multi-root workspace - Test Explorer gets stuck after 7 folders and discovery still pending

[tboddyspargo]

@eleanorjboyd - I don't know about others, but I'm still experiencing a situation where the Test Explorer gets stuck and stops enumerating discovered tests (or test discovery itself is stuck...). Some (~7) of my workspace folders populate with tests, 2 of them show errors, but the loading indicator never goes away and the rest of them (~10) never populate.

I'm on ms-python.python pre-release version 2024.23.20241219, which I think should include the fix for this issue (?). I've been able to reproduce it with every version since 2024.21.0 (including every pre-release version).

My work-around is to revert back to 2024.20.0 where the issue is not reproducible.

From the logs, it's clear that discover HAS completed for some of the missing folders, but the Test Explorer is stuck and hasn't added/rendered those nodes. Is there perhaps some disconnect between the background processes and the "listeners" for them? Do they become "misaligned" after one discovery hits an error? I'll note that, in the past, I've noticed that test discovery/run/debug has had a harder time recovering from import-time Exceptions/failures (e.g. ModuleNotFoundError: No module named '...') than test/fixture Exceptions - I have had to explicitly stop/cancel in those cases. Could that be related?

Originally posted by @tboddyspargo in #24594

[eleanorjboyd]

Hello! This should be fixed in 2024.22.1 - it should no longer cause VS Code to stall. But as a result of the workaround for now the issue seen here #24656 will then appear in 2024.22.1. If you have >2 workspaces and >30 tests you should downgrade to 2024.20.*

[tboddyspargo]

Thank you for confirming, @eleanorjboyd - indeed, the "stall" that I'm experiencing sounds very much like #24656. I just didn't know that the reproduction was dependent on the number of tests exceeding ~30! Our workspace has thousands across dozens of folders and the Test Explorer area doesn't seem to go further than the smallest few folders, which presumably complete the fastest and have a total number of tests of ~30 between them, so that checks out!