Pipeline-driven Auto-Sync runs against any ListenBrainz playlist
(Weekly Jams, Weekly Exploration, Top Discoveries, etc.) would sit
on ``Refreshing: "<name>"`` with no UI updates for 5-7 minutes
before the pipeline progressed. Two real bugs stacked:
1. **Double discovery.** The refresh handler called
``_maybe_discover`` (matching engine, per-track Spotify/iTunes/
Deezer matches) inline for any source returning
``needs_discovery=True`` tracks. Phase 2 of the pipeline then
ran the SAME matching engine via ``run_playlist_discovery_worker``
on the same tracks. The refresh-side run blocked the loop with
zero progress emission; Phase 2's already has the timed
progress-poll pattern. So LB tracks discovered twice, the first
time silently.
Pipeline now sets ``skip_discovery=True`` on its refresh config.
The handler honors the flag and lets Phase 2 handle discovery
end-to-end. Standalone callers (Sync-page tab, registration
action) leave the flag unset so they still get matched_data
on refresh.
2. **No targeted LB refresh.** The LB adapter's ``refresh_playlist``
called ``manager.update_all_playlists()`` — the only refresh
entry-point the manager exposed — which re-pulls every cached
LB playlist's details from the API (~12+ round-trips) even
when only one playlist needed refreshing. Wasteful;
tax-on-everyone for one-playlist work.
Added ``LBManager.refresh_playlist(mbid)`` — reads the cached
playlist_type, fetches just that playlist's details, runs the
normal ``_update_playlist`` upsert path. Defaults type to
``user`` for un-cached mbids so new-playlist discovery still
works. Skips ``_cleanup_old_playlists`` and
``_ensure_rolling_mirrors_from_cache`` (wasted work for a
single-playlist refresh).
Also: killed a silent ``except Exception: pass`` in the LB
adapter's old refresh wrapper that was masking every LB API
failure as a stale-cache hit. Refresh errors now log with full
traceback at warning level and propagate ``None`` so the outer
handler at ``refresh_mirrored.py:104`` counts the error and
surfaces it to the run-history error tally.
Pinned with 12 new unit tests across:
- ``tests/test_listenbrainz_manager.py`` (8): targeted refresh
happy path, unauthenticated guard, empty-mbid guard, upstream
``None`` return, default playlist_type for unknown mbid,
exception propagation, cost guard skipping cleanup, skipped-
when-unchanged signal
- ``tests/test_playlist_sources_adapters.py`` (3): adapter uses
targeted call (not legacy), adapter returns ``None`` on manager
error (not silent swallow), adapter resolves synthetic series
ids before calling the manager
- ``tests/automation/test_handlers_playlist.py`` (1):
skip_discovery flag bypasses ``_maybe_discover`` end-to-end
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