Fix NativeMarshalling attribute override for COM interfaces

src/libraries/System.Runtime.InteropServices/gen/Microsoft.Interop.SourceGeneration/MarshallingInfoParser.cs

@@ -239,28 +239,29 @@ private MarshallingInfo GetMarshallingInfo(
 
             // If we aren't overriding the marshalling at usage time,
             // then fall back to the information on the element type itself.
-            foreach (AttributeData typeAttribute in type.GetAttributes())
-            {
-                if (GetMarshallingInfoForAttribute(typeAttribute, type, indirectionDepth, useSiteAttributes, GetMarshallingInfo) is MarshallingInfo marshallingInfo)
-                {
-                    return marshallingInfo;
-                }
-            }
+            if (GetMarshallingInfoForAttributes(type.GetAttributes().AsSpan(), type, indirectionDepth, useSiteAttributes, GetMarshallingInfo) is MarshallingInfo info)
+                return info;
 
             // If the type doesn't have custom attributes that dictate marshalling,
             // then consider the type itself.
             return GetMarshallingInfoForType(type, indirectionDepth, useSiteAttributes, GetMarshallingInfo) ?? NoMarshallingInfo.Instance;
         }
 
         private MarshallingInfo? GetMarshallingInfoForAttribute(AttributeData attribute, ITypeSymbol type, int indirectionDepth, UseSiteAttributeProvider useSiteAttributes, GetMarshallingInfoCallback marshallingInfoCallback)
+        {
+            return GetMarshallingInfoForAttributes(new AttributeData[] { attribute }.AsSpan(), type, indirectionDepth, useSiteAttributes, marshallingInfoCallback);
+        }
+
+        private MarshallingInfo? GetMarshallingInfoForAttributes(ReadOnlySpan<AttributeData> attrs, ITypeSymbol type, int indirectionDepth, UseSiteAttributeProvider useSiteAttributes, GetMarshallingInfoCallback marshallingInfoCallback)
         {
             foreach (var parser in _marshallingAttributeParsers)
             {
-                // Automatically ignore invalid attributes.
-                // The compiler will already error on them.
-                if (attribute.AttributeConstructor is not null && parser.CanParseAttributeType(attribute.AttributeClass))
+                foreach (var attr in attrs)
                 {
-                    return parser.ParseAttribute(attribute, type, indirectionDepth, useSiteAttributes, marshallingInfoCallback);
+                    if (attr.AttributeConstructor is not null && parser.CanParseAttributeType(attr.AttributeClass))
+                    {
+                        return parser.ParseAttribute(attr, type, indirectionDepth, useSiteAttributes, marshallingInfoCallback);
+                    }
                 }
             }
             return null;

src/libraries/System.Runtime.InteropServices/tests/ComInterfaceGenerator.Tests/NativeMarshallingAttributeTests.cs

@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.Marshalling;
+using SharedTypes.ComInterfaces;
+using Xunit;
+
+namespace ComInterfaceGenerator.Tests
+{
+    public unsafe partial class NativeMarshallingAttributeTests
+    {
+        [LibraryImport(NativeExportsNE.NativeExportsNE_Binary, EntryPoint = "new_unique_marshalling")]
+        internal static partial IUniqueMarshalling NewUniqueMarshalling();
+
+        [Fact]
+        public void MethodReturningComInterfaceReturnsUniqueInstance()
+        {
+            // When a COM interface method returns the same interface type,
+            // it should return a new managed instance, not the cached one
+            var obj = NewUniqueMarshalling();
+            obj.SetValue(42);
+
+            var returnedObj = obj.GetThis();
+
+            // Should be a different managed object
+            Assert.NotSame(obj, returnedObj);
+
+            // But should refer to the same underlying COM object
+            Assert.Equal(42, returnedObj.GetValue());
+
+            // Modifying through one should affect the other
+            returnedObj.SetValue(100);
+            Assert.Equal(100, obj.GetValue());
+        }
+    }
+}

src/libraries/System.Runtime.InteropServices/tests/ComInterfaceGenerator.Unit.Tests/CodeSnippets.cs

@@ -751,5 +751,21 @@ public Bidirectional(IComInterfaceAttributeProvider attributeProvider)
 
             public IComInterfaceAttributeProvider AttributeProvider { get; }
         }
+
+        public string ComInterfaceWithNativeMarshalling => $$"""
+            using System;
+            using System.Runtime.CompilerServices;
+            using System.Runtime.InteropServices;
+            using System.Runtime.InteropServices.Marshalling;
+
+            [assembly:DisableRuntimeMarshalling]
+
+            {{GeneratedComInterface()}}
+            [NativeMarshalling(typeof(UniqueComInterfaceMarshaller<IFoo>))]
+            partial interface IFoo
+            {
+                void DoWorkTogether(IFoo foo);
+            }
+            """;
     }
 }

src/libraries/System.Runtime.InteropServices/tests/ComInterfaceGenerator.Unit.Tests/Compiles.cs

@@ -349,6 +349,7 @@ public static IEnumerable<object[]> ComInterfaceSnippetsToCompile()
             yield return new object[] { ID(), codeSnippets.ForwarderWithPreserveSigAndRefKind("ref readonly") };
             yield return new object[] { ID(), codeSnippets.ForwarderWithPreserveSigAndRefKind("in") };
             yield return new object[] { ID(), codeSnippets.ForwarderWithPreserveSigAndRefKind("out") };
+            yield return new object[] { ID(), codeSnippets.ComInterfaceWithNativeMarshalling };
         }
 
         public static IEnumerable<object[]> ManagedToUnmanagedComInterfaceSnippetsToCompile()

src/libraries/System.Runtime.InteropServices/tests/Common/ComInterfaces/IUniqueMarshalling.cs

