MSBuild inconsistent file path to the same Task assembly load casing cast error

[wli3]

Steps to reproduce

Failed to build https://github.com/dotnet-maestro-bot/cli/tree/merge/release/3.1.1xx-to-release/3.1.2xx due to error:

C:\work\cli\src\Microsoft.DotNet.MSBuildSdkResolver\Microsoft.DotNet.MSBuildSdkResolver.csproj]
C:\work\cli\.packages\microsoft.build.tasks.git\1.0.0-beta2-19367-01\buildCrossTargeting\Microsoft.Build.Tasks.Git.targets(24,5): error MSB4018: 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=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\work\cli\.dotnet\shared\Microsoft.NETCore.App\3.1.2\System.Private.CoreLib.dll'. Type B originates from 'System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' in the context 'Default' at location 'C:\work\cli\.dotnet\shared\Microsoft.NETCore.App\3.1.2\System.Private.CoreLib.dll'. [C:\work\cli\src\Microsoft.DotNet.MSBuildSdkResolver\Microsoft.DotNet.MSBuildSdkResolver.csproj]
C:\work\cli\.packages\microsoft.build.tasks.git\1.0.0-beta2-19367-01\buildCrossTargeting\Microsoft.Build.Tasks.Git.targets(24,5): error MSB4018:    at Microsoft.Build.Tasks.Git.RepositoryTask.TryGetCachedRepositoryInstance(String cacheKey, Boolean requireCached, GitRepository& repository) in /_/src/Microsoft.Build.Tasks.Git/RepositoryTask.cs:line 135 [C:\work\cli\src\Microsoft.DotNet.MSBuildSdkResolver\Microsoft.DotNet.MSBuildSdkResolver.csproj]

The same assembly with different path is loaded

It is caused by path in https://github.com/microsoft/msbuild/blob/86d9494e446de002ea6a4f08d6fbd111b1041059/src/Shared/CoreCLRAssemblyLoader.cs#L32 is not normalized.

[rainersigwald]

The task in question here uses RegisterTaskObject/GetRegisteredTaskObject to store and retrieve an object across invocations.

https://github.com/dotnet/sourcelink/blob/39c946a79b0daca4e47ec6d23554fea69f33253d/src/Microsoft.Build.Tasks.Git/RepositoryTask.cs#L153-L160

This retrieves an object from an ALC loaded through one path (build/../foo.dll) into an ALC loaded through another (buildCrossTargeting/../foo.dll), which causes the problems.

[dsplaisted]

@rainersigwald So do you know what we need to do to fix this? Do keys for task objects need to now be aware of the ALC?

[rainersigwald]

There's an easy fix here for task objects used within a single assembly: normalize the path to that assembly. There's still a conceivable hole if the register/retrieve goes across assemblies (#5084), but I don't know if that actually happens. Since it might I think we should build an escape hatch back to legacy one-ALC behavior (#5086).

[rainersigwald]

For posterity, this reproed at the commit here: dotnet/cli@cd47882

(thanks @sfoslund!)