The handler should always return an integer

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

@@ -50,8 +50,8 @@ 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.Action<System.CommandLine.Invocation.InvocationContext> handle)
-    public System.Void SetHandler(System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.CancellationToken,System.Threading.Tasks.Task> handle)
+    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 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)
@@ -69,7 +69,7 @@ System.CommandLine
     public CommandLineBuilder RegisterWithDotnetSuggest()
     public CommandLineBuilder UseDefaults()
     public CommandLineBuilder UseEnvironmentVariableDirective()
-    public CommandLineBuilder UseExceptionHandler(System.Action<System.Exception,System.CommandLine.Invocation.InvocationContext> onException = null, System.Nullable<System.Int32> errorExitCode = null)
+    public CommandLineBuilder UseExceptionHandler(System.Func<System.Exception,System.CommandLine.Invocation.InvocationContext,System.Int32> onException = null, System.Int32 errorExitCode = 1)
     public CommandLineBuilder UseHelp(System.Nullable<System.Int32> maxWidth = null)
     public CommandLineBuilder UseHelp(System.String name, System.String[] helpAliases)
     public CommandLineBuilder UseHelp(System.Action<System.CommandLine.Help.HelpContext> customize, System.Nullable<System.Int32> maxWidth = null)
@@ -104,10 +104,10 @@ 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.Action<System.CommandLine.Invocation.InvocationContext> syncHandler = null, System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.CancellationToken,System.Threading.Tasks.Task> asyncHandler = null)
+    .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)
     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> handler)
-    public System.Void SetSynchronousHandler(System.Action<System.CommandLine.Invocation.InvocationContext> handler)
+    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
@@ -255,9 +255,7 @@ System.CommandLine.Invocation
     .ctor(System.CommandLine.ParseResult parseResult, System.CommandLine.IConsole console = null)
     public System.CommandLine.Binding.BindingContext BindingContext { get; }
     public System.CommandLine.IConsole Console { get; set; }
-    public System.Int32 ExitCode { get; set; }
     public System.CommandLine.Help.HelpBuilder HelpBuilder { get; }
-    public System.Action<InvocationContext> InvocationResult { get; set; }
     public System.CommandLine.ParseResult ParseResult { get; set; }
     public T GetValue<T>(Option<T> option)
     public T GetValue<T>(Argument<T> argument)

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

@@ -37,6 +37,8 @@ private static RootCommand BuildCommand()
             {
                 bool boolean = ctx.ParseResult.GetValue(boolOption);
                 string text = ctx.ParseResult.GetValue(stringOption);
+
+                return 0;
             });
 
             return command;

src/System.CommandLine.Generator/Invocations/ConstructorModelBindingInvocation.cs

@@ -48,17 +48,17 @@ public override string InvokeContents()
             {
                 case ReturnPattern.InvocationContextExitCode:
                     builder.Append(@"
-                return await global::System.Threading.Tasks.Task.FromResult(context.ExitCode);");
+                return 0;");
                     break;
                 case ReturnPattern.FunctionReturnValue:
                     builder.Append(@"
-                return await global::System.Threading.Tasks.Task.FromResult(rv);");
+                return rv;");
                     break;
                 case ReturnPattern.AwaitFunction:
                     builder.Append(@"
                 await rv;");
                     builder.Append(@"
-                return context.ExitCode;");
+                return 0;");
                     break;
                 case ReturnPattern.AwaitFunctionReturnValue:
                     builder.Append(@"

src/System.CommandLine.Generator/Invocations/DelegateInvocation.cs

@@ -50,17 +50,17 @@ public virtual string InvokeContents()
             {
                 case ReturnPattern.InvocationContextExitCode:
                     builder.Append(@"
-                return await Task.FromResult(context.ExitCode);");
+                return 0;");
                     break;
                 case ReturnPattern.FunctionReturnValue:
                     builder.Append(@"
-                return await Task.FromResult(rv);");
+                return rv;");
                     break;
                 case ReturnPattern.AwaitFunction:
                     builder.Append(@"
                 await rv;");
                     builder.Append(@"
-                return context.ExitCode;");
+                return 0;");
                     break;
                 case ReturnPattern.AwaitFunctionReturnValue:
                     builder.Append(@"

src/System.CommandLine.Hosting/HostingExtensions.cs

@@ -36,7 +36,6 @@ public static CommandLineBuilder UseHost(this CommandLineBuilder builder,
                     services.AddSingleton(invocation);
                     services.AddSingleton(invocation.BindingContext);
                     services.AddSingleton(invocation.Console);
-                    services.AddTransient(_ => invocation.InvocationResult);
                     services.AddTransient(_ => invocation.ParseResult);
                 });
                 hostBuilder.UseInvocationLifetime(invocation);

src/System.CommandLine.NamingConventionBinder.Tests/ModelBindingCommandHandlerTests.cs

