> Foo { get; set; }
 
     [CommandOption(""bar"")]
-    public List<CustomEnum> Bar { get; set; }
+    public IReadOnlyList<CustomEnum> Bar { get; set; }
+
+    public ValueTask ExecuteAsync(IConsole console) => default;
+}
+");
+
+            var application = new CliApplicationBuilder()
+                .AddCommand(commandType)
+                .UseConsole(FakeConsole)
+                .Build();
+
+            // Act
+            var exitCode = await application.RunAsync(
+                new[] {"--help"},
+                new Dictionary<string, string>()
+            );
+
+            var stdOut = FakeConsole.ReadOutputString();
+
+            // Assert
+            exitCode.Should().Be(0);
+            stdOut.Should().ContainAllInOrder(
+                "PARAMETERS",
+                "foo", "Choices:", "One", "Two", "Three",
+                "OPTIONS",
+                "--bar", "Choices:", "One", "Two", "Three"
+            );
+        }
+
+        [Fact]
+        public async Task Help_text_shows_all_valid_values_for_nullable_enum_parameters_and_options()
+        {
+            // Arrange
+            var commandType = DynamicCommandBuilder.Compile(
+                // language=cs
+                @"
+public enum CustomEnum { One, Two, Three }
+
+[Command]
+public class Command : ICommand
+{
+    [CommandParameter(0)]
+    public CustomEnum? Foo { get; set; }
+
+    [CommandOption(""bar"")]
+    public IReadOnlyList<CustomEnum?> Bar { get; set; }
 
     public ValueTask ExecuteAsync(IConsole console) => default;
 }

CliFx/Formatting/CommandInputConsoleFormatter.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Linq;
 using CliFx.Infrastructure;
 using CliFx.Input;
 
@@ -47,9 +46,9 @@ namespace CliFx.Formatting
                 foreach (var value in optionInput.Values)
                 {
                     Write(' ');
-                    Write(ConsoleColor.DarkGray, '"');
+                    Write('"');
                     Write(value);
-                    Write(ConsoleColor.DarkGray, '"');
+                    Write('"');
                 }
 
                 Write(']');
@@ -75,9 +74,9 @@ namespace CliFx.Formatting
                 Write('=');
 
                 // Value
-                Write(ConsoleColor.DarkGray, '"');
+                Write('"');
                 Write(environmentVariableInput.Value);
-                Write(ConsoleColor.DarkGray, '"');
+                Write('"');
 
                 WriteLine();
             }

CliFx/Formatting/ExceptionConsoleFormatter.cs

@@ -19,7 +19,7 @@ namespace CliFx.Formatting
             Write("at ");
 
             // Fully qualified method name
-            Write(ConsoleColor.DarkGray, stackFrame.ParentType + '.');
+            Write(stackFrame.ParentType + '.');
             Write(ConsoleColor.Yellow, stackFrame.MethodName);
 
             // Method parameters
@@ -60,7 +60,7 @@ namespace CliFx.Formatting
                 Write("in ");
 
                 // File path
-                Write(ConsoleColor.DarkGray, stackFrameDirectoryPath);
+                Write(stackFrameDirectoryPath);
                 Write(ConsoleColor.Yellow, stackFrameFileName);
 
                 // Source position
@@ -80,7 +80,7 @@ namespace CliFx.Formatting
 
             // Fully qualified exception type
             var exceptionType = exception.GetType();
-            Write(ConsoleColor.DarkGray, exceptionType.Namespace + '.');
+            Write(exceptionType.Namespace + '.');
             Write(ConsoleColor.White, exceptionType.Name);
             Write(": ");
 

CliFx/Formatting/HelpConsoleFormatter.cs

@@ -27,7 +27,7 @@ namespace CliFx.Formatting
 
         private void WriteCommandInvocation()
         {
-            Write(ConsoleColor.DarkGray, _context.ApplicationMetadata.ExecutableName);
+            Write(_context.ApplicationMetadata.ExecutableName);
 
             // Command name
             if (!string.IsNullOrWhiteSpace(_context.CommandSchema.Name))
@@ -190,9 +190,9 @@ namespace CliFx.Formatting
                             Write(", ");
                         }
 
-                        Write(ConsoleColor.DarkGray, '"');
+                        Write('"');
                         Write(validValue.ToString());
-                        Write(ConsoleColor.DarkGray, '"');
+                        Write('"');
                     }
 
                     Write('.');
@@ -269,9 +269,9 @@ namespace CliFx.Formatting
                             Write(", ");
                         }
 
