Move version option out of middleware

src/System.CommandLine.Hosting/System.CommandLine.Hosting.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <IsPackable>true</IsPackable>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
     <Description>This package provides support for using System.CommandLine with Microsoft.Extensions.Hosting.</Description>
   </PropertyGroup>
 

src/System.CommandLine.NamingConventionBinder/CommandHandler.cs

@@ -605,7 +605,7 @@ public static ICommandHandler Create<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T1
         Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, Task<int>> action) =>
         HandlerDescriptor.FromDelegate(action).GetCommandHandler();
 
-    internal static async Task<int> GetExitCodeAsync(object returnValue, InvocationContext context)
+    internal static async Task<int> GetExitCodeAsync(object? returnValue, InvocationContext context)
     {
         switch (returnValue)
         {

src/System.CommandLine.NamingConventionBinder/MethodInfoHandlerDescriptor.cs

@@ -38,7 +38,7 @@ public override ICommandHandler GetCommandHandler()
         }
     }
 
-    public override ModelDescriptor Parent => ModelDescriptor.FromType(_handlerMethodInfo.ReflectedType);
+    public override ModelDescriptor Parent => ModelDescriptor.FromType(_handlerMethodInfo.ReflectedType!);
 
     private protected override IEnumerable<ParameterDescriptor> InitializeParameterDescriptors() =>
         _handlerMethodInfo.GetParameters()

src/System.CommandLine.NamingConventionBinder/ModelBinder.cs

@@ -141,7 +141,7 @@ private bool ShortCutTheBinding()
     private (bool success, object? newInstance, bool anyNonDefaults) InstanceFromSpecificConstructor(
         BindingContext bindingContext, ConstructorDescriptor constructor, IReadOnlyList<BoundValue>? boundValues, ref bool nonDefaultsUsed)
     {
-        var values = boundValues.Select(x => x.Value).ToArray();
+        var values = boundValues?.Select(x => x.Value).ToArray() ?? Array.Empty<object>();
         object? newInstance = null;
         try
         {
@@ -332,7 +332,7 @@ private static BoundValue DefaultForValueDescriptor(
             valueSource);
     }
 
-    private protected IValueDescriptor FindModelPropertyDescriptor(Type propertyType, string propertyName)
+    private protected IValueDescriptor? FindModelPropertyDescriptor(Type propertyType, string propertyName)
     {
         return ModelDescriptor.PropertyDescriptors
                               .FirstOrDefault(desc =>

src/System.CommandLine.NamingConventionBinder/ModelBinder{T}.cs

@@ -25,10 +25,12 @@ public void BindMemberFromValue<TValue>(
         IValueDescriptor valueDescriptor)
     {
         var (propertyType, propertyName) = property.MemberTypeAndName();
-        var propertyDescriptor = FindModelPropertyDescriptor(
-            propertyType, propertyName);
-        MemberBindingSources[propertyDescriptor] = 
-            new SpecificSymbolValueSource(valueDescriptor);
+        var propertyDescriptor = FindModelPropertyDescriptor(propertyType, propertyName);
+
+        if (propertyDescriptor is not null)
+        {
+            MemberBindingSources[propertyDescriptor] = new SpecificSymbolValueSource(valueDescriptor);
+        }
     }
 
     /// <summary>
@@ -42,9 +44,10 @@ public void BindMemberFromValue<TValue>(
         Func<BindingContext?, TValue> getValue)
     {
         var (propertyType, propertyName) = property.MemberTypeAndName();
-        var propertyDescriptor = FindModelPropertyDescriptor(
-            propertyType, propertyName);
-        MemberBindingSources[propertyDescriptor] =
-            new DelegateValueSource(c => getValue(c));
+        var propertyDescriptor = FindModelPropertyDescriptor(propertyType, propertyName);
+        if (propertyDescriptor is not null)
+        {
+            MemberBindingSources[propertyDescriptor] = new DelegateValueSource(c => getValue(c));
+        }
     }
 }

