Follow-up to the salvaged #81201 commits:
- Short-circuit _uses_hermes_python_environment when the child IS the
running interpreter (path or realpath match). The default strict-mode
path no longer spawns a probe subprocess at all, and a flaky probe of
sys.executable can never drop the hermes root from PYTHONPATH
(protects the test_repo_root_modules_are_importable invariant). The
realpath leg also covers uv-style venvs whose bin/python resolves to
the same binary.
- Stop caching failed probes: _python_environment_prefix now uses a
success-only dict cache instead of lru_cache, so one transient
timeout under load no longer sticks for the process lifetime.
- Deduplicate the subprocess probe scaffolding shared with
_is_usable_python into _probe_python().
- Log once when the hermes root is omitted so import-behavior changes
are diagnosable from user reports.
- Tests: fail the composition tests loudly if execute_code never
reaches Popen (was vacuously passing on exceptions); assert the
staging dir is literally first in PYTHONPATH (was truthiness only);
add guards for probe-failure retry and the no-probe short-circuit.
kshitij
89556c63ac