Determine why analyzers are running on generated not supported assemblies auto-generated files

[stephentoub]

Our root .editorconfig lists *.notsupported.cs as being consider auto-generated, but for some reason that .editorconfig isn't being passed to csc when building those assemblies, e.g. Microsoft.Win32.Registry. As a result, analyzers are running on the auto-generated .notsupported.cs file there.

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Issue Details

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Our root .editorconfig lists *.notsupported.cs as being consider auto-generated, but for some reason that .editorconfig isn't being passed to csc when building those assemblies, e.g. Microsoft.Win32.Registry. As a result, analyzers are running on the auto-generated .notsupported.cs file there.

Author:	stephentoub
Assignees:	-
Labels:	area-Infrastructure-libraries
Milestone:	-

[ViktorHofer]

Roslyn's msbuild targets auto-discover editorconfig files based on the compile items defined: https://github.com/dotnet/roslyn/blob/3b23723934d3c7d0b3c1a0165def4a7f0e6e3a19/src/Compilers/Core/MSBuildTask/Microsoft.Managed.Core.targets#L125-L140

TFMs that are pure PNSEs don't have any compile items defined at evaluation time. The compile item that is generated by GenFacades which is called NotSupported.cs doesn't exist at evaluation time and hence the logic is skipped.

To fix this for PNSE projects (which are a dotnet/runtime only concept), we could trigger the auto-discovery based on the project file instead. That could be accomplished here: https://github.com/dotnet/arcade/blob/17d9eee32f20a6af0ebb620254a22f601d159578/src/Microsoft.DotNet.GenFacades/build/Microsoft.DotNet.GenFacades.NotSupported.targets#L20

@carlossanlop @ericstj this is another refcount on issues with our PNSE custom infrastructure (in addition to the /// xml comment source of truth issue with PNSEs).

[ViktorHofer]

Filed dotnet/roslyn#67793 as the auto-discovery doesn't work either for projects which define their compile items outside of the project file, in a Directory.Build.targets file. Adding the tracking-external-issue label.

[stephentoub]

Thanks, @ViktorHofer