Follow-up to #73907 (probe timeout 15s + env override + timeout-only
retry), widening the same fix to the two sibling sites it missed:
- backendSupportsServe's serve --help probe kept a bare execFileSync
with its own 15s literal: same cold-Windows Python-startup class
(#72632 measured ~10.5s for --version cold), no retry, and a false
negative is cached for the process lifetime - silently routing a
modern runtime through the legacy dashboard form. Route it through
execProbeSync with the shared PROBE_TIMEOUT_MS (honours
HERMES_PROBE_TIMEOUT_MS) and the timeout-only retry.
- resolveHermesBackend step 4 called unwrapWindowsVenvHermesCommand
twice; the second call re-ran the same un-memoized import probe,
costing up to another full probe timeout on a hung interpreter for
an answer the first call already gave. Drop the redundant re-probe.
Part of the #72707 bug class (transient disconnect must not strand a
healthy install).
The old test asserted _warm_gateway_module was fire-and-forget (startup
completes in << SLOW_SECONDS). PR #73291 intentionally reversed this:
the import now runs synchronously before the lifespan yield because
run_in_executor didn't release the GIL on Windows + Python 3.11.
Updated the test to assert startup blocks for >= SLOW_SECONDS.
Treat HERMES_DESKTOP_HERMES as an authoritative deployment override.
This keeps the Nix desktop package on its matching immutable Hermes CLI
instead of falling through to install.sh when a best-effort version probe
fails or times out.
kshitijk4poor