src/System.CommandLine.NamingConventionBinder/ModelBindingCommandHandler.cs

@@ -31,7 +31,7 @@ internal ModelBindingCommandHandler(
         _handlerMethodInfo = handlerMethodInfo ?? throw new ArgumentNullException(nameof(handlerMethodInfo));
         _invocationTargetBinder = _handlerMethodInfo.IsStatic
                                       ? null
-                                      : new ModelBinder(_handlerMethodInfo.ReflectedType);
+                                      : new ModelBinder(_handlerMethodInfo.ReflectedType!);
         _methodDescriptor = methodDescriptor ?? throw new ArgumentNullException(nameof(methodDescriptor));
         _invocationTarget = invocationTarget;
     }
@@ -69,11 +69,11 @@ public async Task<int> InvokeAsync(InvocationContext context)
                                   .Select(x => x.Value)
                                   .ToArray();
 
-        object result;
+        object? result;
         if (_handlerDelegate is null)
         {
             var invocationTarget = _invocationTarget ?? 
-                                   bindingContext.GetService(_handlerMethodInfo!.ReflectedType);
+                                   bindingContext.GetService(_handlerMethodInfo!.ReflectedType!);
             if(invocationTarget is { })
             {
                 _invocationTargetBinder?.UpdateInstance(invocationTarget, bindingContext);

src/System.CommandLine.NamingConventionBinder/ModelDescriptor.cs

@@ -46,7 +46,7 @@ protected ModelDescriptor(Type modelType)
     public IReadOnlyList<IValueDescriptor> PropertyDescriptors =>
         _propertyDescriptors ??=
             ModelType.GetProperties(CommonBindingFlags)
-                     .Where(p => p.CanWrite && p.SetMethod.IsPublic)
+                     .Where(p => p.CanWrite && p.SetMethod?.IsPublic == true)
                      .Select(i => new PropertyDescriptor(i, this))
                      .ToList();
 

src/System.CommandLine.NamingConventionBinder/ParameterDescriptor.cs

@@ -23,7 +23,7 @@ internal ParameterDescriptor(
     }
 
     /// <inheritdoc />
-    public string ValueName => _parameterInfo.Name;
+    public string ValueName => _parameterInfo.Name!;
 
     /// <summary>
     /// The method descriptor that this constructor belongs to.

src/System.CommandLine.NamingConventionBinder/System.CommandLine.NamingConventionBinder.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <IsPackable>true</IsPackable>
     <PackageId>System.CommandLine.NamingConventionBinder</PackageId>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>net7.0;netstandard2.0</TargetFrameworks>
     <LangVersion>10</LangVersion>
     <Nullable>enable</Nullable>
     <Description>This package provides command handler support for System.CommandLine performs parameter and model binding by matching option and argument names to parameter and property names.</Description>

src/System.CommandLine.Tests/VersionOptionTests.cs

@@ -73,7 +73,7 @@ public async Task When_the_version_option_is_specified_and_there_are_default_opt
         {
             var rootCommand = new RootCommand
             {
-                new Option<bool>("-x")
+                new Option<bool>("-x", defaultValueFactory: () => true)
             };
             rootCommand.SetHandler(() => { });
 
@@ -126,21 +126,9 @@ public void Version_is_not_valid_with_other_tokens(string commandLine)
                 .UseVersionOption()
                 .Build();
 
-            var console = new TestConsole();
-
-            var result = parser.Invoke(commandLine, console);
+            var result = parser.Parse(commandLine);
 
-            console.Out
-                   .ToString()
-                   .Should()
-                   .NotContain(version);
-
-            console.Error
-                   .ToString()
-                   .Should()
-                   .Contain("--version option cannot be combined with other arguments.");
-
-            result.Should().NotBe(0);
+            result.Errors.Should().Contain(e => e.Message == "--version option cannot be combined with other arguments.");
         }
 
