[Bug] .NET API bug UWP No longer supported about docfx

[filzrev]

I've tried to use Roslyn 4.9.0-3.23612.11 (It requires .NET preview NuGet feed).
And It can be successfully running dotnet metadata command.

So this issue will be resolved when Roslyn v4.9.0 is officially released Expected on Feb '24.

[filzrev]

On my environment.
Following warning message is displayed before CS0246 errors.

warning: [Failure] Msbuild failed when processing the file 'C:\projects\Rx.NET\Source\src\System.Reactive\System.Reactive.csproj' with message: The specified language targets for uap10.0.18362 is missing. Ensure correct tooling is installed for 'uap'. Missing: 'C:\Program Files\dotnet\sdk\8.0.202\Microsoft\WindowsXaml\v17.0\Microsoft.Windows.UI.Xaml.CSharp.targets'

Above message path indicating .NET SDK version of MSBuild is selected from $(MSBuildExtensionsPath) .
It should use Visual Studio version of MSBuild host instead when generating UWP app metadata.

I've checked how Roslyn 4.9.2 or later execute analysis out-of-process. (dotnet/roslyn#70469)
But can't find ways to change behaviors.

[filzrev]

But can't find ways to change behaviors.

BuildHost process kind selection logics are hardcoded at https://github.com/dotnet/roslyn/blob/0d1f9fea04892d9e65e9a780bb773a4d5ed18f8e/src/Workspaces/Core/MSBuild/MSBuild/BuildHostProcessManager.cs#L278-L336.

So when using SDK style projects.
.NET SDK version of MSBuild seems used always.

---

As a workaround.
It can be resolved by manually importing Microsoft.Windows.UI.Xaml.CSharp.targets file when running docfx metadata command for UWP.

Steps

1. Add following lines at end of NmeaParser.csproj

  <Import Project="$(MSBuildExtensionsPath)\Microsoft\WindowsXaml\v$(VisualStudioVersion)\Microsoft.Windows.UI.Xaml.CSharp.targets"
          Condition="'$(TargetFramework)' == 'uap10.0.18362' AND '$(DocfxBuild)' == 'true'" />

2. Edit docfx.config and change settings for UWP metadata generation.

"properties": {
        "TargetFrameworks": "uap10.0.18362",
        "DocfxBuild": "true", 
        "MSBuildExtensionsPath": "C:\\Program Files\\Microsoft Visual Studio\\2022\\Preview\\MSBuild"
      },

Note: MSBuild path is depends on VS edition and installed paths.

I don't have Xamarin.Android/Xamarin.iOS build environment thought.
It'll be resolved similar changes.

[dotMorten]

I'm starting to think the reason is because it can't find Visual Studio because that code isn't included in netcoreapp targets:
https://github.com/microsoft/MSBuildLocator/blob/02c357a9554bf91db26d97c32559e03bbae41501/src/MSBuildLocator/MSBuildLocator.cs#L343-L360
Probably this issue here: microsoft/MSBuildLocator#152

[filzrev]

As described in linked-issue comment (https://github.com/microsoft/MSBuildLocator/issues/152#issuecomment-1839391035)
It' required to run MSBuild on separate process.

It might be resolved when next Roslyn version(4.9.0) released.
Because MSBuildWorkspace build behavior is changed to running out-of-proc.
https://github.com/dotnet/roslyn/issues/61454#issuecomment-1813193707

[yufeih]

I've tried to use Roslyn 4.9.0-3.23612.11 (It requires .NET preview NuGet feed). And It can be successfully running dotnet metadata command.

So this issue will be resolved when Roslyn v4.9.0 is officially released Expected on Feb '24.

Nice finding! Out of proc execution solves a whole class of problems with msbuild.

[dotMorten]

@yufeih how was this addressed? With 2.76.0 I'm not able to build UWP projects and getting this warning right before all the errors:

warning: [Failure] Msbuild failed when processing the file 'e:\GitHub\dotMorten\NmeaParser\src\NmeaParser\NmeaParser.csproj' with message: If you are building projects that require targets from full MSBuild or MSBuildFrameworkToolsPath, you need to use desktop msbuild ('msbuild.exe') instead of 'dotnet build' or 'dotnet msbuild'

[filzrev]

If you are building projects that require targets from full MSBuild or MSBuildFrameworkToolsPath, you need to use desktop msbuild ('msbuild.exe') instead of 'dotnet build' or 'dotnet msbuild'

Above message is raised by MSBuildExtras package.
It might be resolved by setting "_SdkIgnoreMSBuildCoreWarning": "true"

[dotMorten]

@filzrev Thanks I tried that both in the project and in the metadata properties, but no luck. I'm getting the same error for UWP, Xamarin.Android and Xamarin.iOS.
Setting the property does get rid of the warning, but not the error. I think all that warning was doing was warning me about what is about to happen:

warning: [Warning] Unresolved metadata reference removed from project: e:\mscorlib.dll
error: c:\myproject\obj\Release\uap10.0.18362\.NETCore,Version=v5.0.AssemblyAttributes.cs(4,20): error CS0400: The type or namespace name 'System' could not be found in the global namespace (are you missing an assembly reference?)
error: c:\myproject\obj\Release\uap10.0.18362\NmeaParser.AssemblyInfo.cs(13,12): error CS0246: The type or namespace name 'System' could not be found (are you missing a using directive or an assembly reference?)
error: c:\myproject\obj\Release\uap10.0.18362\NmeaParser.AssemblyInfo.cs(14,12): error CS0246: The type or namespace name 'System' could not be found (are you missing a using directive or an assembly reference?)

[dotMorten]

@filzrev Thanks for this, but unfortunately this isn't a good solution still because of the hardcoded paths to msbuild, and not everyone is using preview, or enterprise, professional or buildtools versions.
I haven't been able to get it to generate metadata for Xamarin.Android or Xamarin.iOS either since this change, and your solution doesn't work for that (with the import path updated for those).