Fix custom marshaller namespaces for root metadata types

src/Microsoft.Windows.CsWin32/Generator.CustomMarshaller.cs

@@ -23,7 +23,7 @@ internal string RequestCustomEnumMarshaller(string qualifiedEnumTypeName, Unmana
         }
 
         // Custom marshallers should go in a InteropServices sub-namespace.
-        shortNamespace += ".InteropServices";
+        shortNamespace = shortNamespace.Length > 0 ? $"{shortNamespace}.InteropServices" : "InteropServices";
 
         string customTypeMarshallerName = $"{enumTypeName}To{unmanagedType}Marshaller";
 
@@ -115,7 +115,7 @@ internal string RequestCustomTypeDefMarshaller(string fullyQualifiedTypeName, Ty
         }
 
         // Custom marshallers should go in a InteropServices sub-namespace.
-        shortNamespace += ".InteropServices";
+        shortNamespace = shortNamespace.Length > 0 ? $"{shortNamespace}.InteropServices" : "InteropServices";
 
         string customTypeMarshallerName = $"{typeDefName}Marshaller";
 

test/CsWin32Generator.Tests/CsWin32GeneratorTests.cs

@@ -691,6 +691,64 @@ public async Task CrossWinMD_NTSTATUSSafeHandleConstant()
         Assert.Contains(this.FindGeneratedType("RtlUnsubscribeWnfStateChangeNotificationSafeHandle"), static type => type is ClassDeclarationSyntax);
     }
 
+    /// <summary>
+    /// Verifies native typedef marshaller namespaces through build-task generation and compilation.
+    /// </summary>
+    /// <param name="nestedNamespace">Whether the typedef is in a child of the common namespace.</param>
+    /// <param name="tfm">The target framework of the generated projection.</param>
+    [Theory, CombinatorialData]
+    public async Task NativeTypedefMarshallerNamespace(
+        bool nestedNamespace,
+        [CombinatorialValues("net8.0", "net9.0", "net10.0")] string tfm)
+    {
+        this.compilation = this.starterCompilations[tfm];
+        this.parseOptions = this.parseOptions.WithLanguageVersion(GetLanguageVersionForTfm(tfm)!.Value);
+        this.tfm = tfm;
+        this.win32winmdPaths = [FlatNamespaceMetadataPath];
+        string typeName = nestedNamespace ? "NESTED_HANDLE" : "TEST_HANDLE";
+        string typeNamespace = nestedNamespace ? "FlatNamespace.Nested" : "FlatNamespace";
+        string marshallerName = $"{typeNamespace}.InteropServices.{typeName}Marshaller";
+        this.nativeMethods.Add(nestedNamespace ? "UseNestedHandle" : "UseRootHandle");
+
+        await this.InvokeGeneratorAndCompile($"{nameof(this.NativeTypedefMarshallerNamespace)}_{nestedNamespace}_{tfm}");
+
+        StructDeclarationSyntax typedef = Assert.Single(this.FindGeneratedType(typeName).OfType<StructDeclarationSyntax>());
+        AttributeSyntax attribute = Assert.Single(FindAttribute(typedef.AttributeLists, "NativeMarshalling"));
+        TypeOfExpressionSyntax marshallerType = Assert.IsType<TypeOfExpressionSyntax>(Assert.Single(attribute.ArgumentList!.Arguments).Expression);
+        Assert.Equal($"global::{marshallerName}", marshallerType.Type.ToString());
+        Assert.NotNull(this.compilation.GetTypeByMetadataName(marshallerName));
+    }
+
+    /// <summary>
+    /// Verifies associated enum marshaller namespaces through build-task generation and compilation.
+    /// </summary>
+    /// <param name="nestedNamespace">Whether the enum is in a child of the common namespace.</param>
+    /// <param name="tfm">The target framework of the generated projection.</param>
+    [Theory, CombinatorialData]
+    public async Task AssociatedEnumMarshallerNamespace(
+        bool nestedNamespace,
+        [CombinatorialValues("net8.0", "net9.0", "net10.0")] string tfm)
+    {
+        this.compilation = this.starterCompilations[tfm];
+        this.parseOptions = this.parseOptions.WithLanguageVersion(GetLanguageVersionForTfm(tfm)!.Value);
+        this.tfm = tfm;
+        this.win32winmdPaths = [FlatNamespaceMetadataPath];
+        string typeName = nestedNamespace ? "NESTED_ENUM" : "TEST_ENUM";
+        string typeNamespace = nestedNamespace ? "FlatNamespace.Nested" : "FlatNamespace";
+        string marshallerName = $"{typeNamespace}.InteropServices.{typeName}ToU4Marshaller";
+        string apiName = nestedNamespace ? "UseNestedEnum" : "UseRootEnum";
+        this.nativeMethods.Add(apiName);
+
+        await this.InvokeGeneratorAndCompile($"{nameof(this.AssociatedEnumMarshallerNamespace)}_{nestedNamespace}_{tfm}");
+
+        MethodDeclarationSyntax method = Assert.Single(this.FindGeneratedMethod(apiName), m => FindAttribute(m.AttributeLists, "LibraryImport").Any());
+        ParameterSyntax parameter = Assert.Single(method.ParameterList.Parameters);
+        AttributeSyntax attribute = Assert.Single(FindAttribute(parameter.AttributeLists, "global::System.Runtime.InteropServices.Marshalling.MarshalUsing"));
+        TypeOfExpressionSyntax marshallerType = Assert.IsType<TypeOfExpressionSyntax>(Assert.Single(attribute.ArgumentList!.Arguments).Expression);
+        Assert.Equal($"global::{marshallerName}", marshallerType.Type.ToString());
+        Assert.NotNull(this.compilation.GetTypeByMetadataName(marshallerName));
+    }
+
     [Fact]
     public async Task TestComVariantReturnValue()
     {

