Introduce CliAction, make it possible for every Symbol to define one

samples/HostingPlayground/Program.cs

@@ -32,7 +32,7 @@ private static CommandLineBuilder BuildCommandLine()
                     IsRequired = true
                 }
             };
-            root.Handler = CommandHandler.Create<GreeterOptions, IHost>(Run);
+            root.Action = CommandHandler.Create<GreeterOptions, IHost>(Run);
             return new CommandLineBuilder(root);
         }
 

src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_NamingConventionBinder_api_is_not_changed.approved.txt

@@ -17,10 +17,8 @@ System.CommandLine.NamingConventionBinder
     public static System.Void AddModelBinder(this System.CommandLine.Binding.BindingContext bindingContext, ModelBinder binder)
     public static System.CommandLine.Binding.BindingContext GetBindingContext(this System.CommandLine.Invocation.InvocationContext ctx)
     public static ModelBinder GetOrCreateModelBinder(this System.CommandLine.Binding.BindingContext bindingContext, System.CommandLine.Binding.IValueDescriptor valueDescriptor)
-  public abstract class BindingHandler, System.CommandLine.ICommandHandler
+  public abstract class BindingHandler : System.CommandLine.CliAction
     public System.CommandLine.Binding.BindingContext GetBindingContext(System.CommandLine.Invocation.InvocationContext invocationContext)
-    public System.Int32 Invoke(System.CommandLine.Invocation.InvocationContext context)
-    public System.Threading.Tasks.Task<System.Int32> InvokeAsync(System.CommandLine.Invocation.InvocationContext context, System.Threading.CancellationToken cancellationToken = null)
     public System.CommandLine.Binding.BindingContext SetBindingContext(System.CommandLine.Binding.BindingContext bindingContext)
   public static class CommandHandler
     public static BindingHandler Create(System.Delegate delegate)
@@ -115,7 +113,7 @@ System.CommandLine.NamingConventionBinder
     .ctor()
     public System.Void BindMemberFromValue<TValue>(Expression<Func<TModel,TValue>> property, System.CommandLine.Binding.IValueDescriptor valueDescriptor)
     public System.Void BindMemberFromValue<TValue>(Expression<Func<TModel,TValue>> property, Func<System.CommandLine.Binding.BindingContext,TValue> getValue)
-  public class ModelBindingCommandHandler : BindingHandler, System.CommandLine.ICommandHandler
+  public class ModelBindingCommandHandler : BindingHandler
     public System.Void BindParameter(System.Reflection.ParameterInfo param, System.CommandLine.Argument argument)
     public System.Void BindParameter(System.Reflection.ParameterInfo param, System.CommandLine.Option option)
     public System.Int32 Invoke(System.CommandLine.Invocation.InvocationContext context)

