Microsoft.UI.Xaml.winmd not included in build output

[ollitanska]

Describe the bug

After upgrading to v2.6.0-prerelease.210315002 from v2.6.0-prerelease.210227001, the Microsoft.UI.Xaml.winmd is not included in the output directory anymore. Microsoft.UI.Xaml.dll and Microsoft.UI.Xaml.pri are included as expected.

This causes the following exception when starting up the application: 'System.TypeLoadException: Could not find Windows Runtime type 'Microsoft.UI.Xaml.Controls.XamlControlsResources'.

This regression seems to be caused by this commit: #4218

Steps to reproduce the bug

1. Follow the Xaml Islands guide on https://docs.microsoft.com/en-us/windows/apps/desktop/modernize/host-custom-control-with-xaml-islands
2. Install version v2.6.0-prerelease.210227001 of the package, application should start fine
3. Install version v2.6.0-prerelease.210315002 of the package, application will not start. No .winmd file and got System.TypeLoadException exception

Expected behavior
Application would startup normally, Microsoft.UI.Xaml.winmd would be included in the output directory.

Version Info

NuGet package version:
[Microsoft.UI.Xaml.v2.6.0-prerelease.210315002]

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context
WPF application that hosts a custom UWP control (which uses WinUI 2.6) via XAML Islands.

[StephenLPeters]

@ollitanska Thanks for the bug! do you have a repro app you could provide here? it would be handy in fixing this :)

[StephenLPeters]

@ranjeshj I think this is needed for 2.6 release.

[ollitanska]

@ollitanska Thanks for the bug! do you have a repro app you could provide here? it would be handy in fixing this :)

Here is a minimal repro app.

XamlIslandsSample.zip

[llongley]

Hi @ollitanska - I have a candidate fix that works on my side, but I was hoping you could test it out and see if it works for you as well before I send it out for PR. Could you put this at the very bottom of App1.csproj, just before </Project>?

  <Target Name="_AddXamlWinmdToPackageLayoutRoot" AfterTargets="BuildNativePackage">
    <ItemGroup>
      <AppxPackagePayload Include="@(XamlWinmd)">
        <TargetPath>Microsoft.UI.Xaml.winmd</TargetPath>
      </AppxPackagePayload>
    </ItemGroup>
    <Copy SourceFiles="@(XamlWinmd)" DestinationFiles="@(XamlWinmd -> '$(OutDir)\%(Filename)%(Extension)')" />
  </Target>

If this does work for you, also try it in whatever app you were using where you found this. If it works in both locations, I can get this fix in the pipeline.

[ollitanska]

Hi @ollitanska - I have a candidate fix that works on my side, but I was hoping you could test it out and see if it works for you as well before I send it out for PR. Could you put this at the very bottom of App1.csproj, just before </Project>?

  <Target Name="_AddXamlWinmdToPackageLayoutRoot" AfterTargets="BuildNativePackage">
    <ItemGroup>
      <AppxPackagePayload Include="@(XamlWinmd)">
        <TargetPath>Microsoft.UI.Xaml.winmd</TargetPath>
      </AppxPackagePayload>
    </ItemGroup>
    <Copy SourceFiles="@(XamlWinmd)" DestinationFiles="@(XamlWinmd -> '$(OutDir)\%(Filename)%(Extension)')" />
  </Target>

If this does work for you, also try it in whatever app you were using where you found this. If it works in both locations, I can get this fix in the pipeline.

Works great, both on the repro app and our real app!

Thanks for quick response!

[llongley]

Sweet, thanks for the confirmation! I'll get that out for PR.

[sylveon]

Is it possible to add an option to not copy the file still, since C++ based Xaml islands apps don't need the winmd.