Duplicate items in _ResolvedCopyLocalPublishAssets

[sbomer]

• When ResolveCopyLocalAssets runs during self-contained publish (_UseBuildDependencyFile is false), it outputs _ResolvedCopyLocalPublishAssets.
• When _ComputeResolvedCopyLocalPublishAssets runs, it adds to _ResolvedCopyLocalPublishAssets the contents of (ReferenceCopyLocalPaths \ _ResolvedCopyLocalBuildAssets):
  

  sdk/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Publish.targets

  Lines 398 to 399 in c60af5f

  	<_ResolvedCopyLocalPublishAssets Include="@(ReferenceCopyLocalPaths)"
  	Exclude="@(_ResolvedCopyLocalBuildAssets)"

_ResolvedCopyLocalBuildAssets is empty, so it gets a duplicate copy of items in ReferenceCopyLocalPaths (which comes from RuntimePackAsset), for example System.Private.CoreLib.dll.

Before #2646, ResolvedAssembliesToPublish only had one Item for System.Private.CoreLib.dll. I noticed this while trying to update https://github.com/mono/linker/blob/master/src/ILLink.Tasks/ILLink.Tasks.targets#L451 to work with the newest SDK. _ManagedAssembliesToLink was computed from ResolvedAssembliesToPublish, but that line breaks when there are multiple files with the same Filename in the input:

C:\Users\svbomer\.nuget\packages\illink.tasks\0.1.6\build\ILLink.Tasks.targets(451,34): error MSB4094: "C:\Users\svbomer\.nuget\packages\runtime.win-x64.microsoft.netcore.app\3.0.0-preview-27324-5\runtimes\win-x64\native\System.Private.CoreLib.dll;C:\Users\svbomer\.nuget\packages\runtime.win-x64.microsoft.netcore.app\3.0.0-preview-27324-5\runtimes\win-x64\native\System.Private.CoreLib.dll" is an invalid value for the "AssemblyPath" parameter of the "CheckEmbeddedRootDescriptor" task. Multiple items cannot be passed into a parameter of type "Microsoft.Build.Framework.ITaskItem". [D:\linker\test\ILLink.Tasks.Tests\bin\debug\netcoreapp3.0\helloworld\helloworld.csproj]

#2666 may be relevant.

/cc @peterhuene @nguerrera

[peterhuene]

The simple fix would be to just filter out RuntimePackAsset when adding items from ReferenceCopyLocalPaths.

Unfortunately it also seems that the runtime pack changes also introduced package references that are publish=false by default (i.e. the implicitly defined packages that are from the runtime packs which have their assets available in the RuntimePackAsset items).

As the set of packages now differs from the build, this causes the publish targets to fallback to resolving (non-platform) assets and generating a different deps file, which you can see just by diffing the deps file from build vs. publish; the former has entries for the packages excluded from publish and the latter does not.

This logic is getting difficult to reason because data is coming from many different places into the _ResolvedCopyLocalPublishAssets items. I'm working on a better solution than simply filtering out RuntimePackAsset from ReferenceCopyLocalPaths when adding to _ResolvedCopyLocalPublishAssets.