System.Runtime.Serialization.Formatters.Tests.FormatterServicesTests.GetUninitializedObject_COMObject_ThrowsNotSupportedException fails with Mono

[ViktorHofer]

Configuration: net5.0-Windows_NT-Debug-x64-Mono_release-Windows.10.Amd64.Server19H1.ES.Open

The test wasn't running before because it was excluded via TargetsWindows even though the test project is runtime agnostic.

runtime/src/libraries/System.Runtime.Serialization.Formatters/tests/System.Runtime.Serialization.Formatters.Tests.csproj

Line 15 in 632cdca

<Compile Include="FormatterServicesTests.Windows.cs" Condition="'$(TargetsWindows)' == 'true'" />

This was fixed with #35606 and started failing for Mono.

System.Runtime.Serialization.Formatters.Tests.FormatterServicesTests.GetUninitializedObject_COMObject_ThrowsNotSupportedException [FAIL]
        Assert.True() Failure
        Expected: True
        Actual:   False
        Stack Trace:
          C:\git\runtime4\src\libraries\System.Runtime.Serialization.Formatters\tests\FormatterServicesTests.Windows.cs(17,0): at System.Runtime.Serialization.Formatters.Tests.FormatterServicesTests.GetUninitializedObject_COMObject_ThrowsNotSupportedException()
          C:\git\runtime4\src\mono\netcore\System.Private.CoreLib\src\System\Reflection\RuntimeMethodInfo.cs(384,0): at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

cc @akoeplinger @lateralusX

[Dotnet-GitSync-Bot]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[akoeplinger]

@lateralusX does this seem like something that should work on netcore-mono on Windows?

[lateralusX]

@akoeplinger

So we have disabled COM support on netcore (all platforms), this is from winconfig.h

#ifndef DISABLE_COM
#define DISABLE_COM 1
#endif

and the will result in:

#ifdef DISABLE_COM
#define mono_class_is_com_object(klass) (FALSE)
#else
#define mono_class_is_com_object(klass) (m_class_is_com_object (klass))
#endif

so IsCOMObject will always return FALSE on netcore mono runtime.

Since this is a Windows only test, it won't show up on other platforms, but the same implementation should apply.

We could include some more logic where we could make IsCOMObject working for just COMObject type and make sure the rest of this test pass as well (maybe Windows only). I did similar things to make sure "minimal" COM works on Windows (basically IUnknown) even when DISABLE_COM has been defined, we could include some more needed things for this scenario to pass even when DISABLE_COM has been defined. So questions is if its worth doing that change for combability reasons of Type.IsCOMObject on Windows only?

[marek-safar]

The test will need adjustment for IsComSupported or something like that

[akoeplinger]

@marek-safar do you think we should support COM on Mono on Windows?

[marek-safar]

@akoeplinger I'm not aware of any ask to support COM with MonoVM

[HongGit]

@Benjie-Liu can you please work on this test issue?

[HongGit]

@ViktorHofer is this still an issue for you?

[ViktorHofer]

Has something changed since I filed the issue? I don't see any failures in the CI logs for the last 7 days but that doesn't mean that this isn't happening anymore.