src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt

@@ -35,12 +35,15 @@ System.CommandLine
     public static Argument<System.IO.DirectoryInfo> AcceptExistingOnly(this Argument<System.IO.DirectoryInfo> argument)
     public static Argument<System.IO.FileSystemInfo> AcceptExistingOnly(this Argument<System.IO.FileSystemInfo> argument)
     public static Argument<T> AcceptExistingOnly<T>(this Argument<T> argument)
+  public abstract class CliAction
+    public System.Int32 Invoke(System.CommandLine.Invocation.InvocationContext context)
+    public System.Threading.Tasks.Task<System.Int32> InvokeAsync(System.CommandLine.Invocation.InvocationContext context, System.Threading.CancellationToken cancellationToken = null)
   public class Command : Symbol, System.Collections.Generic.IEnumerable<Symbol>, System.Collections.IEnumerable
     .ctor(System.String name, System.String description = null)
+    public CliAction Action { get; set; }
     public System.Collections.Generic.ICollection<System.String> Aliases { get; }
     public System.Collections.Generic.IList<Argument> Arguments { get; }
     public System.Collections.Generic.IEnumerable<Symbol> Children { get; }
-    public ICommandHandler Handler { get; set; }
     public System.Collections.Generic.IList<Option> Options { get; }
     public System.Collections.Generic.IList<Command> Subcommands { get; }
     public System.Boolean TreatUnmatchedTokensAsErrors { get; set; }
@@ -50,8 +53,8 @@ System.CommandLine
     public System.Collections.Generic.IEnumerator<Symbol> GetEnumerator()
     public ParseResult Parse(System.Collections.Generic.IReadOnlyList<System.String> args, CommandLineConfiguration configuration = null)
     public ParseResult Parse(System.String commandLine, CommandLineConfiguration configuration = null)
-    public System.Void SetHandler(System.Func<System.CommandLine.Invocation.InvocationContext,System.Int32> handler)
-    public System.Void SetHandler(System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.CancellationToken,System.Threading.Tasks.Task<System.Int32>> handler)
+    public System.Void SetAction(System.Action<System.CommandLine.Invocation.InvocationContext> action)
+    public System.Void SetAction(System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.CancellationToken,System.Threading.Tasks.Task> action)
   public static class CommandExtensions
     public static System.Int32 Invoke(this Command command, System.String[] args, IConsole console = null)
     public static System.Int32 Invoke(this Command command, System.String commandLine, IConsole console = null)
@@ -104,17 +107,14 @@ System.CommandLine
     public static System.Void Write(this IConsole console, System.String value)
     public static System.Void WriteLine(this IConsole console, System.String value)
   public class Directive : Symbol
-    .ctor(System.String name, System.Func<System.CommandLine.Invocation.InvocationContext,System.Int32> syncHandler = null, System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.CancellationToken,System.Threading.Tasks.Task<System.Int32>> asyncHandler = null)
+    .ctor(System.String name)
+    public CliAction Action { get; set; }
     public System.Collections.Generic.IEnumerable<System.CommandLine.Completions.CompletionItem> GetCompletions(System.CommandLine.Completions.CompletionContext context)
-    public System.Void SetAsynchronousHandler(System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.CancellationToken,System.Threading.Tasks.Task<System.Int32>> handler)
-    public System.Void SetSynchronousHandler(System.Func<System.CommandLine.Invocation.InvocationContext,System.Int32> handler)
   public class EnvironmentVariablesDirective : Directive
     .ctor()
-  public interface ICommandHandler
-    public System.Int32 Invoke(System.CommandLine.Invocation.InvocationContext context)
-    public System.Threading.Tasks.Task<System.Int32> InvokeAsync(System.CommandLine.Invocation.InvocationContext context, System.Threading.CancellationToken cancellationToken = null)
   public interface IConsole : System.CommandLine.IO.IStandardError, System.CommandLine.IO.IStandardIn, System.CommandLine.IO.IStandardOut
   public abstract class Option : Symbol, System.CommandLine.Binding.IValueDescriptor
+    public CliAction Action { get; set; }
     public System.Collections.Generic.ICollection<System.String> Aliases { get; }
     public System.Boolean AllowMultipleArgumentsPerToken { get; set; }
     public System.Boolean AppliesToSelfAndChildren { get; set; }
@@ -140,6 +140,7 @@ System.CommandLine
   public class ParseDirective : Directive
     .ctor(System.Int32 errorExitCode = 1)
   public class ParseResult
+    public CliAction Action { get; }
     public System.CommandLine.Parsing.CommandResult CommandResult { get; }
     public CommandLineConfiguration Configuration { get; }
     public System.Collections.Generic.IReadOnlyList<System.CommandLine.Parsing.ParseError> Errors { get; }

src/System.CommandLine.Benchmarks/CommandLine/Perf_Parser_Simple.cs

@@ -33,12 +33,10 @@ private static RootCommand BuildCommand()
                 stringOption
             };
 
-            command.SetHandler(ctx => 
+            command.SetAction(ctx => 
             {
                 bool boolean = ctx.ParseResult.GetValue(boolOption);
                 string text = ctx.ParseResult.GetValue(stringOption);
-
-                return 0;
             });
 
             return command;

src/System.CommandLine.DragonFruit/CommandLine.cs

@@ -168,7 +168,7 @@ public static void ConfigureFromMethod(
                 command.Arguments.Add(ArgumentBuilder.CreateArgument(argsParam));
             }
 
-            command.Handler = CommandHandler.Create(method, target);
+            command.Action = CommandHandler.Create(method, target);
         }
 
         public static CommandLineBuilder ConfigureHelpFromXmlComments(

src/System.CommandLine.Generator/CommandHandlerSourceGenerator.cs

@@ -11,7 +11,7 @@ namespace System.CommandLine.Generator
     [Generator]
     public class CommandHandlerSourceGenerator : ISourceGenerator
     {
-        private const string ICommandHandlerType = "System.CommandLine.ICommandHandler";
+        private const string CliActionType = "System.CommandLine.CliAction";
 
