Improve automatic cloning of MediaTypeFormatter. Resolves #156.

Author: Chris Martinez

src/Microsoft.AspNet.WebApi.Versioning.ApiExplorer/Description/ApiVersionParameterDescriptionContext.cs

@@ -6,11 +6,11 @@
     using System.Linq;
     using System.Net.Http.Formatting;
     using System.Net.Http.Headers;
+    using System.Web.Http;
     using System.Web.Http.Description;
     using static Microsoft.Web.Http.Versioning.ApiVersionParameterLocation;
-    using static System.Web.Http.Description.ApiParameterSource;
     using static System.StringComparison;
-    using System.Web.Http;
+    using static System.Web.Http.Description.ApiParameterSource;
 
     /// <summary>
     /// Represents an object that contains API version parameter descriptions.

src/Microsoft.AspNet.WebApi.Versioning.ApiExplorer/LocalSR.Designer.cs

@@ -121,6 +121,6 @@
     <value>The requested API version</value>
   </data>
   <data name="MediaTypeFormatterNotCloneable" xml:space="preserve">
-    <value>The media type formatter {0} could not be cloned. The type must either implement {1} or define a copy constructor with the signature '{0}({0} formatter)'.</value>
+    <value>The media type formatter {0} could not be cloned. The type must either implement {1}, define a copy constructor with the signature '{0}({0} formatter)', or have a parameterless constructor.</value>
   </data>
 </root>

src/Microsoft.AspNet.WebApi.Versioning.ApiExplorer/LocalSR.resx

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
  <PropertyGroup>
-  <VersionPrefix>1.0.0</VersionPrefix>
+  <VersionPrefix>1.0.1</VersionPrefix>
   <AssemblyVersion>1.0.0.0</AssemblyVersion>
   <TargetFramework>net45</TargetFramework>
   <AssemblyName>Microsoft.AspNet.WebApi.Versioning.ApiExplorer</AssemblyName>
@@ -10,7 +10,7 @@
   <RootNamespace>Microsoft.Web.Http</RootNamespace>
   <DefineConstants>$(DefineConstants);WEBAPI</DefineConstants>
   <PackageTags>Microsoft;AspNet;AspNetWebAPI;Versioning;ApiExplorer</PackageTags>
-  <PackageReleaseNotes></PackageReleaseNotes>
+  <PackageReleaseNotes>• Improve cloning of MediaTypeFormatter (Issue #156)</PackageReleaseNotes>
  </PropertyGroup>
 
  <ItemGroup>

src/Microsoft.AspNet.WebApi.Versioning.ApiExplorer/Microsoft.AspNet.WebApi.Versioning.ApiExplorer.csproj

@@ -7,10 +7,9 @@
     using System.Diagnostics.Contracts;
     using System.Linq;
     using System.Net.Http.Formatting;
-    using System.Reflection;
-    using static System.Reflection.BindingFlags;
     using static System.Linq.Expressions.Expression;
     using static System.Net.Http.Headers.MediaTypeHeaderValue;
+    using static System.Reflection.BindingFlags;
 
     static class MediaTypeFormatterAdapterFactory
     {
@@ -42,21 +41,55 @@ static Func<MediaTypeFormatter, MediaTypeFormatter> NewCloneFunction( Type type
             Contract.Requires( type != null );
             Contract.Ensures( Contract.Result<Func<MediaTypeFormatter, MediaTypeFormatter>>() != null );
 
-            var clone = NewActivator( type );
+            var clone = NewCopyConstructorActivator( type ) ??
+                        NewParameterlessConstructorActivator( type ) ??
+                        throw new InvalidOperationException( LocalSR.MediaTypeFormatterNotCloneable.FormatDefault( type.Name, typeof( ICloneable ).Name ) );
+
             return instance => CloneMediaTypes( clone( instance ) );
         }
 