         [Fact]
@@ -206,7 +194,7 @@ public async Task Version_can_specify_additional_alias()
         [Fact]
         public void Version_is_not_valid_with_other_tokens_uses_custom_alias()
         {
-            var childCommand =  new Command("subcommand");
+            var childCommand = new Command("subcommand");
             childCommand.SetHandler(() => { });
             var rootCommand = new RootCommand
             {
@@ -215,24 +203,12 @@ public void Version_is_not_valid_with_other_tokens_uses_custom_alias()
             rootCommand.SetHandler(() => { });
 
             var parser = new CommandLineBuilder(rootCommand)
-                .UseVersionOption("-v")
-                .Build();
-
-            var console = new TestConsole();
-
-            var result = parser.Invoke("-v subcommand", console);
-
-            console.Out
-                   .ToString()
-                   .Should()
-                   .NotContain(version);
+                         .UseVersionOption("-v")
+                         .Build();
 
-            console.Error
-                   .ToString()
-                   .Should()
-                   .Contain("-v option cannot be combined with other arguments.");
+            var result = parser.Parse("-v subcommand");
 
-            result.Should().NotBe(0);
+            result.Errors.Should().ContainSingle(e => e.Message == "-v option cannot be combined with other arguments.");
         }
     }
 }

src/System.CommandLine/Builder/CommandLineBuilderExtensions.cs

@@ -9,7 +9,6 @@
 using System.CommandLine.Parsing;
 using System.IO;
 using System.Linq;
-using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
 using static System.Environment;
@@ -22,24 +21,6 @@ namespace System.CommandLine
     /// </summary>
     public static class CommandLineBuilderExtensions
     {
-        private static readonly Lazy<string> _assemblyVersion =
-            new(() =>
-            {
-                var assembly = RootCommand.GetAssembly();
-
-                var assemblyVersionAttribute = assembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>();
-
-                if (assemblyVersionAttribute is null)
-                {
-                    return assembly.GetName().Version?.ToString() ?? "";
-                }
-                else
-                {
-                    return assemblyVersionAttribute.InformationalVersion;
-                }
-
-            });
-
         /// <summary>
         /// Enables signaling and handling of process termination via a <see cref="CancellationToken"/> that can be passed to a <see cref="ICommandHandler"/> during invocation.
         /// </summary>
@@ -643,25 +624,6 @@ public static CommandLineBuilder UseVersionOption(
             builder.VersionOption = versionOption;
             builder.Command.Options.Add(versionOption);
 
-            builder.AddMiddleware(async (context, next) =>
-            {
-                if (context.ParseResult.FindResultFor(versionOption) is { })
-                {
-                    if (context.ParseResult.Errors.Any(e => e.SymbolResult is OptionResult optionResult && optionResult.Option is VersionOption))
-                    {
-                        context.InvocationResult = static ctx => ParseErrorResult.Apply(ctx, null);
-                    }
-                    else
-                    {
-                        context.Console.Out.WriteLine(_assemblyVersion.Value);
-                    }
-                }
-                else
-                {
-                    await next(context);
-                }
-            }, MiddlewareOrderInternal.VersionOption);
-
             return builder;
         }
 
@@ -684,25 +646,6 @@ public static CommandLineBuilder UseVersionOption(
             builder.VersionOption = versionOption;
             command.Options.Add(versionOption);
 
-            builder.AddMiddleware(async (context, next) =>
-            {
-                if (context.ParseResult.FindResultFor(versionOption) is { })
-                {
-                    if (context.ParseResult.Errors.Any(e => e.SymbolResult is OptionResult optionResult && optionResult.Option is VersionOption))
-                    {
-                        context.InvocationResult = static ctx => ParseErrorResult.Apply(ctx, null);
-                    }
-                    else
-                    {
-                        context.Console.Out.WriteLine(_assemblyVersion.Value);
-                    }
-                }
-                else
-                {
-                    await next(context);
-                }
-            }, MiddlewareOrderInternal.VersionOption);
-
             return builder;
         }
 