@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.Marshalling;
+
+namespace SharedTypes.ComInterfaces
+{
+    [GeneratedComInterface]
+    [Guid(IID)]
+    [NativeMarshalling(typeof(UniqueComInterfaceMarshaller<IUniqueMarshalling>))]
+    internal partial interface IUniqueMarshalling
+    {
+        int GetValue();
+        void SetValue(int x);
+        IUniqueMarshalling GetThis();
+
+        public const string IID = "E11D5F3E-DD57-4E7E-A78C-F5F8B8E0A1F4";
+    }
+
+    [GeneratedComClass]
+    internal partial class UniqueMarshalling : IUniqueMarshalling
+    {
+        int _data = 0;
+        public int GetValue() => _data;
+        public void SetValue(int x) => _data = x;
+        public IUniqueMarshalling GetThis() => this;
+    }
+}

src/libraries/System.Runtime.InteropServices/tests/LibraryImportGenerator.Tests/LibraryImportGenerator.Tests.csproj

@@ -14,6 +14,8 @@
   <ItemGroup>
     <Compile Include="$(CommonPath)DisableRuntimeMarshalling.cs"
              Link="Common\DisableRuntimeMarshalling.cs" />
+    <Compile Include="..\Common\ComInterfaces\IUniqueMarshalling.cs"
+             Link="ComInterfaces\IUniqueMarshalling.cs" />
   </ItemGroup>
 
   <ItemGroup>

src/libraries/System.Runtime.InteropServices/tests/LibraryImportGenerator.Tests/NativeMarshallingAttributeTests.cs

@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.Marshalling;
+using SharedTypes.ComInterfaces;
+using Xunit;
+
+namespace LibraryImportGenerator.IntegrationTests
+{
+    partial class NativeExportsNE
+    {
+        [LibraryImport(NativeExportsNE_Binary, EntryPoint = "new_unique_marshalling")]
+        internal static partial IUniqueMarshalling GetUniqueMarshalling();
+    }
+
+    public class NativeMarshallingAttributeTests
+    {
+        [Fact]
+        public void GetSameComInterfaceTwiceReturnsUniqueInstances()
+        {
+            // When using NativeMarshalling with UniqueComInterfaceMarshaller,
+            // calling GetUniqueMarshalling() twice returns different managed instances for the same COM object
+            var obj1 = NativeExportsNE.GetUniqueMarshalling();
+            var obj2 = NativeExportsNE.GetUniqueMarshalling();
+
+            Assert.NotSame(obj1, obj2);
+
+            // Both refer to the same underlying COM object (same cached pointer)
+            obj1.SetValue(42);
+            Assert.Equal(42, obj2.GetValue());
+
+            // Modifying through one should affect the other
+            obj2.SetValue(100);
+            Assert.Equal(100, obj1.GetValue());
+        }
+    }
+}

src/libraries/System.Runtime.InteropServices/tests/LibraryImportGenerator.UnitTests/CodeSnippets.cs

@@ -1526,5 +1526,25 @@ public void Free() { }
                 }
             }
             """;
+
+        public static string ComInterfaceWithNativeMarshallingInLibraryImport => """
+            using System.Runtime.InteropServices;
+            using System.Runtime.InteropServices.Marshalling;
+
+            [GeneratedComInterface]
+            [Guid("0E7204B5-4B61-4E06-B872-82BA652F2ECA")]
+            [NativeMarshalling(typeof(UniqueComInterfaceMarshaller<IFoo>))]
+            partial interface IFoo
+            {
+                void DoWork();
+            }
+
+            static partial class PInvokes
+            {
+                [LibraryImport("lib")]
+                [return: MarshalAs(UnmanagedType.I1)]
+                public static partial bool TryGetFoo(out IFoo foo);
+            }
+            """;
     }
 }

src/libraries/System.Runtime.InteropServices/tests/LibraryImportGenerator.UnitTests/Compiles.cs

@@ -255,6 +255,7 @@ public static IEnumerable<object[]> CodeSnippetsToCompile()
 
             // Type-level interop generator trigger attributes
             yield return new[] { ID(), CodeSnippets.GeneratedComInterface };
+            yield return new[] { ID(), CodeSnippets.ComInterfaceWithNativeMarshallingInLibraryImport };
 
             // Parameter modifiers
             yield return new[] { ID(), CodeSnippets.SingleParameterWithModifier("int", "scoped ref") };

src/libraries/System.Runtime.InteropServices/tests/TestAssets/NativeExports/ComInterfaceGenerator/UniqueMarshalling.cs

@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.Marshalling;
+using SharedTypes.ComInterfaces;
+
+namespace NativeExports.ComInterfaceGenerator
+{
+    public static unsafe class UniqueMarshalling
+    {
+        private static void* s_cachedPtr = null;
+
+        // Call from another assembly to get a ptr to make an RCW
+        [UnmanagedCallersOnly(EntryPoint = "new_unique_marshalling")]
+        public static void* CreateComObject()
+        {
+            if (s_cachedPtr == null)
+            {
+                StrategyBasedComWrappers wrappers = new();
+                var myObject = new SharedTypes.ComInterfaces.UniqueMarshalling();
+                nint ptr = wrappers.GetOrCreateComInterfaceForObject(myObject, CreateComInterfaceFlags.None);
+                s_cachedPtr = (void*)ptr;
+            }
+
+            return s_cachedPtr;
+        }
+    }
+}