         public void Execute(GeneratorExecutionContext context)
         {
@@ -74,7 +74,7 @@ private static void GenerateHandlerClass(
             int handlerCount)
         {
             builder.Append($@"
-        private class GeneratedHandler_{handlerCount} : {ICommandHandlerType}
+        private class GeneratedHandler_{handlerCount} : {CliActionType}
         {{
             public GeneratedHandler_{handlerCount}(
                 {invocation.DelegateType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)} method");
@@ -115,10 +115,10 @@ private class GeneratedHandler_{handlerCount} : {ICommandHandlerType}
             }
 
             builder.Append($@"
-            public int Invoke(global::System.CommandLine.Invocation.InvocationContext context) => InvokeAsync(context, global::System.Threading.CancellationToken.None).GetAwaiter().GetResult();");
+            public override int Invoke(global::System.CommandLine.Invocation.InvocationContext context) => InvokeAsync(context, global::System.Threading.CancellationToken.None).GetAwaiter().GetResult();");
 
             builder.Append($@"
-            public async global::System.Threading.Tasks.Task<int> InvokeAsync(global::System.CommandLine.Invocation.InvocationContext context, global::System.Threading.CancellationToken cancellationToken)
+            public override async global::System.Threading.Tasks.Task<int> InvokeAsync(global::System.CommandLine.Invocation.InvocationContext context, global::System.Threading.CancellationToken cancellationToken)
             {{");
             builder.Append($@"
                 {invocation.InvokeContents()}");
@@ -170,7 +170,7 @@ private static void GenerateSetHandler(
             builder.Append(@"
         {");
             builder.Append($@"
-            command.Handler = new GeneratedHandler_{handlerCount}(method");
+            command.Action = new GeneratedHandler_{handlerCount}(method");
 
             if (methodParameters.Length > 0)
             {

src/System.CommandLine.Hosting.Tests/HostingHandlerTest.cs

@@ -134,17 +134,17 @@ public static async Task Invokes_DerivedClass()
             service.StringValue.Should().Be("TEST");
         }
 
-        public abstract class MyBaseHandler : ICommandHandler
+        public abstract class MyBaseHandler : CliAction
         {
             public int IntOption { get; set; } // bound from option
             public IConsole Console { get; set; } // bound from DI
 
-            public int Invoke(InvocationContext context)
+            public override int Invoke(InvocationContext context)
             {
                 return Act();
             }
 
-            public Task<int> InvokeAsync(InvocationContext context, CancellationToken cancellationToken)
+            public override Task<int> InvokeAsync(InvocationContext context, CancellationToken cancellationToken)
             {
                 return Task.FromResult(Act());
             }
@@ -159,7 +159,7 @@ public MyCommand() : base(name: "mycommand")
                 Options.Add(new Option<int>("--int-option")); // or nameof(Handler.IntOption).ToKebabCase() if you don't like the string literal
             }
 
-            public class MyHandler : ICommandHandler
+            public class MyHandler : CliAction
             {
                 private readonly MyService service;
 
@@ -171,13 +171,13 @@ public MyHandler(MyService service)
                 public int IntOption { get; set; } // bound from option
                 public IConsole Console { get; set; } // bound from DI
 
-                public int Invoke(InvocationContext context)
+                public override int Invoke(InvocationContext context)
                 {
                     service.Value = IntOption;
                     return IntOption;
                 }
 
-                public Task<int> InvokeAsync(InvocationContext context, CancellationToken cancellationToken)
+                public override Task<int> InvokeAsync(InvocationContext context, CancellationToken cancellationToken)
                 {
                     service.Value = IntOption;
                     return Task.FromResult(IntOption);
@@ -209,7 +209,7 @@ public MyOtherCommand() : base(name: "myothercommand")
                 Arguments.Add(new Argument<string>("One") {  Arity = ArgumentArity.ZeroOrOne });
             }
 
-            public class MyHandler : ICommandHandler
+            public class MyHandler : CliAction
             {
                 private readonly MyService service;
 
@@ -223,9 +223,9 @@ public MyHandler(MyService service)
 
                 public string One { get; set; }
 
-                public int Invoke(InvocationContext context) => InvokeAsync(context, CancellationToken.None).GetAwaiter().GetResult();
+                public override int Invoke(InvocationContext context) => InvokeAsync(context, CancellationToken.None).GetAwaiter().GetResult();
 
