Fix path-only Python project manager defaults

[Atomie CHEN (atomiechen)]

Summary

Fixes #1666.

Path-only entries are valid according to the python-envs.pythonProjects setting schema:

{
    "python-envs.pythonProjects": [
        {
            "path": "backend"
        }
    ]
}

However, the manager-setting helpers called .length on the omitted envManager and packageManager properties. This caused repeated TypeError failures during post-initialization telemetry and environment lookup.

Fix

• Treat omitted or empty project-level manager values as requests to use the corresponding default setting.
• Mark PythonProjectSettings.envManager and .packageManager optional so the internal type matches the contributed JSON schema.
• Add a unit test covering a path-only nested project entry and both default-manager fallbacks.

Validation

• Reproduced with VS Code 1.130.0 and the latest stable extensions in an empty --user-data-dir / --extensions-dir profile.
• Installed the patched 1.37.0 VSIX in a second empty profile and verified that the same workspace starts without TypeError or post-initialization failure.
• npm run compile-tests
• npm run lint
• npm run unittest — 1,429 passing, 6 pending

AI disclosure: Prepared with assistance from OpenAI Codex.

[Atomie CHEN (atomiechen)]

@microsoft-github-policy-service agree

[Heejae Chang (heejaechang)]

🔒 Automated review in progress — Heejae Chang (@heejaechang) is auto-reviewing this PR.

[Heejae Chang (heejaechang)]

Info · Optional note

The fallback test covers omitted manager values but not explicitly empty strings, despite the PR claiming both cases. Consider adding empty-string assertions to preserve that behavior explicitly.

[verified]

[Heejae Chang (heejaechang)]

Approved via Review Center.

[Heejae Chang (heejaechang)]

Verification: The relevant tests could not be fully run in the isolated environment; this review is not fully verified.

[Eleanor Boyd (eleanorjboyd)]

Thanks Atomie CHEN (@atomiechen) ! Sorry this has become stale, if you update it for the merge conflict I can approve and we can get this merged!

[Atomie CHEN (atomiechen)]

Eleanor Boyd (@eleanorjboyd) The merge conflict is resolved and the PR is ready for another look when you have time. Thanks for offering to review it.

Updated this PR with the latest upstream main and resolved the conflict caused by the project settings type move. The fix now marks the manager fields optional in src/features/projectManager.ts. I also added coverage for explicitly empty manager values, as suggested in review.

Local validation: npm run compile-tests, npm run lint, npm run compile, and npm run unittest (2,413 passing, 11 pending). GitHub now reports the PR as mergeable. The new CI workflows are awaiting maintainer approval before they can run.

AI disclosure: OpenAI Codex assisted with the conflict resolution and the additional regression test. The merge commit records this with an AI-Assisted-By trailer.

[Eleanor Boyd (eleanorjboyd)]

🤖 Re-reviewed the updated PR. The manager fields are now optional in the project settings type, both lookup helpers fall back correctly for omitted or empty values, and the added unit tests cover both cases. I found no blocking issue in the changes. CI is still pending; this approval does not replace a green run.