RepositoryTask's usage of IBuildEngine4.GetRegisteredTaskObject breaks under multiple AssemblyLoadContexts.

[teo-tsirpanis]

I enabled Central Package Management in my repository and put Microsoft.DotNet.ReproducibleBuilds in a GlobalPackageReference, which means that all my projects have Sourcelink enabled. Now when I build one of these projects, I get this error right here (also opened dotnet/runtime#80526 to track its unhelpfulness):

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=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.2\System.Private.CoreLib.dll'.
Type B originates from 'System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.2\System.Private.CoreLib.dll'.

This error message tells us that the two GitRepositoryies are different. My guess is that MSBuild loads the task assembly once for each project, and they get the GitRepository from a previous invocation, which resides in a different ALC and fails to cast.

The approach of caching the repository information has to be revisited. For now I will limit SourceLink to just my library projects.

[rainersigwald]

I haven't seen that error before in a RegisterTaskObject scenario. Do you by chance have a repro of this you could share?

MSBuild should cache ALCs by path to plugin assembly, so it shouldn't be the case that there are two GitRepository types. But that is definitely what the error is about, so something appears to have broken the "should".

[teo-tsirpanis]

I created a repro in the https://github.com/teo-tsirpanis/Farkle/tree/msbuild-repro branch.

To run it you have to first run build.ps1 -t PrepareMSBuildTests, and then cd tests/Farkle.Tools.MSBuild.Tests and dotnet build.

Something I thought it might be the problem is that I'm using a globalPackagesFolder in nuget.config only for this test project and not its dependencies, but all Microsoft.Build.Tasks.Git.dll used in the tasks are the same. I also ran dotnet build-server shutdown before.

[rainersigwald]

Thanks for the repro. MSBuild Team: let's prioritize investigating this, since it appears to be a failure in a using-all-the-new-cool-stuff scenario.

[tmat]

Something I thought it might be the problem is that I'm using a globalPackagesFolder in nuget.config only for this test project and not its dependencies, but all Microsoft.Build.Tasks.Git.dll used in the tasks are the same.

@teo-tsirpanis So, yes, your build is misconfigured. You're loading two copies of Source Link - one from package cache in C:\Users\teo\.nuget\packages and the other from C:\Users\teo\code\Farkle\tests\packages. Don't do that :)

[tmat]

Fixed by dotnet/sourcelink#1034

[teo-tsirpanis]

Thanks!