-                        Write(ConsoleColor.DarkGray, '"');
+                        Write('"');
                         Write(validValue.ToString());
-                        Write(ConsoleColor.DarkGray, '"');
+                        Write('"');
                     }
 
                     Write('.');
@@ -317,10 +317,12 @@ namespace CliFx.Formatting
                                         Write(", ");
                                     }
 
-                                    Write(ConsoleColor.DarkGray, '"');
+                                    Write('"');
                                     Write(element.ToString(CultureInfo.InvariantCulture));
-                                    Write(ConsoleColor.DarkGray, '"');
+                                    Write('"');
                                 }
+
+                                Write('.');
                             }
                         }
                         else
@@ -329,13 +331,12 @@ namespace CliFx.Formatting
                             {
                                 Write(ConsoleColor.White, "Default: ");
 
-                                Write(ConsoleColor.DarkGray, '"');
+                                Write('"');
                                 Write(defaultValue.ToString(CultureInfo.InvariantCulture));
-                                Write(ConsoleColor.DarkGray, '"');
+                                Write('"');
+                                Write('.');
                             }
                         }
-
-                        Write('.');
                     }
                 }
 

CliFx/Infrastructure/ConsoleReader.cs

@@ -17,7 +17,7 @@ namespace CliFx.Infrastructure
         /// Initializes an instance of <see cref="ConsoleReader"/>.
         /// </summary>
         public ConsoleReader(IConsole console, Stream stream, Encoding encoding)
-            : base(stream, encoding, false)
+            : base(stream, encoding, false, 4096)
         {
             Console = console;
         }
@@ -33,7 +33,11 @@ namespace CliFx.Infrastructure
 
     public partial class ConsoleReader
     {
-        internal static ConsoleReader Create(IConsole console, Stream? stream) =>
-            new(console, stream is not null ? Stream.Synchronized(stream) : Stream.Null);
+        internal static ConsoleReader Create(IConsole console, Stream? stream) => new(
+            console,
+            stream is not null
+                ? Stream.Synchronized(stream)
+                : Stream.Null
+        );
     }
 }

CliFx/Infrastructure/ConsoleWriter.cs

@@ -1,5 +1,6 @@
 using System.IO;
 using System.Text;
+using CliFx.Utils;
 
 namespace CliFx.Infrastructure
 {
@@ -17,7 +18,7 @@ namespace CliFx.Infrastructure
         /// Initializes an instance of <see cref="ConsoleWriter"/>.
         /// </summary>
         public ConsoleWriter(IConsole console, Stream stream, Encoding encoding)
-            : base(stream, encoding)
+            : base(stream, encoding, 256)
         {
             Console = console;
         }
@@ -26,14 +27,18 @@ namespace CliFx.Infrastructure
         /// Initializes an instance of <see cref="ConsoleWriter"/>.
         /// </summary>
         public ConsoleWriter(IConsole console, Stream stream)
-            : this(console, stream, System.Console.OutputEncoding)
+            : this(console, stream, System.Console.OutputEncoding.WithoutPreamble())
         {
         }
     }
 
     public partial class ConsoleWriter
     {
-        internal static ConsoleWriter Create(IConsole console, Stream? stream) =>
-            new(console, stream is not null ? Stream.Synchronized(stream) : Stream.Null) {AutoFlush = true};
+        internal static ConsoleWriter Create(IConsole console, Stream? stream) => new(
+            console,
+            stream is not null
+                ? Stream.Synchronized(stream)
+                : Stream.Null
+        ) {AutoFlush = true};
     }
 }

CliFx/Schema/BindablePropertyDescriptor.cs

@@ -21,10 +21,20 @@ namespace CliFx.Schema
 
         public IReadOnlyList<object?> GetValidValues()
         {
-            var underlyingType =
-                Type.TryGetNullableUnderlyingType() ??
-                Type.TryGetEnumerableUnderlyingType() ??
-                Type;
+            static Type GetUnderlyingType(Type type)
+            {
+                var enumerableUnderlyingType = type.TryGetEnumerableUnderlyingType();
+                if (enumerableUnderlyingType is not null)
+                    return GetUnderlyingType(enumerableUnderlyingType);
+
+                var nullableUnderlyingType = type.TryGetNullableUnderlyingType();
+                if (nullableUnderlyingType is not null)
+                    return GetUnderlyingType(nullableUnderlyingType);
+
+                return type;
+            }
+            
+            var underlyingType = GetUnderlyingType(Type);
 
             // We can only get valid values for enums
             if (underlyingType.IsEnum)

CliFx/Utils/Extensions/TypeExtensions.cs

@@ -54,9 +54,11 @@ namespace CliFx.Utils.Extensions
             return array;
         }
 
