Perf improvements part 6: startup time

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

@@ -98,6 +98,7 @@
   public class ModelBindingCommandHandler, System.CommandLine.Invocation.ICommandHandler
     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)
     public System.Threading.Tasks.Task<System.Int32> InvokeAsync(System.CommandLine.Invocation.InvocationContext context)
   public class ModelDescriptor
     public static ModelDescriptor FromType<T>()

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

@@ -356,6 +356,7 @@ System.CommandLine.Help
     public System.Int32 GetHashCode()
 System.CommandLine.Invocation
   public interface ICommandHandler
+    public System.Int32 Invoke(InvocationContext context)
     public System.Threading.Tasks.Task<System.Int32> InvokeAsync(InvocationContext context)
   public interface IInvocationResult
     public System.Void Apply(InvocationContext context)
@@ -498,7 +499,7 @@ System.CommandLine.Parsing
     public T GetValueForOption<T>(Option<T> option)
     public System.Object GetValueForOption(System.CommandLine.Option option)
     public System.String ToString()
-  public struct Token : System.ValueType, System.IEquatable<Token>
+  public class Token, System.IEquatable<Token>
     public static System.Boolean op_Equality(Token left, Token right)
     public static System.Boolean op_Inequality(Token left, Token right)
     .ctor(System.String value, TokenType type, System.CommandLine.Symbol symbol)

src/System.CommandLine.Benchmarks/System.CommandLine.Benchmarks.csproj

@@ -9,8 +9,8 @@
     <UseSharedCompilation>false</UseSharedCompilation>
 
     <!-- Supported target frameworks -->
-    <TargetFrameworks Condition="'$(TargetFrameworks)' == '' AND '$(OS)' == 'Windows_NT'">net461;net5.0;</TargetFrameworks>
-    <TargetFrameworks Condition="'$(TargetFrameworks)' == ''">net5.0;</TargetFrameworks>
+    <TargetFrameworks Condition="'$(TargetFrameworks)' == '' AND '$(OS)' == 'Windows_NT'">net461;net5.0;net6.0;</TargetFrameworks>
+    <TargetFrameworks Condition="'$(TargetFrameworks)' == ''">net5.0;net6.0;</TargetFrameworks>
 
     <!-- This repo does not produce any libraries, therefore generating docs is disabled -->
     <GenerateDocumentationFile>False</GenerateDocumentationFile>

src/System.CommandLine.Generator/CommandHandlerSourceGenerator.cs

@@ -114,6 +114,9 @@ private class GeneratedHandler_{handlerCount} : {ICommandHandlerType}
             {propertyDeclaration}");
             }
 
+            builder.Append($@"
+            public int Invoke(global::System.CommandLine.Invocation.InvocationContext context) => InvokeAsync(context).GetAwaiter().GetResult();");
+
             builder.Append($@"
             public async global::System.Threading.Tasks.Task<int> InvokeAsync(global::System.CommandLine.Invocation.InvocationContext context)
             {{");

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

@@ -132,6 +132,12 @@ 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)
+                {
+                    service.Value = IntOption;
+                    return IntOption;
+                }
+
                 public Task<int> InvokeAsync(InvocationContext context)
                 {
                     service.Value = IntOption;
@@ -162,6 +168,8 @@ public MyHandler(MyService service)
 
                 public string One { get; set; }
 
+                public int Invoke(InvocationContext context) => InvokeAsync(context).GetAwaiter().GetResult();
+
                 public Task<int> InvokeAsync(InvocationContext context)
                 {
                     service.Value = IntOption;

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

@@ -446,6 +446,8 @@ public abstract class AbstractTestCommandHandler : ICommandHandler
     {
         public abstract Task<int> DoJobAsync();
 
