Universe builds cause warning "Microsoft.Common.props cannot be imported again"

[natemcmaster]

Something is causing Microsoft.Common.props to be imported multiple times from KoreBuild.proj.

This warning is new, so something might have changed in MSBuild or Microsoft.NET.Sdk.

Example: http://aspnetci/viewLog.html?buildId=193962&buildTypeId=Lite_UniverseTest&tab=buildLog

[15:00:29]C:\BuildAgent\work\33bdfc1cae7b2a38\.dotnet\sdk\2.0.0-preview1-005418\Sdks\Microsoft.NET.Sdk\Sdk\Sdk.props(19,3): warning MSB4011: "C:\BuildAgent\work\33bdfc1cae7b2a38\.dotnet\sdk\2.0.0-preview1-005418\15.0\Microsoft.Common.props" cannot be imported again. It was already imported at "C:\BuildAgent\work\33bdfc1cae7b2a38\.dotnet\sdk\2.0.0-preview1-005418\Microsoft.Common.CurrentVersion.targets (19,3)". This is most likely a build authoring error. This subsequent import will be ignored. [C:\BuildAgent\work\33bdfc1cae7b2a38\.build\KoreBuild.proj]
[15:00:29]C:\BuildAgent\work\33bdfc1cae7b2a38\.dotnet\sdk\2.0.0-preview1-005418\Sdks\Microsoft.NET.Sdk\Sdk\Sdk.targets(40,3): warning MSB4011: "C:\BuildAgent\work\33bdfc1cae7b2a38\.dotnet\sdk\2.0.0-preview1-005418\Microsoft.Common.CurrentVersion.targets" cannot be imported again. It was already imported at "C:\BuildAgent\work\33bdfc1cae7b2a38\.dotnet\sdk\2.0.0-preview1-005418\Microsoft.Common.targets (114,3)". This is most likely a build authoring error. This subsequent import will be ignored. [C:\BuildAgent\work\33bdfc1cae7b2a38\.build\KoreBuild.proj]

[natemcmaster]

We shouldn't use Microsoft.NET.Sdk props or targets from KoreBuild. These targets may alter the default lifecycle.

The problem was introduced in aspnet/Universe@71d09dc. A better fix for the problem is to add a .props file to the PackagePublisher project that sets a variable to the location of the tool instead of relying on the "RunResolvePackageDependencies" target to read project.assets.json.

cc @pakrym @pranavkm

[pranavkm]

Could we add a ResolvePackagePath to the SDK? This way we wouldn't need to reauthor individual tools to be tasks (plus helps with things like Razor where we're trying to locate 3rd party packages).

[natemcmaster]

Re-authoring as tasks isn't necessary to resolve this. See aspnet/BuildTools#239

[pranavkm]

Couldn't we just read the graph file in a task instead? Wouldn't need to change individual tasks to support this feature.

[natemcmaster]

Just to clarify, my main concern with the import warnings is that importing everything from Microsoft.Net.Sdk/Sdk.{props, targets} may interfere with KoreBuild.

Couldn't we just read the graph file in a task instead?

We could, but I don't think we should write our own task to do this. It is possible to re-use the ResolvePackageDependencies from Microsoft.NET.Sdk without importing all of their targets to go with it.

<UsingTask TaskName="Microsoft.NET.Build.Tasks.ResolvePackageDependencies"	             
      AssemblyFile="$(MicrosoftNETBuildTasksAssembly)" />

The trick is figuring out where MicrosoftNETBuildTasksAssembly is as this comes from the targets in MIcrosoft.NET.Sdk. MSBuildSdksPath might work.