@@ -321,16 +321,12 @@ public async Task Unexpected_return_types_result_in_exit_code_0_if_no_exception_
     private static void CaptureMethod<T>(T value, InvocationContext invocationContext)
     {
         BoundValueCapturer.Capture(value, invocationContext);
-
-        invocationContext.InvocationResult = ctx => BoundValueCapturer.Apply(ctx);
     }
 
     private static Action<T, InvocationContext> CaptureDelegate<T>()
         => (value, invocationContext) =>
         {
             BoundValueCapturer.Capture(value, invocationContext);
-
-            invocationContext.InvocationResult = ctx => BoundValueCapturer.Apply(ctx);
         };
 
     private static class BoundValueCapturer

src/System.CommandLine.NamingConventionBinder/CommandHandler.cs

@@ -611,13 +611,10 @@ internal static async Task<int> GetExitCodeAsync(object? returnValue, Invocation
         {
             case Task<int> exitCodeTask:
                 return await exitCodeTask;
-            case Task task:
-                await task;
-                return context.ExitCode;
             case int exitCode:
                 return exitCode;
             default:
-                return context.ExitCode;
+                return 0;
         }
     }
 }

src/System.CommandLine.Suggest.Tests/EndToEndTestApp/Program.cs

@@ -30,7 +30,7 @@ static async Task Main(string[] args)
                 string cherry = ctx.ParseResult.GetValue(cherryOption);
                 string durian = ctx.ParseResult.GetValue(durianOption);
 
-                return Task.CompletedTask;
+                return Task.FromResult(0);
             });
 
             var commandLine = new CommandLineBuilder(rootCommand)

src/System.CommandLine.Suggest/SuggestionDispatcher.cs

@@ -7,6 +7,7 @@
 using System.CommandLine.Parsing;
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace System.CommandLine.Suggest
@@ -31,6 +32,7 @@ public SuggestionDispatcher(ISuggestionRegistration suggestionRegistration, ISug
             CompleteScriptCommand.SetHandler(context =>
             {
                 SuggestionShellScriptHandler.Handle(context.Console, context.ParseResult.GetValue(shellTypeArgument));
+                return 0;
             });
 
             ListCommand = new Command("list")
@@ -48,7 +50,7 @@ public SuggestionDispatcher(ISuggestionRegistration suggestionRegistration, ISug
                 ExecutableOption,
                 PositionOption
             };
-            GetCommand.SetHandler(context => Get(context));
+            GetCommand.SetHandler(Get);
 
             var commandPathOption = new Option<string>("--command-path") { Description = "The path to the command for which to register suggestions" };
 
@@ -132,7 +134,7 @@ private void Register(
             }
         }
 
-        private Task<int> Get(InvocationContext context)
+        private Task<int> Get(InvocationContext context, CancellationToken cancellationToken)
         {
             var parseResult = context.ParseResult;
             var commandPath = parseResult.GetValue(ExecutableOption);

src/System.CommandLine.Tests/ArgumentTests.cs

@@ -378,7 +378,7 @@ public async Task Custom_argument_parser_is_only_called_once()
                 };
 
                 var command = new RootCommand();
-                command.SetHandler((ctx) => handlerWasCalled = true);
+                command.SetHandler((ctx) => { handlerWasCalled = true; return 0; });
                 command.Options.Add(option);
 
                 await command.InvokeAsync("--value 42");

