ResolvePackageAssets task should log package dependency chain on each item

Originally posted by @KirillOsenkov in https://github.com/NuGet/Home/issues/10796#issue-865359017

The ResolvePackageAssets task takes in PackageReference items and produces RuntimeCopyLocalItems. It is not clear why a certain file ends up in RuntimeCopyLocalItems.

A new metadata should be logged on each file that shows the dependency chain from a root package to the package that caused this file inclusion.

This information is available in project.assets.json but is very hard to parse.

Having this metadata would significantly simplify investigations answering questions such as “why is this file being copied to output” and “which NuGet package was the root package that eventually caused this file to be included”.

Mockup:

[dsplaisted]

This doesn’t seem to me like something that we should be doing in ResolvePackageAssets. We’d need to reconstruct the package graph and walk it, which I don’t think we currently do at all. Also, there’s not necessarily just one path of dependencies, and there may be more than one root PackageReference bringing something in.

I think if you search for the asset in the Solution Explorer in Visual Studio, it may show you the dependency chain. Barring that, I think the best solution would be to have a tool that can process the assets file and produce this information.

[KirillOsenkov]

@dsplaisted @rainersigwald