Conflict in publish between file from Microsoft.NET.Build.Extensions and NuGet package

[dsplaisted]

With the following project:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net461</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore" Version="2.1.4" />
    <PackageReference Include="System.Runtime.InteropServices.RuntimeInformation" Version="4.3.0" />
  </ItemGroup>
</Project>

• Make sure to delete the output folder
• Publish the project and generate a .binlog (dotnet publish -bl)
• Open .binlog in MSBuild structured log viewer

Expected: No DoubleWrites reported

Actual: DoubleWrites reported for System.Runtime.InteropServices.RuntimeInformation.dll

The file is being copied to the publish folder from the following two locations:

• C:\Program Files\dotnet\sdk\NuGetFallbackFolder\system.runtime.interopservices.runtimeinformation\4.3.0\lib\net45\System.Runtime.InteropServices.RuntimeInformation.dll
• C:\Program Files\dotnet\sdk\3.1.100-preview3-014645\Microsoft\Microsoft.NET.Build.Extensions\net461\lib\System.Runtime.InteropServices.RuntimeInformation.dll

On publishing the second time, the DoubleWrite will likely not be reported, as the output will be considered up to date in the _CopyResolvedFilesToPublishPreserveNewest target.

I am not sure exactly what determines which of the files wins. However, if the wrong file is copied (and we have a customer report where this happened), then the app will fail at runtime.

[dsplaisted]

Possibly related: #10850

[sfoslund]

Fixed in .NET 6 with #14020