test/Microsoft.Windows.CsWin32.Tests/ExternalMetadata/FlatNamespace.il

@@ -0,0 +1,71 @@
+// Source for FlatNamespace.winmd.
+// Root and nested native typedefs and associated enums exercise custom marshaller namespaces.
+// Regenerate with: ilasm FlatNamespace.il /dll /output=FlatNamespace.winmd
+
+.assembly extern mscorlib { .publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) .ver 4:0:0:0 }
+.assembly extern netstandard { .publickeytoken = (CC 7B 13 FF CD 2D DD 51 ) .ver 2:1:0:0 }
+.assembly extern Windows.Win32.winmd { .ver 0:0:0:0 }
+.assembly FlatNamespace { .ver 1:0:0:0 }
+.module FlatNamespace.winmd
+.module extern example.dll
+.corflags 0x00000001
+
+.class public sequential ansi sealed beforefieldinit FlatNamespace.TEST_HANDLE
+       extends [netstandard]System.ValueType
+{
+  .custom instance void [Windows.Win32.winmd]Windows.Win32.Foundation.Metadata.NativeTypedefAttribute::.ctor() = ( 01 00 00 00 )
+  .field public void* Value
+}
+
+.class public auto ansi sealed FlatNamespace.TEST_ENUM
+       extends [netstandard]System.Enum
+{
+  .field public specialname rtspecialname int32 value__
+  .field public static literal valuetype FlatNamespace.TEST_ENUM TestValue = int32(1)
+}
+
+.class public abstract auto autochar sealed beforefieldinit FlatNamespace.Apis
+       extends [netstandard]System.Object
+{
+  .method public hidebysig static pinvokeimpl("example.dll" nomangle winapi)
+          void UseRootHandle([in] valuetype FlatNamespace.TEST_HANDLE handle) cil managed
+  {
+  }
+
+  .method public hidebysig static pinvokeimpl("example.dll" nomangle winapi)
+          void UseRootEnum([in] uint32 enumValue) cil managed
+  {
+    .param [1]
+    .custom instance void [Windows.Win32.winmd]Windows.Win32.Foundation.Metadata.AssociatedEnumAttribute::.ctor(string) = ( 01 00 09 54 45 53 54 5F 45 4E 55 4D 00 00 )
+  }
+}
+
+.class public sequential ansi sealed beforefieldinit FlatNamespace.Nested.NESTED_HANDLE
+       extends [netstandard]System.ValueType
+{
+  .custom instance void [Windows.Win32.winmd]Windows.Win32.Foundation.Metadata.NativeTypedefAttribute::.ctor() = ( 01 00 00 00 )
+  .field public void* Value
+}
+
+.class public auto ansi sealed FlatNamespace.Nested.NESTED_ENUM
+       extends [netstandard]System.Enum
+{
+  .field public specialname rtspecialname int32 value__
+  .field public static literal valuetype FlatNamespace.Nested.NESTED_ENUM TestValue = int32(1)
+}
+
+.class public abstract auto autochar sealed beforefieldinit FlatNamespace.Nested.Apis
+       extends [netstandard]System.Object
+{
+  .method public hidebysig static pinvokeimpl("example.dll" nomangle winapi)
+          void UseNestedHandle([in] valuetype FlatNamespace.Nested.NESTED_HANDLE handle) cil managed
+  {
+  }
+
+  .method public hidebysig static pinvokeimpl("example.dll" nomangle winapi)
+          void UseNestedEnum([in] uint32 enumValue) cil managed
+  {
+    .param [1]
+    .custom instance void [Windows.Win32.winmd]Windows.Win32.Foundation.Metadata.AssociatedEnumAttribute::.ctor(string) = ( 01 00 0B 4E 45 53 54 45 44 5F 45 4E 55 4D 00 00 )
+  }
+}