src/System.CommandLine/Help/HelpOption.cs

@@ -12,7 +12,6 @@ public HelpOption(string[] aliases, Func<LocalizationResources> getLocalizationR
             : base(aliases, null, new Argument<bool> { Arity = ArgumentArity.Zero })
         {
             _localizationResources = getLocalizationResources;
-            DisallowBinding = true;
         }
 
         public HelpOption(Func<LocalizationResources> getLocalizationResources) : this(new[]

src/System.CommandLine/Help/VersionOption.cs

@@ -15,17 +15,13 @@ internal class VersionOption : Option<bool>
         {
             _builder = builder;
 
-            DisallowBinding = true;
-
             AddValidators();
         }
 
         public VersionOption(string[] aliases, CommandLineBuilder builder) : base(aliases)
         {
             _builder = builder;
 
-            DisallowBinding = true;
-
             AddValidators();
         }
 

src/System.CommandLine/Invocation/InvocationPipeline.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System.Collections.Generic;
+using System.CommandLine.Parsing;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -21,15 +22,15 @@ public Task<int> InvokeAsync(IConsole? console = null, CancellationToken cancell
         {
             var context = new InvocationContext(_parseResult, console, cancellationToken);
 
-            if (context.Parser.Configuration.Middleware.Count == 0
-                && context.ParseResult.CommandResult.Command.Handler is ICommandHandler handler)
+            if (context.Parser.Configuration.Middleware.Count == 0 && 
+                _parseResult.Handler is not null)
             {
-                return handler.InvokeAsync(context);
+                return _parseResult.Handler.InvokeAsync(context);
             }
 
-            return FullInvocationChainAsync(context);
+            return InvokeHandlerWithMiddleware(context);
 
-            static async Task<int> FullInvocationChainAsync(InvocationContext context)
+            static async Task<int> InvokeHandlerWithMiddleware(InvocationContext context)
             {
                 InvocationMiddleware invocationChain = BuildInvocationChain(context, true);
 
@@ -49,9 +50,9 @@ public int Invoke(IConsole? console = null)
                 return handler.Invoke(context);
             }
 
-            return FullInvocationChain(context); // kept in a separate method to avoid JITting
+            return InvokeHandlerWithMiddleware(context); // kept in a separate method to avoid JITting
 
-            static int FullInvocationChain(InvocationContext context)
+            static int InvokeHandlerWithMiddleware(InvocationContext context)
             {
                 InvocationMiddleware invocationChain = BuildInvocationChain(context, false);
 
@@ -68,27 +69,19 @@ private static InvocationMiddleware BuildInvocationChain(InvocationContext conte
 
             invocations.Add(async (invocationContext, _) =>
             {
-                if (invocationContext
-                    .ParseResult
-                    .CommandResult
-                    .Command is Command command)
+                if (invocationContext.ParseResult.Handler is { } handler)
                 {
-                    var handler = command.Handler;
-
-                    if (handler is not null)
-                    {
-                        context.ExitCode = invokeAsync
-                            ? await handler.InvokeAsync(invocationContext)
-                            : handler.Invoke(invocationContext);
-                    }
+                    context.ExitCode = invokeAsync
+                                           ? await handler.InvokeAsync(invocationContext)
+                                           : handler.Invoke(invocationContext);
                 }
             });
 
             return invocations.Aggregate(
                 (first, second) =>
                     (ctx, next) =>
                         first(ctx,
-                            c => second(c, next)));
+                              c => second(c, next)));
         }
 
         private static int GetExitCode(InvocationContext context)

src/System.CommandLine/Option.cs

@@ -77,8 +77,6 @@ public ArgumentArity Arity
         /// </summary>
         internal bool IsGlobal { get; set; }
 
-        internal bool DisallowBinding { get; init; }
-
         /// <summary>
         /// Validators that will be called when the option is matched by the parser.
         /// </summary>