dotnet publish --self-contained can't handle build-time references

[jhudsoncedaron]

Describe the bug

Regression from .NET 5

dotnet publish always wants --self-contained or --no-self-contained now and blows up on Any RID references because of it.

To Reproduce

Project file fragment that breaks

  <ItemGroup>
    <ProjectReference Include="..\Cedaron.Build.CreateAssemblyInfo\Cedaron.Build.CreateAssemblyInfo.csproj" Properties="RuntimeIdentifier=">
      <Private>false</Private>
      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
      <SkipGetTargetFrameworkProperties>true</SkipGetTargetFrameworkProperties>
      <ExcludeAssets>all</ExcludeAssets>
    </ProjectReference>
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\Cedaron.Build.GenerateDataObjects\Cedaron.Build.GenerateDataObjects.csproj" Properties="RuntimeIdentifier=">
      <Private>false</Private>
      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
      <SkipGetTargetFrameworkProperties>true</SkipGetTargetFrameworkProperties>
      <ExcludeAssets>all</ExcludeAssets>
    </ProjectReference>
  </ItemGroup>

  <Target Name="PrecompileScript" BeforeTargets="BeforeCompile">
    <Exec Command="dotnet run -c $(Configuration) --no-build --project ..\Cedaron.Build.GenerateDataObjects\Cedaron.Build.GenerateDataObjects.csproj -- -r -o PodObjects.cs schema.txt GeneratePodObjects" />
  </Target>

These are a build-tool dependencies. They should not (and are not--we excluded it when we pick up from "package") be shipped; furthermore, changing to the Any RID is correct (otherwise cross compilation won't work at all), and furthermore they must not build self-contained.

I cannot omit the <ProjectReference> entries or the build becomes unstable. It is absolutely necessary that the top-level build be able to resolve dependencies once and build once; otherwise the build will crash periodically with two copies of dotnet run trying to write to the bin or obj directories at once.

Exceptions (if any)

C:\Program Files\dotnet\sdk\6.0.201\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(150,5): error NETSDK1031: It is not supported to build or publish a self-contained application without specifying a RuntimeIdentifier. You must either specify a RuntimeIdentifier or set SelfContained to false. [C:\Users\jhudson\dev\cento_forms2\src\Cedaron.Build.CreateAssemblyInfo\Cedaron.Build.CreateAssemblyInfo.csproj]
C:\Program Files\dotnet\sdk\6.0.201\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(150,5): error NETSDK1031: It is not supported to build or publish a self-contained application without specifying a RuntimeIdentifier. You must either specify a RuntimeIdentifier or set SelfContained to false. [C:\Users\jhudson\dev\cento_forms2\src\Cedaron.Build.GenerateDataObjects\Cedaron.Build.GenerateDataObjects.csproj]

Further technical details

.NET SDK (reflecting any global.json):
Version: 6.0.201
Commit: ef40e6a

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19044
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.201\

Host (useful for support):
Version: 6.0.3
Commit: c24d9a9c91

[jhudsoncedaron]

Demonstration sample
net6refchain.zip

It builds just fine but when you run dotnet publish -r win7-x64, nope!

But change everything to .net 5 and there's no problem.
net5refchain.zip

[jhudsoncedaron]

In other news, it seems the actual reproduction command has gotten lost. It is cd Exe ; dotnet publish -r win7-x64 --self-contained

[jhudsoncedaron]

So I've tried to chance this error to its source and found some stuff.

1. The test for Self Contained that raises NETSDK1179 is wrong.

    <NETSdkWarning Condition="'$(_SelfContainedWasSpecified)' != 'true' and
                   '$(_CommandLineDefinedRuntimeIdentifier)' == 'true' and
                   '$(TargetFrameworkIdentifier)' == '.NETCoreApp' and
                   $([MSBuild]::VersionGreaterThanOrEquals($(TargetFrameworkVersion), '6.0'))"
               ResourceName="SelfContainedOptionShouldBeUsedWithRuntime" />

But _SelfContainedWasSpecified is merely

    <!-- Detecting property presence is not harmful and can be done in an unconditioned way -->
    <_SelfContainedWasSpecified Condition="'$(SelfContained)' != ''">true</_SelfContainedWasSpecified>

thus causing even an explicit framework dependent project to raise 1179.

The actual error happens at

    <NETSdkError Condition="'$(SelfContained)' == 'true' and '$(RuntimeIdentifier)' == ''"
                 ResourceName="CannotHaveSelfContainedWithoutRuntimeIdentifier" />

which means that SelfContained propagated down the dependent references.