-        public static bool IsToStringOverriden(this Type type) =>
-            type.GetMethod(nameof(ToString), Type.EmptyTypes) !=
-            typeof(object).GetMethod(nameof(ToString), Type.EmptyTypes);
+        public static bool IsToStringOverriden(this Type type)
+        {
+            var toStringMethod = type.GetMethod(nameof(ToString), Type.EmptyTypes);
+            return toStringMethod?.GetBaseDefinition()?.DeclaringType != toStringMethod?.DeclaringType;
+        }
 
         // Types supported by `Convert.ChangeType(...)`
         private static readonly HashSet<Type> ConvertibleTypes = new()

CliFx/Utils/NoPreambleEncoding.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Text;
+
+namespace CliFx.Utils
+{
+    // Adapted from:
+    // https://github.com/dotnet/runtime/blob/01b7e73cd378145264a7cb7a09365b41ed42b240/src/libraries/Common/src/System/Text/ConsoleEncoding.cs
+    internal class NoPreambleEncoding : Encoding
+    {
+        private readonly Encoding _underlyingEncoding;
+
+        public NoPreambleEncoding(Encoding underlyingEncoding) =>
+            _underlyingEncoding = underlyingEncoding;
+
+        public override byte[] GetPreamble() =>
+            Array.Empty<byte>();
+
+        [ExcludeFromCodeCoverage]
+        public override int GetByteCount(char[] chars, int index, int count) =>
+            _underlyingEncoding.GetByteCount(chars, index, count);
+
+        [ExcludeFromCodeCoverage]
+        public override int GetBytes(char[] chars, int charIndex, int charCount, byte[] bytes, int byteIndex) =>
+            _underlyingEncoding.GetBytes(chars, charIndex, charCount, bytes, byteIndex);
+
+        [ExcludeFromCodeCoverage]
+        public override int GetCharCount(byte[] bytes, int index, int count) =>
+            _underlyingEncoding.GetCharCount(bytes, index, count);
+
+        [ExcludeFromCodeCoverage]
+        public override int GetChars(byte[] bytes, int byteIndex, int byteCount, char[] chars, int charIndex) =>
+            _underlyingEncoding.GetChars(bytes, byteIndex, byteCount, chars, charIndex);
+
+        [ExcludeFromCodeCoverage]
+        public override int GetMaxByteCount(int charCount) =>
+            _underlyingEncoding.GetMaxByteCount(charCount);
+
+        [ExcludeFromCodeCoverage]
+        public override int GetMaxCharCount(int byteCount) =>
+            _underlyingEncoding.GetMaxCharCount(byteCount);
+    }
+
+    internal static class NoPreambleEncodingExtensions
+    {
+        public static Encoding WithoutPreamble(this Encoding encoding) =>
+            encoding.GetPreamble().Length > 0
+                ? new NoPreambleEncoding(encoding)
+                : encoding;
+    }
+}

CliFx/Utils/Polyfills.cs

@@ -24,9 +24,6 @@ internal static partial class PolyfillExtensions
         key = pair.Key;
         value = pair.Value;
     }
-
-    public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dic, TKey key) =>
-        dic.TryGetValue(key!, out var result) ? result! : default!;
 }
 
 internal static partial class PolyfillExtensions
@@ -44,4 +41,13 @@ namespace System.Linq
             new(source, comparer);
     }
 }
+
+namespace System.Collections.Generic
+{
+    internal static class PolyfillExtensions
+    {
+        public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dic, TKey key) =>
+            dic.TryGetValue(key!, out var result) ? result! : default!;
+    }
+}
 #endif

Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
 
   <PropertyGroup>
-    <Version>2.0.3</Version>
+    <Version>2.0.4</Version>
     <Company>Tyrrrz</Company>
     <Copyright>Copyright (C) Alexey Golub</Copyright>
     <LangVersion>latest</LangVersion>

NuGet.config

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <clear />
+    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+  </packageSources>
+</configuration>

Readme.md

@@ -53,7 +53,7 @@ public static class Program
 }
 ```
 
-> Note: ensure that your `Main()` method returns the integer exit code provided by `CliApplication.RunAsync()`, as shown in the above example.
+> ⚠️ Ensure that your `Main()` method returns the integer exit code provided by `CliApplication.RunAsync()`, as shown in the above example.
 Exit code is used to communicate execution result to the parent process, so it's important that your program returns it.
 
 The code above calls `AddCommandsFromThisAssembly()` to scan and resolve command types defined within the current assembly.
@@ -97,10 +97,10 @@ They can be used to show help text or application version respectively:
 
 MyApp v1.0
 
-Usage
+USAGE
   dotnet myapp.dll [options]
 
-Options
+OPTIONS
   -h|--help         Shows help text.
   --version         Shows version information.
 ```
@@ -176,13 +176,13 @@ Available parameters and options are also listed in the command's help text, whi
 
 MyApp v1.0
 
-Usage
+USAGE
   dotnet myapp.dll <value> [options]
 
-Parameters
+PARAMETERS
 * value             Value whose logarithm is to be found.
 
