[src] Propagate the [CCallback] and [BlockCallback] attributes to generated code. (#20225)

The generator needs these attributes in certain cases when a third-party library implements a protocol that subclasses a platform protocol where members of the platform protocol has members with parameters with these attributes.

That's a rather long sentence: in fact there are fewer words in the test verifying this behavior!

src/ObjCRuntime/BlockCallbackAttribute.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace ObjCRuntime {
+	/// <summary>
+	/// This attribute is applied to delegate parameters in a delegate to specify
+	/// that the delegate parameter needs an Objective-C Block-style bridge.
+	/// </summary>
+	/// <remarks>
+	/// <seealso cref='T:ObjCRuntime.CCallbackAttribute' />
+	/// </remarks>
+	[AttributeUsage (AttributeTargets.Parameter, AllowMultiple = false)]
+	public class BlockCallbackAttribute : Attribute {
+		/// <summary>
+		/// Initializes a new instance of the <see cref="BlockCallbackAttribute"/> class.
+		/// </summary>
+		public BlockCallbackAttribute ()
+		{
+		}
+	}
+}

src/ObjCRuntime/CCallbackAttribute.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace ObjCRuntime {
+	/// <summary>
+	/// This attribute is applied to delegate parameters in a delegate to specify
+	/// that the delegate parameter needs an C-style bridge.
+	/// </summary>
+	/// <remarks>
+	/// <seealso cref='T:ObjCRuntime.BlockCallbackAttribute' />
+	/// </remarks> 
+	[AttributeUsage (AttributeTargets.Parameter, AllowMultiple = false)]
+	public class CCallbackAttribute : Attribute {
+		/// <summary>
+		/// Initializes a new instance of the <see cref="CCallbackAttribute"/> class.
+		/// </summary>
+		public CCallbackAttribute ()
+		{
+		}
+	}
+}

src/bgen/Attributes.cs

@@ -368,18 +368,6 @@ public class AlignAttribute : Attribute {
 public class ParamsAttribute : Attribute {
 }
 
-//
-// These two attributes can be applied to parameters in a C# delegate
-// declaration to specify what kind of bridge needs to be provided on
-// callback.   Either a Block style setup, or a C-style setup
-//
-[AttributeUsage (AttributeTargets.Parameter, AllowMultiple = false)]
-public class BlockCallbackAttribute : Attribute { }
-
-[AttributeUsage (AttributeTargets.Parameter, AllowMultiple = false)]
-public class CCallbackAttribute : Attribute { }
-
-
 //
 // When applied, flags the [Flags] as a notification and generates the
 // code to strongly type the notification.

src/bgen/Generator.cs

@@ -6813,12 +6813,17 @@ public partial class Generator : IMemberGatherer {
 	{
 		var pt = p.ParameterType;
 
-		string name;
+		string name = string.Empty;
+		if (AttributeManager.HasAttribute<BlockCallbackAttribute> (p))
+			name = "[BlockCallback] ";
+		else if (AttributeManager.HasAttribute<CCallbackAttribute> (p))
+			name = "[CCallback] ";
+
 		if (pt.IsByRef) {
 			pt = pt.GetElementType ();
-			name = (removeRefTypes ? "" : (p.IsOut ? "out " : "ref ")) + TypeManager.RenderType (pt, p);
+			name += (removeRefTypes ? "" : (p.IsOut ? "out " : "ref ")) + TypeManager.RenderType (pt, p);
 		} else
-			name = TypeManager.RenderType (pt, p);
+			name += TypeManager.RenderType (pt, p);
 		if (!pt.IsValueType && AttributeManager.HasAttribute<NullAllowedAttribute> (p))
 			name += "?";
 		return name;

src/bgen/bgen.csproj

@@ -47,6 +47,8 @@
     <Compile Include="$(RepositoryPath)\src\ObjCRuntime\ArgumentSemantic.cs" />
     <Compile Include="$(RepositoryPath)\src\ObjCRuntime\BindAsAttribute.cs" />
     <Compile Include="$(RepositoryPath)\src\ObjCRuntime\BindingImplAttribute.cs" />
+    <Compile Include="$(RepositoryPath)\src\ObjCRuntime\BlockCallbackAttribute.cs" />
+    <Compile Include="$(RepositoryPath)\src\ObjCRuntime\CCallbackAttribute.cs" />
     <Compile Include="$(RepositoryPath)\src\ObjCRuntime\LinkWithAttribute.cs" />
     <Compile Include="$(RepositoryPath)\src\ObjCRuntime\NativeAttribute.cs" />
     <Compile Include="$(RepositoryPath)\src\ObjCRuntime\NativeNameAttribute.cs" />

src/frameworks.sources

@@ -1928,6 +1928,8 @@ SHARED_CORE_SOURCES = \
 	ObjCRuntime/ArgumentSemantic.cs \
 	ObjCRuntime/BindAsAttribute.cs \
 	ObjCRuntime/Blocks.cs \
+	ObjCRuntime/BlockCallbackAttribute.cs \
+	ObjCRuntime/CCallbackAttribute.cs \
 	ObjCRuntime/Class.cs \
 	ObjCRuntime/Constants.cs \
 	ObjCRuntime/DisposableObject.cs \

src/generator.csproj

@@ -133,6 +133,8 @@
     <Compile Include="..\src\ObjCRuntime\ArgumentSemantic.cs" />
     <Compile Include="..\src\ObjCRuntime\BindAsAttribute.cs" />
     <Compile Include="..\src\ObjCRuntime\BindingImplAttribute.cs" />
+    <Compile Include="..\src\ObjCRuntime\BlockCallbackAttribute.cs" />
+    <Compile Include="..\src\ObjCRuntime\CCallbackAttribute.cs" />
     <Compile Include="..\src\ObjCRuntime\LinkWithAttribute.cs" />
     <Compile Include="..\src\ObjCRuntime\NativeAttribute.cs" />
     <Compile Include="..\src\ObjCRuntime\NativeNameAttribute.cs" />

tests/generator/BGenTests.cs

@@ -1434,6 +1434,12 @@ namespace GeneratorTests {
 			BuildFile (Profile.iOS, "tests/internal-delegate.cs");
 		}
 
+		[Test]
+		public void DelegateParameterAttributes ()
+		{
+			BuildFile (Profile.iOS, "tests/delegate-parameter-attributes.cs");
+		}
+
 #if NET
 		[Test]
 		public void Issue19612 ()

tests/generator/tests/delegate-parameter-attributes.cs

@@ -0,0 +1,6 @@
+using Foundation;
+
+namespace Test {
+	[Protocol]
+	interface DerivedProtocol : INSFilePresenter { }
+}