test/Microsoft.Windows.CsWin32.Tests/ExternalMetadata/NOTICE.md

@@ -5,4 +5,5 @@ Metadata | Source
 ServiceFabric.winmd | [youyuanwu/fabric-metadata](https://github.com/youyuanwu/fabric-metadata/raw/a1bcca6ad6f6a772c9e5ff4bdba80ae5e5f24cfc/.windows/winmd/ServiceFabric.winmd)
 CustomIInspectable.winmd | Generated using WinMDGenerator toolchain. Project in the subdirectory [CustomIInspectable](../../CustomIInspectable) with build instructions in [readme.md](../../CustomIInspectable/readme.md).
 WnfWithoutStatusSuccess.winmd | Authored fixture for issue #1677 regression coverage. Its source is checked in as [WnfWithoutStatusSuccess.il](WnfWithoutStatusSuccess.il). We keep this one as IL because that is much easier to maintain than reproducing the full end-to-end WinmdGenerator workflow for a focused test asset.
-SelfContained.winmd | Authored fixture reproducing the OSClient single-`Generator` build configuration (a non-`Windows.Win32` metadata assembly with the Windows.Win32 projection provided by a reference), where special string typedefs (`PCWSTR`) must be referenced under `Windows.Win32.Foundation`. Its source is checked in as [SelfContained.il](SelfContained.il). Kept as IL for the same reason as WnfWithoutStatusSuccess.winmd.
+SelfContained.winmd | Authored fixture reproducing the OSClient single-`Generator` build configuration (a non-`Windows.Win32` metadata assembly with the Windows.Win32 projection provided by a reference), where special string typedefs (`PCWSTR`) must be referenced under `Windows.Win32.Foundation`. Its source is checked in as [SelfContained.il](SelfContained.il). Kept as IL for the same reason as WnfWithoutStatusSuccess.winmd.
+FlatNamespace.winmd | Authored fixture for issue #1848 regression coverage, with native typedefs and associated enums at the common namespace root and in a nested namespace. Its source and regeneration command are checked in as [FlatNamespace.il](FlatNamespace.il).

test/Microsoft.Windows.CsWin32.Tests/GeneratorTestBase.cs

@@ -15,6 +15,7 @@ public abstract class GeneratorTestBase : IDisposable, IAsyncLifetime
     protected static readonly string ServiceFabricMetadataPath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location!)!, "ExternalMetadata", "ServiceFabric.winmd");
     protected static readonly string CustomIInspectableMetadataPath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location!)!, "ExternalMetadata", "CustomIInspectable.winmd");
     protected static readonly string WnfWithoutStatusSuccessMetadataPath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location!)!, "ExternalMetadata", "WnfWithoutStatusSuccess.winmd");
+    protected static readonly string FlatNamespaceMetadataPath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location!)!, "ExternalMetadata", "FlatNamespace.winmd");
     protected static readonly string ApiDocsPath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location!)!, "apidocs.msgpack");
 
     protected readonly ITestOutputHelper logger;