src/System.CommandLine.Tests/Binding/SetHandlerTests.cs

@@ -16,26 +16,6 @@ namespace System.CommandLine.Tests.Binding
 {
     public class SetHandlerTests
     {
-        [Fact]
-        public async Task Unexpected_return_types_result_in_exit_code_0_if_no_exception_was_thrown()
-        {
-            var wasCalled = false;
-
-            var command = new Command("wat");
-
-            var handle = (InvocationContext ctx, CancellationToken cancellationToken) =>
-            {
-                wasCalled = true;
-                return Task.FromResult(new { NovelType = true });
-            };
-
-            command.SetHandler(handle);
-
-            var exitCode = await command.InvokeAsync("");
-            wasCalled.Should().BeTrue();
-            exitCode.Should().Be(0);
-        }
-
         [Fact]
         public async Task When_User_Requests_Cancellation_Its_Reflected_By_The_Token_Passed_To_Handler()
         {
@@ -47,11 +27,11 @@ public async Task When_User_Requests_Cancellation_Its_Reflected_By_The_Token_Pas
                 try
                 {
                     await Task.Delay(Timeout.InfiniteTimeSpan, cancellationToken);
-                    context.ExitCode = ExpectedExitCode * -1;
+                    return ExpectedExitCode * -1;
                 }
                 catch (OperationCanceledException)
                 {
-                    context.ExitCode = ExpectedExitCode;
+                    return ExpectedExitCode;
                 }
             });
 

src/System.CommandLine.Tests/EnvironmentVariableDirectiveTests.cs

@@ -23,6 +23,7 @@ public async Task Sets_environment_variable_to_value()
             {
                 asserted = true;
                 Environment.GetEnvironmentVariable(variable).Should().Be(value);
+                return 0;
             });
 
             var config = new CommandLineBuilder(rootCommand)
@@ -45,6 +46,7 @@ public async Task Trims_environment_variable_name()
             {
                 asserted = true;
                 Environment.GetEnvironmentVariable(variable).Should().Be(value);
+                return 0;
             });
 
             var config = new CommandLineBuilder(rootCommand)
@@ -67,6 +69,7 @@ public async Task Trims_environment_variable_value()
             {
                 asserted = true;
                 Environment.GetEnvironmentVariable(variable).Should().Be(value);
+                return 0;
             });
 
             var config = new CommandLineBuilder(rootCommand)
@@ -89,6 +92,7 @@ public async Task Sets_environment_variable_value_containing_equals_sign()
             {
                 asserted = true;
                 Environment.GetEnvironmentVariable(variable).Should().Be(value);
+                return 0;
             });
 
             var config = new CommandLineBuilder(rootCommand)
@@ -110,6 +114,7 @@ public async Task Ignores_environment_directive_without_equals_sign()
             {
                 asserted = true;
                 Environment.GetEnvironmentVariable(variable).Should().BeNull();
+                return 0;
             });
 
             var config = new CommandLineBuilder(rootCommand)
@@ -132,6 +137,7 @@ public static async Task Ignores_environment_directive_with_empty_variable_name(
                 asserted = true;
                 var env = Environment.GetEnvironmentVariables();
                 env.Values.Cast<string>().Should().NotContain(value);
+                return 0;
             });
 
             var config = new CommandLineBuilder(rootCommand)
@@ -154,6 +160,7 @@ public static async Task Ignores_environment_directive_with_whitespace_variable_
                 asserted = true;
                 var env = Environment.GetEnvironmentVariables();
                 env.Values.Cast<string>().Should().NotContain(value);
+                return 0;
             });
 
             var config = new CommandLineBuilder(rootCommand)

src/System.CommandLine.Tests/GlobalOptionTests.cs

@@ -29,7 +29,7 @@ public void When_a_required_global_option_is_omitted_it_results_in_an_error()
         {
             var command = new Command("child");
             var rootCommand = new RootCommand { command };
-            command.SetHandler((_) => { });
+            command.SetHandler((_) => 0);
             var requiredOption = new Option<bool>("--i-must-be-set")
             {
                 IsRequired = true,
@@ -69,7 +69,7 @@ public void When_a_required_global_option_is_present_on_child_of_command_it_was_
         {
             var command = new Command("child");
             var rootCommand = new RootCommand { command };
-            command.SetHandler((_) => { });
+            command.SetHandler((_) => 0);
             var requiredOption = new Option<bool>("--i-must-be-set")
             {
                 IsRequired = true,

