RequestDelegateGenerator compiler version mismatch

[mthalman]

  CSC : error CS9057: Analyzer assembly '/__w/_temp/dotnet-sources/src/aspnetcore/artifacts/bin/Microsoft.AspNetCore.Http.RequestDelegateGenerator/Release/netstandard2.0/Microsoft.AspNetCore.Http.RequestDelegateGenerator.dll' cannot be used because it references version '5.1.0.0' of the compiler, which is newer than the currently running version '5.0.0.0'. [/__w/_temp/dotnet-sources/src/aspnetcore/src/Identity/Core/src/Microsoft.AspNetCore.Identity.csproj]

This is the same issue that popped up in #5345. But it's only happening in the source-build-outer-loop pipeline which runs Mono legs.

VMR commits:

• working: 0d0ac120533f59dc1be83f960382ce1856c59485
• failing: 24f2cb8ece4b8f92df76dbaee7cdabc969a1bbf5

Failing build (internal link)

[mthalman]

@wtgodbe - Any ideas on this?

[mthalman]

Ok, now this is showing up for the rest of the source build legs. This is not a Mono-specific issue. It's a general source-build issue.

Failing build (internal link)

[mthalman]

I think dotnet/dotnet#2668 is likely the cause of this. @jjonescz - PTAL

[jjonescz]

I think dotnet/dotnet#2668 is likely the cause of this. @jjonescz - PTAL

That PR is only flowing roslyn main to VMR, the change causing this is likely the version bump to 5.1 in dotnet/roslyn@2fb0b03. But that's a standard version bump we do during snap.

From my investigation: The source build is using 10rc1 sdk which has 5.0 compiler. The aspnetcore repo builds the RequestDelegateGenerator against 5.1.0 compiler (the current version in the VMR, I assume) and then that built generator is used in subsequent builds, leading to the mismatch error. I'm not sure how to solve this, but ideally the build itself would use 5.1 version of the compiler. Also I don't know how this could have ever worked, this looks like a standard situation to me.

[mthalman]

Ok, I get what's happening. This wasn't caught by the PR build because we have a workaround related to CI builds which masked this issue: https://github.com/dotnet/dotnet/blob/afabede14c25760c8f77a36e872dcfbd3daca5d2/repo-projects/aspnetcore.proj#L72-L85. I'll work on a fix.