+        public int Invoke(InvocationContext context) => InvokeAsync(context).GetAwaiter().GetResult();
+
         public Task<int> InvokeAsync(InvocationContext context)
             => DoJobAsync();
     }
@@ -458,6 +460,8 @@ public override Task<int> DoJobAsync()
 
     public class VirtualTestCommandHandler : ICommandHandler
     {
+        public int Invoke(InvocationContext context) => 42;
+
         public virtual Task<int> InvokeAsync(InvocationContext context)
             => Task.FromResult(42);
     }

src/System.CommandLine.NamingConventionBinder/ModelBindingCommandHandler.cs

@@ -128,4 +128,6 @@ private void BindValueSource(ParameterInfo param, IValueSource valueSource)
                : _methodDescriptor.ParameterDescriptors
                                   .FirstOrDefault(x => x.ValueName == param.Name &&
                                                        x.ValueType == param.ParameterType);
+
+    public int Invoke(InvocationContext context) => InvokeAsync(context).GetAwaiter().GetResult();
 }

src/System.CommandLine/ArgumentArity.cs

@@ -72,7 +72,7 @@ public bool Equals(ArgumentArity other) =>
         public override int GetHashCode()
             => MaximumNumberOfValues ^ MinimumNumberOfValues ^ IsNonDefault.GetHashCode();
 
-        internal static FailedArgumentConversionArityResult? Validate(
+        internal static ArgumentConversionResult? Validate(
             SymbolResult symbolResult,
             Argument argument,
             int minimumNumberOfValues,
@@ -93,9 +93,10 @@ public override int GetHashCode()
                     return null;
                 }
 
-                return new MissingArgumentConversionResult(
+                return ArgumentConversionResult.Failure(
                     argument,
-                    symbolResult.LocalizationResources.RequiredArgumentMissing(symbolResult));
+                    symbolResult.LocalizationResources.RequiredArgumentMissing(symbolResult),
+                    ArgumentConversionResultType.FailedMissingArgument);
             }
 
             if (tokenCount > maximumNumberOfValues)
@@ -104,9 +105,10 @@ public override int GetHashCode()
                 {
                     if (!optionResult.Option.AllowMultipleArgumentsPerToken)
                     {
-                        return new TooManyArgumentsConversionResult(
+                        return ArgumentConversionResult.Failure(
                             argument,
-                            symbolResult!.LocalizationResources.ExpectsOneArgument(symbolResult));
+                            symbolResult!.LocalizationResources.ExpectsOneArgument(symbolResult),
+                            ArgumentConversionResultType.FailedTooManyArguments);
                     }
                 }
             }

src/System.CommandLine/Binding/ArgumentConversionResult.cs

@@ -1,23 +1,73 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+using System.Linq;
+
 namespace System.CommandLine.Binding
 {
-    internal abstract class ArgumentConversionResult
+    internal sealed class ArgumentConversionResult
     {
-        private protected ArgumentConversionResult(Argument argument)
+        internal readonly Argument Argument;
+        internal readonly object? Value;
+        internal readonly string? ErrorMessage;
+        internal ArgumentConversionResultType Result;
+
+        private ArgumentConversionResult(Argument argument, string error, ArgumentConversionResultType failure)
+        {
+            Argument = argument ?? throw new ArgumentNullException(nameof(argument));
+            ErrorMessage = error ?? throw new ArgumentNullException(nameof(error));
+            Result = failure;
+        }
+
+        private ArgumentConversionResult(Argument argument, object? value)
+        {
+            Argument = argument ?? throw new ArgumentNullException(nameof(argument));
+            Value = value;
+            Result = ArgumentConversionResultType.Successful;
+        }
+
+        private ArgumentConversionResult(Argument argument)
         {
             Argument = argument ?? throw new ArgumentNullException(nameof(argument));
+            Result = ArgumentConversionResultType.NoArgument;
+        }
+
+        internal ArgumentConversionResult(
+            Argument argument,
+            Type expectedType,
+            string value,
+            LocalizationResources localizationResources) :
+            this(argument, FormatErrorMessage(argument, expectedType, value, localizationResources), ArgumentConversionResultType.FailedType)
+        {
         }
 
