Translate VARIANT to ComVariant when using COM source generators (#1554)

Author: jevansaks

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

@@ -8,7 +8,10 @@ public partial class Generator
     /// <inheritdoc/>
     public void GenerateAllConstants(CancellationToken cancellationToken)
     {
-        foreach (FieldDefinitionHandle fieldDefHandle in this.MetadataIndex.Apis.SelectMany(api => this.Reader.GetTypeDefinition(api).GetFields()))
+        var fields = this.MetadataIndex.Apis.SelectMany(api => this.Reader.GetTypeDefinition(api).GetFields());
+        var sortedFields = fields.OrderBy(fieldDefHandle => this.Reader.GetString(this.Reader.GetFieldDefinition(fieldDefHandle).Name));
+
+        foreach (FieldDefinitionHandle fieldDefHandle in sortedFields)
         {
             cancellationToken.ThrowIfCancellationRequested();
 

src/Microsoft.Windows.CsWin32/Generator.cs

@@ -569,7 +569,7 @@ public void GenerateAllMacros(CancellationToken cancellationToken)
             return;
         }
 
-        foreach (KeyValuePair<string, MethodDeclarationSyntax> macro in Win32SdkMacros)
+        foreach (KeyValuePair<string, MethodDeclarationSyntax> macro in Win32SdkMacros.OrderBy(x => x.Key))
         {
             cancellationToken.ThrowIfCancellationRequested();
 

src/Microsoft.Windows.CsWin32/HandleTypeHandleInfo.cs

@@ -159,7 +159,7 @@ internal override TypeSyntaxAndMarshaling ToTypeSyntax(TypeSyntaxSettings inputs
                 return new TypeSyntaxAndMarshaling(IdentifierName(specialName));
             }
         }
-        else if (useComSourceGenerators && !inputs.AllowMarshaling && (simpleName is "VARIANT" or "VARIANT_unmanaged") && this.Generator.CanUseComVariant)
+        else if (useComSourceGenerators && (simpleName is "VARIANT" or "VARIANT_unmanaged") && this.Generator.CanUseComVariant)
         {
             return new TypeSyntaxAndMarshaling(QualifiedName(ParseName("global::System.Runtime.InteropServices.Marshalling"), IdentifierName("ComVariant")));
         }

test/CsWin32Generator.Tests/CsWin32GeneratorTests.cs

@@ -66,8 +66,8 @@ public async Task TestNativeMethods()
     [Fact]
     public async Task CheckITypeCompIsUnmanaged()
     {
-        // Request DebugPropertyInfo and we should see ITypeComp_unmanaged get generated because it has an embedded managed field
-        this.nativeMethods.Add("DebugPropertyInfo");
+        // Request BINDPTR and we should see ITypeComp_unmanaged get generated because it has an embedded managed field
+        this.nativeMethods.Add("BINDPTR");
         await this.InvokeGeneratorAndCompileFromFact();
 
         var iface = this.FindGeneratedType("ITypeComp_unmanaged");
@@ -565,4 +565,20 @@ public async Task CrossWinMD_IInspectable(
         this.nativeMethods.Add("ITestDerivedFromInspectable");
         await this.InvokeGeneratorAndCompile($"{nameof(this.CrossWinMD_IInspectable)}_{tfm}_{allowMarshaling}_{pinvokeClassName ?? "null"}");
     }
+
+    [Fact]
+    public async Task TestComVariantReturnValue()
+    {
+        // IUIAutomationElement has methods that return VARIANT, they should be translated to ComVariant
+        this.nativeMethods.Add("IUIAutomationElement");
+        await this.InvokeGeneratorAndCompileFromFact();
+
+        var iface = this.FindGeneratedType("IUIAutomationElement");
+        Assert.NotEmpty(iface);
+
+        // And when generating IDispatch explicitly it should have "real" methods on it.
+        var methods = iface.SelectMany(t => t.DescendantNodes().OfType<MethodDeclarationSyntax>());
+        var method = Assert.Single(methods, m => m.Identifier.Text == "GetCachedPropertyValue");
+        Assert.Contains("ComVariant", method.ReturnType.ToString());
+    }
 }