-Options
+OPTIONS
   -b|--base         Logarithm base. Default: "10".
   -h|--help         Shows help text.
   --version         Shows version information.
@@ -215,7 +215,7 @@ Here are some examples of how it works:
 - `myapp cmd abc -o` routes to command `cmd` (assuming it's an existing command) with parameter `abc` and sets option `'o'` without value
 
 Additionally, argument parsing in CliFx aims to be as deterministic as possible, ideally yielding the same result regardless of the application configuration.
-In fact, the only context-sensitive part in the parser is the command name resolution, which needs to know the list of available commands in order to discern between arguments that correspond to command name and arguments which map as parameters. 
+In fact, the only context-sensitive part in the parser is the command name resolution, which needs to know the list of available commands in order to discern between arguments that correspond to command name and arguments which map as parameters.
 
 The parser's context-free nature has several implications on how it consumes arguments.
 For example, passing `myapp -i file1.txt file2.txt` will always be parsed as an option with multiple values, regardless of the arity of the underlying property it's bound to.
@@ -245,61 +245,9 @@ Parameters and options can have the following underlying types:
   - Types that are assignable from arrays (`IReadOnlyList<T>`, `ICollection<T>`, etc.)
   - Types with a constructor accepting an array (`List<T>`, `HashSet<T>`, etc.)
 
-- Example command with a custom converter:
+#### Non-scalar parameters and options
 
-```csharp
-// Maps 2D vectors from AxB notation
-public class VectorConverter : BindingConverter<Vector2>
-{
-    public override Vector2 Convert(string? rawValue)
-    {
-        if (string.IsNullOrWhiteSpace(rawValue))
-            return default;
-
-        var components = rawValue.Split('x', 'X', ';');
-        var x = int.Parse(components[0], CultureInfo.InvariantCulture);
-        var y = int.Parse(components[1], CultureInfo.InvariantCulture);
-
-        return new Vector2(x, y);
-    }
-}
-
-[Command]
-public class SurfaceCalculatorCommand : ICommand
-{
-    // Custom converter is used to map raw argument values
-    [CommandParameter(0, Converter = typeof(VectorConverter))]
-    public Vector2 PointA { get; init; }
-
-    [CommandParameter(1, Converter = typeof(VectorConverter))]
-    public Vector2 PointB { get; init; }
-
-    [CommandParameter(2, Converter = typeof(VectorConverter))]
-    public Vector2 PointC { get; init; }
-
-    public ValueTask ExecuteAsync(IConsole console)
-    {
-        var a = (PointB - PointA).Length();
-        var b = (PointC - PointB).Length();
-        var c = (PointA - PointC).Length();
-
-        var p = (a + b + c) / 2;
-        var surface = Math.Sqrt(p * (p - a) * (p - b) * (p - c));
-
-        console.Output.WriteLine($"Triangle surface area: {surface}");
-
-        return default;
-    }
-}
-```
-
-```sh
-> dotnet myapp.dll 0x0 0x18 24x0
-
-Triangle surface area: 216
-```
-
-- Example command with an array-backed parameter:
+Here's an example of a command with an array-backed parameter:
 
 ```csharp
 [Command]
@@ -353,6 +301,56 @@ public class FileSizeCalculatorCommand : ICommand
 Total file size: 186368 bytes
 ```
 
