Running --test against a stage2 build tries to extract Private.SourceBuilt.Artifacts

[tmds]

When our CI does a second stage build, it takes an SDK and Private.SourceBuilt.Artifacts tarball, extracts them in directories and then invokes something like:

./build.sh --with-system-libs -lttng+brotli++rapidjson++zlib+ --with-sdk /home/tester/workdir/dotnet/sdk --with-packages /home/tester/workdir/dotnet/packages --source-only /p:OfficialBuildId=20250929.15

When this command completes, the same command gets ran again with the --test argument added.

This command fails as follows:

Using custom bootstrap SDK from '/home/tester/workdir/dotnet/sdk', version '10.0.100-rtm.25479.115'
NuGet packages cache: '/home/tester/workdir/dotnet/.packages/tests/'
Found bootstrap versions: SDK 10.0.100-rtm.25479.115, Arcade 10.0.0-beta.25479.115, NoTargets 3.7.0 and Traversal 3.4.0
Shutting down MSBuild server...
MSBuild server shut down successfully.

  tar (child): /home/tester/workdir/dotnet/prereqs/packages/archive/Private.SourceBuilt.Artifacts.*.tar.gz: Cannot open: No such file or directory
  tar (child): Error is not recoverable: exiting now
  tar: Child returned status 2
  tar: Error is not recoverable: exiting now
/home/tester/workdir/dotnet/eng/init-source-only.proj(33,5): error MSB3073: The command "tar -xzf /home/tester/workdir/dotnet/prereqs/packages/archive/Private.SourceBuilt.Artifacts.*.tar.gz" exited with code 2.

I'm not sure why --test tries to extract the tarball. I expect that, like build, it should not do this when --with-packages is specified.

cc @ViktorHofer

[ViktorHofer]

Did this change recently? cc @mthalman @dotnet/source-build

[tmds]

I don't think this changed recently. From the CI it seems the behavior has been like this for all the .NET 10 stage 2 builds.

I hadn't noticed before because test failures in other test suites masked that these tests weren't actually running at all.

I assume it's an error that the command tries to extract the Private.SourceBuilt.Artifacts for this invocation.

[tmds]

This does work for .NET 9. It regressed for .NET 10 some months ago.