When using the MSBuild package with Blazor library extra content files are added to nupkg

Bug Report

When using the Microsoft.Typescript.MSBuild 4.2.1-rc to pack a Blazor Library project for nuget package, the compiled javascript files are added to the content and contentFiles folders of the nuget package, not just to staticWebAssets that Blazor build picks up.

GetTypeScriptOutputForPublishing MSBuild target seems to be the source of errors, if the content of that target is commented out, the nuget package does not have the above problem.

UPDATE

The real sideeffects of this coming to the surface when the build nuget package is consumed in another Blazor project and being built in VS 2019 16.x. As the JS files are showing up in the consuming project as project items and they should not. The worse thing is that if you put a tsconfig.json into the Logging package no matter if it is a <None.... item, that will also be packed and will cause compilation failure in the consuming project as there will be no source files to compile (that's how we started to notice this problem).

Repro

1. Clone https://github.com/BlazorExtensions/Logging
2. dotnet pack
3. Observe the contents of the nupkg file

🔎 Search Terms

msbuild, nuget, blazor

🙁 Actual behavior

See in summary above.

🙂 Expected behavior

Nuget package should not have those extra files.