+#### Custom conversion
+
+To create a custom converter for a parameter or an option, define a class that inherits from `BindingConverter<T>` and specify it in the attribute:
+
+```csharp
+// Maps 2D vectors from AxB notation
+public class VectorConverter : BindingConverter<Vector2>
+{
+    public override Vector2 Convert(string? rawValue)
+    {
+        if (string.IsNullOrWhiteSpace(rawValue))
+            return default;
+
+        var components = rawValue.Split('x', 'X', ';');
+        var x = int.Parse(components[0], CultureInfo.InvariantCulture);
+        var y = int.Parse(components[1], CultureInfo.InvariantCulture);
+
+        return new Vector2(x, y);
+    }
+}
+
+[Command]
+public class SurfaceCalculatorCommand : ICommand
+{
+    // Custom converter is used to map raw argument values
+    [CommandParameter(0, Converter = typeof(VectorConverter))]
+    public Vector2 PointA { get; init; }
+
+    [CommandParameter(1, Converter = typeof(VectorConverter))]
+    public Vector2 PointB { get; init; }
+
+    [CommandParameter(2, Converter = typeof(VectorConverter))]
+    public Vector2 PointC { get; init; }
+
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        var a = (PointB - PointA).Length();
+        var b = (PointC - PointB).Length();
+        var c = (PointA - PointC).Length();
+
+        var p = (a + b + c) / 2;
+        var surface = Math.Sqrt(p * (p - a) * (p - b) * (p - c));
+
+        console.Output.WriteLine($"Triangle surface area: {surface}");
+
+        return default;
+    }
+}
+```
+
 ### Multiple commands
 
 In order to facilitate a variety of different workflows, command line applications may provide the user with more than just a single command.
@@ -401,15 +399,15 @@ Requesting help will show direct subcommands of the current command:
 
 MyApp v1.0
 
-Usage
+USAGE
   dotnet myapp.dll [options]
   dotnet myapp.dll [command] [...]
 
-Options
+OPTIONS
   -h|--help         Shows help text.
   --version         Shows version information.
 
-Commands
+COMMANDS
   cmd1              Subcommands: cmd1 sub.
   cmd2
 
@@ -421,21 +419,21 @@ The user can also refine their help request by querying it on a specific command
 ```sh
 > dotnet myapp.dll cmd1 --help
 
-Usage
+USAGE
   dotnet myapp.dll cmd1 [options]
   dotnet myapp.dll cmd1 [command] [...]
 
-Options
+OPTIONS
   -h|--help         Shows help text.
 
-Commands
+COMMANDS
   sub
 
 You can run `dotnet myapp.dll cmd1 [command] --help` to show help on a specific command.
 ```
 
 > Note that defining a default (unnamed) command is not required.
-In the even of its absence, running the application without specifying a command will just show root level help text.
+If it's absent, running the application without specifying a command will just show root level help text.
 
 ### Reporting errors
 
@@ -479,7 +477,8 @@ Division by zero is not supported.
 133
 ```
 
-> Note that Unix systems rely on 8-bit unsigned integers to represent exit codes, which means that you can only use values between `1` and `255` to indicate an unsuccessful execution result.
+> ⚠️ Even though exit codes are represented by 32-bit integers in .NET, using values outside of 8-bit unsigned range will cause an overflow on Unix systems.
+To avoid unexpected results, use numbers between 1 and 255 for exit codes that indicate failure.
 
 ### Graceful cancellation
 
@@ -512,7 +511,7 @@ public class CancellableCommand : ICommand
 ```
 
 > Note that a command may use this approach to delay cancellation only once.
-If the user issues a second interrupt signal, the application will be immediately terminated.
+If the user issues a second interrupt signal, the application will be terminated immediately.
 
 ### Type activation
 
@@ -522,7 +521,7 @@ To facilitate that, it uses an interface called `ITypeActivator` that determines
 The default implementation of `ITypeActivator` only supports types that have public parameterless constructors, which is sufficient for majority of scenarios.
 However, in some cases you may also want to define a custom initializer, for example when integrating with an external dependency container.
 
-The following snippet shows how to configure your application to use [`Microsoft.Extensions.DependencyInjection`](https://nuget.org/packages/Microsoft.Extensions.DependencyInjection) as the type activator:
+The following example shows how to configure your application to use [`Microsoft.Extensions.DependencyInjection`](https://nuget.org/packages/Microsoft.Extensions.DependencyInjection) as the type activator in CliFx:
 
 ```csharp
 public static class Program
@@ -633,7 +632,7 @@ public async Task ConcatCommand_executes_successfully()
 ### Debug and preview mode
 
 When troubleshooting issues, you may find it useful to run your app in debug or preview mode.
-To do that, you need to pass pass the corresponding directive before any other arguments.
+To do that, you need to pass the corresponding directive before any other arguments.
 
 In order to run the application in debug mode, use the `[debug]` directive.
 This will cause the program to launch in a suspended state, waiting for debugger to be attached to the process:
@@ -697,7 +696,7 @@ public class AuthCommand : ICommand
 test
 ```
 
-Environment variables can be configured for options of non-scalar types as well.
+Environment variables can be configured for options of non-scalar types (arrays, lists, etc.) as well.
 In such case, the values of the environment variable will be split by `Path.PathSeparator` (`;` on Windows, `:` on Linux).
 
 ## Etymology