😤 Correct fix for immutable handling

gsscoder · gsscoder · commit 68c8460372eb · 2015-07-02T20:33:09.000+02:00
diff --git a/src/CommandLine.Tests/Unit/ParserTests.cs b/src/CommandLine.Tests/Unit/ParserTests.cs
@@ -200,5 +200,21 @@ public void Explicit_help_request_with_immutable_instance_generates_help_request
             result.Errors.Should().ContainSingle(e => e.Equals(expectedError));
             // Teardown
         }
+
+        [Fact]
+        public void Explicit_help_request_with_immutable_instance_generates_help_screen()
+        {
+            // Fixture setup
+            var help = new StringWriter();
+            var sut = new Parser(config => config.HelpWriter = help);
+
+            // Exercize system
+            sut.ParseArguments<FakeImmutableOptions>(new[] { "--help" });
+            var result = help.ToString();
+
+            // Verify outcome
+            result.Length.Should().BeGreaterThan(0);
+            // Teardown
+        }
     }
 }
diff --git a/src/CommandLine/Core/InstanceBuilder.cs b/src/CommandLine/Core/InstanceBuilder.cs
@@ -50,11 +50,17 @@ public static ParserResult<T> Build<T>(
                 .ThrowingValidate(SpecificationGuards.Lookup)
                 .OfType<OptionSpecification>();
 
+            Func<T> makeDefault = () =>
+                typeof(T).IsMutable()
+                    ? factory.Return(f => f(), Activator.CreateInstance<T>())
+                    : ReflectionHelper.CreateDefaultImmutableInstance<T>(
+                        (from p in specProps select p.Specification.ConversionType).ToArray());
+
             if (arguments.Any() && nameComparer.Equals("--help", arguments.First()))
             {
                 return ParserResult.Create(
                     ParserResultType.Options,
-                    factory.Return(f => f(), default(T)),
+                    makeDefault(),
                     new[] { new HelpRequestedError() });
             }
 
diff --git a/src/CommandLine/Infrastructure/ReflectionHelper.cs b/src/CommandLine/Infrastructure/ReflectionHelper.cs
@@ -3,6 +3,7 @@
 using System;
 using System.Linq;
 using System.Reflection;
+using CommandLine.Core;
 
 namespace CommandLine.Infrastructure
 {
@@ -36,5 +37,14 @@ public static bool IsFSharpOptionType(Type type)
             return type.FullName.StartsWith(
                 "Microsoft.FSharp.Core.FSharpOption`1", StringComparison.Ordinal);
         }
+
+        public static T CreateDefaultImmutableInstance<T>(Type[] constructorTypes)
+        {
+            var t = typeof(T);
+            var ctor = t.GetConstructor(constructorTypes);
+            var values = (from prms in ctor.GetParameters()
+                          select prms.ParameterType.CreateDefaultForImmutable()).ToArray();
+            return (T)ctor.Invoke(values);
+        }
     }
 }
diff --git a/src/CommandLine/ParserResult.cs b/src/CommandLine/ParserResult.cs
@@ -105,6 +105,7 @@ public static ParserResult<T> Create<T>(ParserResultType tag, T instance, IEnume
 
         public static ParserResult<T> Create<T>(ParserResultType tag, T instance, IEnumerable<Error> errors, Maybe<IEnumerable<Type>> verbTypes)
         {
+            if (Equals(instance, default(T))) throw new ArgumentNullException("instance");
             if (errors == null) throw new ArgumentNullException("errors");
             if (verbTypes == null) throw new ArgumentNullException("verbTypes");
 

Original file line number	Diff line number	Diff line change
`@@ -3,6 +3,7 @@`
`3`	`3`	`using System;`
`4`	`4`	`using System.Linq;`
`5`	`5`	`using System.Reflection;`
	`6`	`+using CommandLine.Core;`
`6`	`7`
`7`	`8`	`namespace CommandLine.Infrastructure`
`8`	`9`	`{`
`@@ -36,5 +37,14 @@ public static bool IsFSharpOptionType(Type type)`
`36`	`37`	`return type.FullName.StartsWith(`
`37`	`38`	"Microsoft.FSharp.Core.FSharpOption`1", StringComparison.Ordinal);
`38`	`39`	`}`
	`40`	`+`
	`41`	`+ public static T CreateDefaultImmutableInstance<T>(Type[] constructorTypes)`
	`42`	`+ {`
	`43`	`+ var t = typeof(T);`
	`44`	`+ var ctor = t.GetConstructor(constructorTypes);`
	`45`	`+ var values = (from prms in ctor.GetParameters()`
	`46`	`+ select prms.ParameterType.CreateDefaultForImmutable()).ToArray();`
	`47`	`+ return (T)ctor.Invoke(values);`
	`48`	`+ }`
`39`	`49`	`}`
`40`	`50`	`}`
Original file line number	Diff line number	Diff line change
`@@ -105,6 +105,7 @@ public static ParserResult<T> Create<T>(ParserResultType tag, T instance, IEnume`
`105`	`105`
`106`	`106`	`public static ParserResult<T> Create<T>(ParserResultType tag, T instance, IEnumerable<Error> errors, Maybe<IEnumerable<Type>> verbTypes)`
`107`	`107`	`{`
	`108`	`+ if (Equals(instance, default(T))) throw new ArgumentNullException("instance");`
`108`	`109`	`if (errors == null) throw new ArgumentNullException("errors");`
`109`	`110`	`if (verbTypes == null) throw new ArgumentNullException("verbTypes");`
`110`	`111`