src/System.CommandLine.Tests/Invocation/CancelOnProcessTerminationTests.cs

@@ -66,10 +66,12 @@ private static Task<int> Program(string[] args)
                     // and reason why we need a timeout on termination processing.
                     CancellationToken token = infiniteDelay ? CancellationToken.None : cancellationToken;
                     await Task.Delay(Timeout.InfiniteTimeSpan, token);
+
+                    return 0;
                 }
                 catch (OperationCanceledException)
                 {
-                    context.ExitCode = GracefulExitCode;
+                    return GracefulExitCode;
                 }
             });
 

src/System.CommandLine.Tests/Invocation/InvocationExtensionsTests.cs

@@ -52,7 +52,7 @@ public async Task RootCommand_InvokeAsync_returns_0_when_handler_is_successful()
             var wasCalled = false;
             var rootCommand = new RootCommand();
 
-            rootCommand.SetHandler((_) => wasCalled = true);
+            rootCommand.SetHandler((_) => { wasCalled = true; return 0; });
 
             var result = await rootCommand.InvokeAsync("");
 
@@ -66,7 +66,7 @@ public void RootCommand_Invoke_returns_0_when_handler_is_successful()
             var wasCalled = false;
             var rootCommand = new RootCommand();
 
-            rootCommand.SetHandler((_) => wasCalled = true);
+            rootCommand.SetHandler((_) => { wasCalled = true; return 0; });
 
             int result = rootCommand.Invoke("");
 
@@ -127,8 +127,7 @@ public async Task RootCommand_InvokeAsync_can_set_custom_result_code()
 
             rootCommand.SetHandler((context, cancellationToken) =>
             {
-                context.ExitCode = 123;
-                return Task.CompletedTask;
+                return Task.FromResult(123);
             });
 
             var resultCode = await rootCommand.InvokeAsync("");
@@ -143,8 +142,7 @@ public void RootCommand_Invoke_can_set_custom_result_code()
 
             rootCommand.SetHandler((context, cancellationToken) =>
             {
-                context.ExitCode = 123;
-                return Task.CompletedTask;
+                return Task.FromResult(123);
             });
 
             int resultCode = rootCommand.Invoke("");

src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs

@@ -39,10 +39,10 @@ public async Task InvokeAsync_chooses_the_appropriate_command()
             var secondWasCalled = false;
 
             var first = new Command("first");
-            first.SetHandler((_) => firstWasCalled = true);
+            first.SetHandler((_) => { firstWasCalled = true; return 0; });
 
             var second = new Command("second");
-            second.SetHandler((_) => secondWasCalled = true);
+            second.SetHandler((_) => { secondWasCalled = true; return 0; });
 
             var config = new CommandLineBuilder(new RootCommand
                          {
@@ -64,10 +64,10 @@ public void Invoke_chooses_the_appropriate_command()
             var secondWasCalled = false;
 
             var first = new Command("first");
-            first.SetHandler((_) => firstWasCalled = true);
+            first.SetHandler((_) => { firstWasCalled = true; return 0; });
 
             var second = new Command("second");
-            second.SetHandler((_) => secondWasCalled = true);
+            second.SetHandler((_) => { secondWasCalled = true; return 0; });
 
             var config = new CommandLineBuilder(new RootCommand
                          {
@@ -350,7 +350,7 @@ public async Task Middleware_can_throw_OperationCancelledException()
                          {
                              throw new OperationCanceledException(cancellationToken);
                          })
-                         .UseExceptionHandler((ex, ctx) => ctx.ExitCode = ex is OperationCanceledException ? 123 : 456)
+                         .UseExceptionHandler((ex, ctx) => ex is OperationCanceledException ? 123 : 456)
                          .Build();
 
             int result = await config.InvokeAsync("the-command");

src/System.CommandLine.Tests/ParserTests.MultiplePositions.cs

@@ -118,7 +118,7 @@ public void A_command_can_be_specified_in_more_than_one_position(
                 string expectedParent)
             {
                 var reusedCommand = new Command("reused");
-                reusedCommand.SetHandler((_) => { });
+                reusedCommand.SetHandler((_) => 0);
                 reusedCommand.Add(new Option<string>("--the-option"));
 
                 var outer = new Command("outer")