-                public Task<int> InvokeAsync(InvocationContext context, CancellationToken cancellationToken)
+                public override Task<int> InvokeAsync(InvocationContext context, CancellationToken cancellationToken)
                 {
                     service.Value = IntOption;
                     service.StringValue = One;

src/System.CommandLine.Hosting.Tests/HostingTests.cs

@@ -28,7 +28,7 @@ void Execute(IHost host)
             }
 
             var config = new CommandLineBuilder(
-                new RootCommand { Handler = CommandHandler.Create<IHost>(Execute) }
+                new RootCommand { Action = CommandHandler.Create<IHost>(Execute) }
                 )
                 .UseHost()
                 .Build();
@@ -76,7 +76,7 @@ void Execute(IHost host)
             }
 
             var config = new CommandLineBuilder(
-                new RootCommand { Handler = CommandHandler.Create<IHost>(Execute) }
+                new RootCommand { Action = CommandHandler.Create<IHost>(Execute) }
                 )
                 .UseHost()
                 .Build();
@@ -108,7 +108,7 @@ void Execute(IHost host)
             var config = new CommandLineBuilder(
                 new RootCommand
                 {
-                    Handler = CommandHandler.Create<IHost>(Execute),
+                    Action = CommandHandler.Create<IHost>(Execute),
                 })
                 .UseHost(host =>
                 {
@@ -145,7 +145,7 @@ void Execute(IHost host)
             var config = new CommandLineBuilder(
                 new RootCommand
                 {
-                    Handler = CommandHandler.Create<IHost>(Execute),
+                    Action = CommandHandler.Create<IHost>(Execute),
                 })
                 .UseHost(args =>
                 {
@@ -184,7 +184,7 @@ void Execute(IHost host)
             var config = new CommandLineBuilder(
                 new RootCommand
                 {
-                    Handler = CommandHandler.Create<IHost>(Execute)
+                    Action = CommandHandler.Create<IHost>(Execute)
                 })
                 .UseHost()
                 .Build();
@@ -203,7 +203,7 @@ public static void UseHost_binds_parsed_arguments_to_options()
 
             var rootCmd = new RootCommand();
             rootCmd.Options.Add(new Option<int>($"-{nameof(MyOptions.MyArgument)}"));
-            rootCmd.Handler = CommandHandler.Create((IHost host) =>
+            rootCmd.Action = CommandHandler.Create((IHost host) =>
             {
                 options = host.Services
                     .GetRequiredService<IOptions<MyOptions>>()

src/System.CommandLine.Hosting/HostingExtensions.cs

@@ -88,7 +88,7 @@ public static OptionsBuilder<TOptions> BindCommandLine<TOptions>(
 
         public static IHostBuilder UseCommandHandler<TCommand, THandler>(this IHostBuilder builder)
             where TCommand : Command
-            where THandler : ICommandHandler
+            where THandler : CliAction
         {
             return builder.UseCommandHandler(typeof(TCommand), typeof(THandler));
         }
@@ -100,9 +100,9 @@ public static IHostBuilder UseCommandHandler(this IHostBuilder builder, Type com
                 throw new ArgumentException($"{nameof(commandType)} must be a type of {nameof(Command)}", nameof(handlerType));
             }
 
-            if (!typeof(ICommandHandler).IsAssignableFrom(handlerType))
+            if (!typeof(CliAction).IsAssignableFrom(handlerType))
             {
-                throw new ArgumentException($"{nameof(handlerType)} must implement {nameof(ICommandHandler)}", nameof(handlerType));
+                throw new ArgumentException($"{nameof(handlerType)} must implement {nameof(CliAction)}", nameof(handlerType));
             }
 
             if (builder.Properties[typeof(InvocationContext)] is InvocationContext invocation 
@@ -114,10 +114,10 @@ public static IHostBuilder UseCommandHandler(this IHostBuilder builder, Type com
                     services.AddTransient(handlerType);
                 });
 
-                BindingHandler bindingHandler = CommandHandler.Create(handlerType.GetMethod(nameof(ICommandHandler.InvokeAsync)));
+                BindingHandler bindingHandler = CommandHandler.Create(handlerType.GetMethod(nameof(CliAction.InvokeAsync)));
                 // NullBindingHandler that accumulated services registered so far, before handler creation
-                bindingHandler.SetBindingContext(command.Handler is BindingHandler pre ? pre.GetBindingContext(invocation) : null);
-                command.Handler = bindingHandler;
+                bindingHandler.SetBindingContext(command.Action is BindingHandler pre ? pre.GetBindingContext(invocation) : null);
+                command.Action = bindingHandler;
                 bindingHandler.GetBindingContext(invocation).AddService(handlerType, c => c.GetService<IHost>().Services.GetService(handlerType));
             }