Only target NetCurrent for source build

[mthalman]

The NetCurrent property is the only value that should be targeted in the context of source build. Otherwise, when NetCurrent is net10.0 and NetPrevious is net9.0, you can run into this error when building with the latest .NET 10 SDK build:

/repos/dotnet/.dotnet/sdk/10.0.100-alpha.1.24611.6/Microsoft.Common.CurrentVersion.targets(1889,5): Project '../MSBuild.BuildHost/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.csproj' targets 'net10.0'. It cannot be referenced by a project that targets '.NETCoreApp,Version=v9.0'. [/repos/dotnet/src/roslyn/src/Workspaces/Core/MSBuild/Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj]

Found as part of the work on dotnet/sdk#45435.

[ViktorHofer]

@mthalman this got fixed / worked around with 58d7d7b already.

[mthalman]

@mthalman this got fixed / worked around with 58d7d7b already.

That doesn't solve the problem. It still attempts to build Microsoft.CodeAnalysis with the net9.0 TFM in a source build configuration which leads to the following errors:

CSC error CS0006: Metadata file '/repos/dotnet/src/roslyn/artifacts/sb/package-cache/microsoft.netcore.app.ref/9.0.0/analyzers/dotnet/cs/Microsoft.Interop.ComInterfaceGenerator.dll' could not be found [/repos/dotnet/src/roslyn/src/Compilers/Core/Portable/Microsoft.CodeAnalysis.csproj]
CSC error CS0006: Metadata file '/repos/dotnet/src/roslyn/artifacts/sb/package-cache/microsoft.netcore.app.ref/9.0.0/analyzers/dotnet/cs/Microsoft.Interop.LibraryImportGenerator.dll' could not be found [/repos/dotnet/src/roslyn/src/Compilers/Core/Portable/Microsoft.CodeAnalysis.csproj]
CSC error CS0006: Metadata file '/repos/dotnet/src/roslyn/artifacts/sb/package-cache/microsoft.netcore.app.ref/9.0.0/analyzers/dotnet/cs/Microsoft.Interop.SourceGeneration.dll' could not be found [/repos/dotnet/src/roslyn/src/Compilers/Core/Portable/Microsoft.CodeAnalysis.csproj]
CSC error CS0006: Metadata file '/repos/dotnet/src/roslyn/artifacts/sb/package-cache/microsoft.netcore.app.ref/9.0.0/analyzers/dotnet/cs/System.Text.Json.SourceGeneration.dll' could not be found [/repos/dotnet/src/roslyn/src/Compilers/Core/Portable/Microsoft.CodeAnalysis.csproj]
CSC error CS0006: Metadata file '/repos/dotnet/src/roslyn/artifacts/sb/package-cache/microsoft.netcore.app.ref/9.0.0/analyzers/dotnet/cs/System.Text.RegularExpressions.Generator.dll' could not be found [/repos/dotnet/src/roslyn/src/Compilers/Core/Portable/Microsoft.CodeAnalysis.csproj]

This happens because it's loading the 9.0 targeting back from SBRP which has no analyzers. But the point is, it shouldn't be attempting to target net9.0 in full source build.

roslyn-sb-vmr-binlog.zip

[ViktorHofer]

Yes, I agree that when building roslyn from source NetPrevious shouldn't get built. We had a discussion about this in the linked PR and it sounds like others agree on this as well and we should make the change eventually. From the changes in this PR, NetPrevious still gets built. I would expect L57 and L58 to also need to change.