Add explicit GUID support for delegates and non-synthesized interfaces.

src/Authoring/WinRT.SourceGenerator/WinRTTypeWriter.cs

@@ -1574,15 +1574,8 @@ private void AddOverloadAttributeForInterfaceMethods(TypeDeclaration interfaceTy
             }
         }
 
-        private void AddGuidAttribute(EntityHandle parentHandle, string name)
+        private void AddGuidAttribute(EntityHandle parentHandle, Guid guid)
         {
-            Guid guid;
-            using (SHA1 sha = new SHA1CryptoServiceProvider())
-            {
-                var hash = sha.ComputeHash(Encoding.UTF8.GetBytes(name));
-                guid = Helper.EncodeGuid(hash);
-            }
-
             var uint32Type = Model.Compilation.GetTypeByMetadataName("System.UInt32");
             var uint16Type = Model.Compilation.GetTypeByMetadataName("System.UInt16");
             var byteType = Model.Compilation.GetTypeByMetadataName("System.Byte");
@@ -1620,6 +1613,33 @@ private void AddGuidAttribute(EntityHandle parentHandle, string name)
             AddCustomAttributes("Windows.Foundation.Metadata.GuidAttribute", types, arguments, parentHandle);
         }
 
+        private void AddGuidAttribute(EntityHandle parentHandle, string name)
+        {
+            Guid guid;
+            using (SHA1 sha = new SHA1CryptoServiceProvider())
+            {
+                var hash = sha.ComputeHash(Encoding.UTF8.GetBytes(name));
+                guid = Helper.EncodeGuid(hash);
+            }
+
+            AddGuidAttribute(parentHandle, guid);
+        }
+
+        private void AddGuidAttribute(EntityHandle parentHandle, ISymbol symbol)
+        {
+            if (symbol.TryGetAttributeWithType(Model.Compilation.GetTypeByMetadataName("System.Runtime.InteropServices.GuidAttribute"), out AttributeData guidAttribute)
+                    && guidAttribute is { ConstructorArguments.IsDefaultOrEmpty: false }
+                    && guidAttribute.ConstructorArguments[0].Value is string guidString
+                    && Guid.TryParse(guidString, out Guid guid))
+            {
+                AddGuidAttribute(parentHandle, guid);
+            }
+            else
+            {
+                AddGuidAttribute(parentHandle, symbol.ToString());
+            }
+        }
+
         private void AddCustomAttributes(
             string attributeTypeName,
             IList<ITypeSymbol> primitiveTypes,
@@ -1795,7 +1815,7 @@ public override void VisitDelegateDeclaration(DelegateDeclarationSyntax node)
             currentTypeDeclaration.Handle = typeDefinitionHandle;
             typeDefinitionMapping[QualifiedName(symbol, true)] = currentTypeDeclaration;
 
-            AddGuidAttribute(typeDefinitionHandle, symbol.ToString());
+            AddGuidAttribute(typeDefinitionHandle, symbol);
         }
 
         public void AddEventDeclaration(string eventName, ITypeSymbol eventType, ISymbol symbol, bool isStatic, bool isInterfaceParent, bool isPublic = true)
@@ -2068,7 +2088,7 @@ void AddComponentType(INamedTypeSymbol type, Action visitTypeDeclaration = null)
 
             if (isInterface)
             {
-                AddGuidAttribute(typeDefinitionHandle, type.ToString());
+                AddGuidAttribute(typeDefinitionHandle, type);
                 AddOverloadAttributeForInterfaceMethods(typeDeclaration);
             }
 
@@ -2791,4 +2811,4 @@ public static string QualifiedName(ISymbol symbol, bool includeGenerics = false)
             return QualifiedName(symbol.ContainingNamespace.ToString(), GetGenericName(symbol, includeGenerics));
         }
     }
-}
+}

src/Tests/AuthoringConsumptionTest/AuthoringConsumptionTest.exe.manifest

@@ -82,5 +82,9 @@
        name="AuthoringTest.CustomXamlMetadataProvider"
        threadingModel="both"
        xmlns="urn:schemas-microsoft-com:winrt.v1" />
+     <activatableClass
+       name="AuthoringTest.CustomInterfaceGuidClass"
+       threadingModel="both"
+       xmlns="urn:schemas-microsoft-com:winrt.v1" />
   </file>
-</assembly>
+</assembly>

src/Tests/AuthoringConsumptionTest/test.cpp

@@ -722,4 +722,17 @@ TEST(AuthoringTest, XamlMetadataProvider)
     EXPECT_NE(provider.GetXamlType(winrt::xaml_typename<Windows::Foundation::IReference<Windows::Foundation::TimeSpan>>()), nullptr);
     EXPECT_NE(provider.GetXamlType(winrt::xaml_typename<Windows::Foundation::IReference<BasicEnum>>()), nullptr);
     EXPECT_NE(provider.GetXamlType(winrt::xaml_typename<Windows::Foundation::IReference<FlagsEnum>>()), nullptr);
+}
+
+TEST(AuthoringTest, CustomInterfaceGuid)
+{
+    CustomInterfaceGuidClass customInterfaceGuidClass;
+    winrt::com_ptr<::IUnknown> customInterfaceClassUnknown = customInterfaceGuidClass.as<::IUnknown>();
+    ICustomInterfaceGuid customInterface;
+
+    IID customInterfaceIid;
+    check_hresult(IIDFromString(L"{26D8EE57-8B1B-46F4-A4F9-8C6DEEEAF53A}", &customInterfaceIid));
+    check_hresult(customInterfaceClassUnknown->QueryInterface(customInterfaceIid, reinterpret_cast<void**>(winrt::put_abi(customInterface))));
+
+    EXPECT_EQ(customInterface.HelloWorld(), L"Hello World!");
 }

src/Tests/AuthoringTest/Program.cs

@@ -1854,6 +1854,17 @@ private static int GetNumberFromAbi(void* thisPtr, int* value)
             }
         }
     }
+
+    [System.Runtime.InteropServices.Guid("26D8EE57-8B1B-46F4-A4F9-8C6DEEEAF53A")]
+    public interface ICustomInterfaceGuid
+    {
+        string HelloWorld();
+    }
+
+    public sealed class CustomInterfaceGuidClass : ICustomInterfaceGuid
+    {
+        public string HelloWorld() => "Hello World!";
+    }
 }
 
 namespace ABI.AuthoringTest