-        public Argument Argument { get; }
+        internal static ArgumentConversionResult Failure(Argument argument, string error, ArgumentConversionResultType reason) => new(argument, error, reason);
+
+        public static ArgumentConversionResult Success(Argument argument, object? value) => new(argument, value);
 
-        internal string? ErrorMessage { get; set; }
+        internal static ArgumentConversionResult None(Argument argument) => new(argument);
 
-        internal static FailedArgumentConversionResult Failure(Argument argument, string error) => new(argument, error);
+        private static string FormatErrorMessage(
+            Argument argument,
+            Type expectedType,
+            string value,
+            LocalizationResources localizationResources)
+        {
+            if (argument.FirstParent?.Symbol is IdentifierSymbol identifierSymbol &&
+                argument.FirstParent.Next is null)
+            {
+                var alias = identifierSymbol.Aliases.First();
 
-        public static SuccessfulArgumentConversionResult Success(Argument argument, object? value) => new(argument, value);
+                switch (identifierSymbol)
+                {
+                    case Command _:
+                        return localizationResources.ArgumentConversionCannotParseForCommand(value, alias, expectedType);
+                    case Option _:
+                        return localizationResources.ArgumentConversionCannotParseForOption(value, alias, expectedType);
+                }
+            }
 
-        internal static NoArgumentConversionResult None(Argument argument) => new(argument);
+            return localizationResources.ArgumentConversionCannotParse(value, expectedType);
+        }
     }
 }

src/System.CommandLine/Binding/ArgumentConversionResultType.cs

@@ -0,0 +1,16 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace System.CommandLine.Binding
+{
+    internal enum ArgumentConversionResultType
+    {
+        NoArgument, // NoArgumentConversionResult
+        Successful, // SuccessfulArgumentConversionResult
+        Failed, // FailedArgumentConversionResult
+        FailedArity, // FailedArgumentConversionArityResult
+        FailedType, // FailedArgumentTypeConversionResult
+        FailedTooManyArguments, // TooManyArgumentsConversionResult
+        FailedMissingArgument, // MissingArgumentConversionResult
+    }
+}

src/System.CommandLine/Binding/ArgumentConverter.DefaultValues.cs

@@ -4,7 +4,6 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.Linq;
 using System.Reflection;
 using System.Runtime.Serialization;
 
@@ -13,10 +12,7 @@ namespace System.CommandLine.Binding;
 internal static partial class ArgumentConverter
 {
 #if NET6_0_OR_GREATER
-    private static readonly Lazy<ConstructorInfo> _listCtor =
-        new(() => typeof(List<>)
-                  .GetConstructors()
-                  .SingleOrDefault(c => c.GetParameters().Length == 0)!);
+    private static ConstructorInfo? _listCtor;
 #endif
 
     private static Array CreateEmptyArray(Type itemType, int capacity = 0)
@@ -25,14 +21,19 @@ private static Array CreateEmptyArray(Type itemType, int capacity = 0)
     private static IList CreateEmptyList(Type listType)
     {
 #if NET6_0_OR_GREATER
-        var ctor = (ConstructorInfo)listType.GetMemberWithSameMetadataDefinitionAs(_listCtor.Value);
+        ConstructorInfo? listCtor = _listCtor;
+
+        if (listCtor is null)
+        {
+            _listCtor = listCtor = typeof(List<>).GetConstructor(Type.EmptyTypes)!;
+        }
+
+        var ctor = (ConstructorInfo)listType.GetMemberWithSameMetadataDefinitionAs(listCtor);
 #else
-        var ctor = listType
-                   .GetConstructors()
-                   .SingleOrDefault(c => c.GetParameters().Length == 0);
+        var ctor = listType.GetConstructor(Type.EmptyTypes);
 #endif
 
-        return (IList)ctor.Invoke(new object[] { });
+        return (IList)ctor.Invoke(null);
     }
 
     private static IList CreateEnumerable(Type type, Type itemType, int capacity = 0)