Adds an opt-in `rank_candidates_by_quality` profile flag. When on, the
priority-mode download walk orders candidates by the ranked-target quality
(confidence/speed only break ties) instead of confidence-first. Default off
keeps the byte-for-byte old behaviour, so existing installs are unaffected.
Best-quality search mode is always quality-first regardless of the flag; the
toggle only affects priority mode. Search-time source selection is unchanged —
nothing is skipped, so a track can never go missing, only the order in which
copies are tried changes.
The version-mismatch force-import follows automatically: it accepts the
first-tried (= best-ordered) quarantined candidate, which is the highest-quality
one once the walk is quality-first. No change to its selection logic needed.
- core/quality/selection.py: load_rank_candidates_by_quality() (fail-closed).
- core/downloads/task_worker.py: _best_quality_ordering -> _candidate_ordering;
quality-first when best_quality mode OR the toggle is on.
- database/music_database.py: default profile carries the flag (False).
- web_server.py: flag is preserved globally across preset apply/reset, like
search_mode.
- core/imports/version_mismatch_fallback.py: comment clarified (no behaviour
change).
Tests (TDD): load_rank_candidates_by_quality default/enabled/disabled/error;
_candidate_ordering across all mode+toggle combinations + fail-closed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Adds an opt-in search strategy toggle in the Quality Profile:
- priority (default): unchanged — first source in the hybrid chain that
meets a quality target wins.
- best_quality: pool candidates from EVERY source per query and download
them best→worst by actual audio quality; source order only breaks ties.
Implementation reuses existing plumbing so the retry system is untouched:
- engine.search_all_sources pools raw tracks across all configured,
non-exhausted sources (no first-source short-circuit).
- candidates.order_candidates: new quality_first sort path — profile
quality rank dominates, confidence/peer signals break ties. Priority
path is byte-for-byte unchanged (regression-locked by tests).
- task_worker passes quality_first + targets through; skips the redundant
hybrid-fallback block in best-quality mode (pool already covered it).
- Per-source retry budgets unchanged: a source that spends its budget is
added to exhausted_download_sources and thus dropped from the whole
pool. Independent of post_processing.retry_exhaustive.
- Query generator NOT touched.
Also clarifies the "Allow fallback" setting wording: it accepts OFF-LIST
quality as a last resort (not "walk down my list"), and notes that
lossy_copy.downsample_hires also bypasses the quality gate — the cause of
16-bit/MP3 files slipping through a 24-bit-only profile.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