-        static Func<MediaTypeFormatter, MediaTypeFormatter> NewActivator( Type type )
+        static Func<MediaTypeFormatter, MediaTypeFormatter> NewCopyConstructorActivator( Type type )
+        {
+            Contract.Requires( type != null );
+
+            var constructors = from ctor in type.GetConstructors( Public | NonPublic | Instance )
+                               let args = ctor.GetParameters()
+                               where args.Length == 1 && type.Equals( args[0].ParameterType )
+                               select ctor;
+            var constructor = constructors.SingleOrDefault();
+
+            if ( constructor == null )
+            {
+                return null;
+            }
+
+            var formatter = Parameter( typeof( MediaTypeFormatter ), "formatter" );
+            var @new = New( constructor, Convert( formatter, type ) );
+            var lambda = Lambda<Func<MediaTypeFormatter, MediaTypeFormatter>>( @new, formatter );
+
+            return lambda.Compile();  // formatter => new MediaTypeFormatter( formatter );
+        }
+
+        static Func<MediaTypeFormatter, MediaTypeFormatter> NewParameterlessConstructorActivator( Type type )
         {
             Contract.Requires( type != null );
-            Contract.Ensures( Contract.Result<Func<MediaTypeFormatter, MediaTypeFormatter>>() != null );
 
-            var ctor = ResolveConstructor( type );
+            var constructors = from ctor in type.GetConstructors( Public | NonPublic | Instance )
+                               let args = ctor.GetParameters()
+                               where args.Length == 0
+                               select ctor;
+            var constructor = constructors.SingleOrDefault();
+
+            if ( constructor == null )
+            {
+                return null;
+            }
+
             var formatter = Parameter( typeof( MediaTypeFormatter ), "formatter" );
-            var @new = New( ctor, Convert( formatter, type ) );
+            var @new = New( constructor );
             var lambda = Lambda<Func<MediaTypeFormatter, MediaTypeFormatter>>( @new, formatter );
 
-            return lambda.Compile();
+            return lambda.Compile(); // formatter => new MediaTypeFormatter();
         }
 
         static MediaTypeFormatter CloneMediaTypes( MediaTypeFormatter instance )
@@ -75,21 +108,5 @@ static MediaTypeFormatter CloneMediaTypes( MediaTypeFormatter instance )
 
             return instance;
         }
-
-        static ConstructorInfo ResolveConstructor( Type type )
-        {
-            var constructors = from ctor in type.GetConstructors( Public | NonPublic | Instance )
-                               let args = ctor.GetParameters()
-                               where args.Length == 1 && type.Equals( args[0].ParameterType )
-                               select ctor;
-            var constructor = constructors.SingleOrDefault();
-
-            if ( constructor == null )
-            {
-                throw new InvalidOperationException( LocalSR.MediaTypeFormatterNotCloneable.FormatDefault( type.Name, typeof( ICloneable ).Name ) );
-            }
-
-            return constructor;
-        }
     }
 }

src/Microsoft.AspNet.WebApi.Versioning.ApiExplorer/System.Web.Http/MediaTypeFormatterAdapterFactory.cs

@@ -170,11 +170,13 @@ public void add_parameter_should_add_descriptor_for_media_type_parameter()
             // arrange
             var configuration = new HttpConfiguration();
             var json = new JsonMediaTypeFormatter();
+            var formUrlEncoded = new FormUrlEncodedMediaTypeFormatter();
 
             configuration.Formatters.Clear();
             configuration.Formatters.Add( json );
+            configuration.Formatters.Add( formUrlEncoded );
 
-            var description = new ApiDescription() { SupportedResponseFormatters = { json } };
+            var description = new ApiDescription() { SupportedRequestBodyFormatters = { json, formUrlEncoded } };
             var version = new ApiVersion( 1, 0 );
             var options = new ApiExplorerOptions( configuration );
             var context = new ApiVersionParameterDescriptionContext( description, version, options );
@@ -183,14 +185,22 @@ public void add_parameter_should_add_descriptor_for_media_type_parameter()
             context.AddParameter( "v", MediaTypeParameter );
 
             // assert
-            var formatter = description.SupportedResponseFormatters.Single();
+            var formatter = description.SupportedRequestBodyFormatters[0];
 
             foreach ( var mediaType in formatter.SupportedMediaTypes )
             {
                 mediaType.Parameters.Single().Should().Be( new NameValueHeaderValue( "v", "1.0" ) );
             }
 
             formatter.Should().NotBeSameAs( json );
+            formatter = description.SupportedRequestBodyFormatters[1];
+
+            foreach ( var mediaType in formatter.SupportedMediaTypes )
+            {
+                mediaType.Parameters.Single().Should().Be( new NameValueHeaderValue( "v", "1.0" ) );
+            }
+
+            formatter.Should().NotBeSameAs( formUrlEncoded );
         }
 
         [Fact]