Bootstrap stage 2 build failure in Microsoft.Build.Tasks.Git.LocateRepository task

[mthalman]

/vmr/.dotnet/sdk/8.0.100-preview.4.23219.1/Sdks/Microsoft.Build.Tasks.Git/build/Microsoft.Build.Tasks.Git.targets(26,5): error MSB4018: The "Microsoft.Build.Tasks.Git.LocateRepository" task failed unexpectedly.
System.InvalidCastException: [A]System.Runtime.CompilerServices.StrongBox`1[Microsoft.Build.Tasks.Git.GitRepository] cannot be cast to [B]System.Runtime.CompilerServices.StrongBox`1[Microsoft.Build.Tasks.Git.GitRepository]. Type A originates from 'System.Private.CoreLib, Version=8.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location '/vmr/.dotnet/shared/Microsoft.NETCore.App/8.0.0-preview.4.23217.4/System.Private.CoreLib.dll'. Type B originates from 'System.Private.CoreLib, Version=8.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location '/vmr/.dotnet/shared/Microsoft.NETCore.App/8.0.0-preview.4.23217.4/System.Private.CoreLib.dll'.
   at Microsoft.Build.Tasks.Git.RepositoryTask.TryGetCachedRepositoryInstance(String cacheKey, Boolean requireCached, GitRepository& repository)
   at Microsoft.Build.Tasks.Git.RepositoryTask.GetOrCreateRepositoryInstance()
   at Microsoft.Build.Tasks.Git.RepositoryTask.ExecuteImpl()
   at Microsoft.Build.Tasks.Git.RepositoryTask.Execute()
   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
   at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask) [/vmr/src/source-build-reference-packages/artifacts/source-build/self/src/src/targetPacks/ILsrc/microsoft.netcore.app.ref/7.0.0/Microsoft.NETCore.App.Ref.7.0.0.csproj]

This occurs in the dependency project build of SBRP when attempting to build Microsoft.NETCore.App.Ref.7.0.0.

Build link (internal only)

[dotnet-issue-labeler]

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.

[mthalman]

This seems related to the addition of Microsoft.Build.Tasks.Git.8.0.0-beta.23210.3 to the prebuilts.

[MichaelSimons]

[Triage] The fix for dotnet/sdk#31863 should have come in this morning so this should be fixed.

[MichaelSimons]

This is still not resolved.

[MichaelSimons]

It's possible the packages from prebuilts are causing this. Removing them in dotnet/installer#16176.

[MichaelSimons]

It's possible the packages from prebuilts are causing this. Removing them in dotnet/installer#16176.

Unfortunately it didn't resolve the issue.

[mthalman]

@tmat, @ViktorHofer - Could you help in determining the cause of this failure?

For context, this is failing in the bootstrap build workflow where we source-build the https://github.com/dotnet/dotnet repo once and then use the outputted SDK as the toolset to build the source again. It fails in that second build.

I've attached the build's binlog:
sourcebuild-dependency-projects.zip

What's odd about the exception message is that it's complaining that Type A can't be cast to Type B even though it reports that Type A and B are the same type from the same assembly file. I suspect that it's possible the message is actually wrong here given that it's a generic type and the real casting issue is with the GitRepository type. It doesn't indicate anything about that type's assembly in the error.

Here's the relevant code doing the cast: https://github.com/dotnet/dotnet/blob/e2903bde31921e07bebca58f03f6b1395dd74802/src/sourcelink/src/Microsoft.Build.Tasks.Git/RepositoryTask.cs#L150

It's possible that use of an MSBuild registered task object is a factor here.

[mthalman]

I took a shot in the dark and added a call to dotnet build-server shutdown right before this line:

https://github.com/dotnet/dotnet/blob/e2903bde31921e07bebca58f03f6b1395dd74802/src/source-build-reference-packages/eng/Build.props#L181

But that made no difference.

[tmat]

Seems like a dup: dotnet/sourcelink#1007, dotnet/msbuild#8478
@rainersigwald

[mthalman]

@rainersigwald - Please work with @tmat / sourcelink folks to determine a fix or workaround for this. This is blocking the source-build release of 8.0 Preview 4.

[tmat]

As a workaround I can add try-catch around the cache lookup. It will be a potential build perf issue, but not correctness issue.

[tmat]

Here: dotnet/sourcelink#1008

[tmat]

I'm gonna close this issue as it should be addressed by the above workaround. Still keeping the msbuild issue opened to track the root cause.

[mthalman]

I'd rather keep this open until our build is actually passing.

[tmat]

@mthalman
The log #3399 (comment) shows there are two copies of Source Link assembly loaded to the build process:

Is this expected?

[mthalman]

I would think that's a possibility. It would be a scenario where a project has a compile-time dependency on Microsoft.Build.Tasks.Git and the logic of the SDK has a runtime dependency on Microsoft.Build.Tasks.Git.

[rainersigwald]

That shouldn't be a conflict; the compile-time dependency shouldn't be loaded by any part of MSBuild in a persistent way, while the SDK reference (UsingTask) would.

The log shows that the assembly is being loaded in the latter way from two different paths:

This looks like it might be fallout from the temporary situation where that task is present both in the SDK and via package--and I'd expect the long-term fix to be that the package goes away and only the SDK copy is used in sourcebuild.