Reported case (CAL): a track already on disk got re-downloaded by the
watchlist scanner on every scan. Library DB had stale album metadata
for the file (track tagged on album "Left Alone") while the metadata
source reported it on a different album ("NPC" single). The
title+artist+album fuzzy block correctly said the album names didn't
match and declared the track missing — but the file's stable external
IDs (Spotify ID, ISRC, etc.) unambiguously identified it as the same
recording.
The earlier compilation-album fix (PR #461) handled qualifier drift
("OST" vs "Music From The Motion Picture"). This case is two
genuinely different album names referring to the same song.
Fix: provider-neutral external-ID short-circuit before the fuzzy
block in `is_track_missing_from_library`. Pulls every recognized ID
off the source track (Spotify / iTunes / Deezer / Tidal / Qobuz /
MusicBrainz / AudioDB / Hydrabase / ISRC), runs a single SELECT
against the indexed external-ID columns on the `tracks` table, and
treats any hit as "track exists in library — don't re-download".
If no IDs are available (older imports without enrichment, library
scans that didn't populate external IDs), falls through to the
existing fuzzy logic so the safety net stays intact.
New `core/library/track_identity.py` module with two helpers:
- `extract_external_ids(track)`: handles dict and object-style track
shapes, direct-field aliases (spotify_id / spotify_track_id /
SPOTIFY_TRACK_ID), and provider-disambiguated native `id` fields
(when track has `provider='deezer'` and `id='X'`, treats X as a
Deezer ID).
- `find_library_track_by_external_id(db, external_ids,
server_source)`: builds an OR of indexed column matches with
IS NOT NULL guards, optional server_source filter that also
passes legacy NULL rows, single-row LIMIT.
ISRC bridges across providers — a library track imported via Deezer
can be matched against a Spotify scan when both sides carry the
same ISRC.
43 regression tests in `tests/test_library_track_identity.py`:
- 9 ID-extraction tests for direct fields (Spotify / iTunes / Deezer /
ISRC / MBID / AudioDB / Hydrabase)
- 8 ID-extraction tests via the provider field (8 providers + source
alias + missing-provider-ignored)
- 7 mixed/defensive tests (multiple IDs, object-style, empty strings,
None track, numeric coercion)
- 8 lookup tests (per-provider + ISRC cross-bridge)
- 3 OR-semantics tests
- 4 server_source filter tests
- 2 ID-column-map sanity tests
Full pytest 1606 passed; ruff clean.
Body byte-identical to the original. Spotify proxy via registry,
iTunes/Deezer client shims wrap registry helpers,
_resolve_library_file_path, _attempt_download_with_candidates, and
missing_download_executor are injected via init() right after
_init_wishlist_failed where all three deps are already defined.
web_server.py: 35239 → 35063 (-176 lines).
Body byte-identical to the original. The shared state dict, lock,
docker_resolve_path helper, and automation engine are injected via
init() at the lift point, where all four originals are already defined.
web_server.py: 37015 → 36833 (-182 lines).
Lifts _search_service and its _detect_provider helper. Both bodies are
byte-identical to the originals. The nine enrichment worker handles
(spotify/itunes/mb/lastfm/genius/tidal/qobuz/discogs/audiodb) are
injected via init() right after qobuz is constructed, which is the
last worker to come up — and well before Flask starts accepting
requests, so the route handlers never see unbound workers.
web_server.py: 37245 → 37015 (-230 lines).
Pulls the 258-line retag worker out of `web_server.py` into a new
`core/library/` package. Pure 1:1 lift — wrapper keeps the original
entry-point name so the retag-trigger endpoint continues to work
without changes.
What `execute_retag` does:
1. Fetch album + track metadata for the new `album_id` (Spotify or
iTunes — the Spotify client transparently falls back).
2. Load existing files in the retag group from the DB.
3. Match each existing track to a new Spotify track:
- Priority 1: same disc + track number.
- Priority 2: title similarity >= 0.6 (SequenceMatcher).
4. For each matched pair:
- Re-write metadata tags via `_enhance_file_metadata`.
- Compute the new path via `_build_final_path_for_track` and move
the audio file (plus .lrc / .txt sidecars) if the path changes.
- Drop an orphaned cover.jpg if it's left in an empty directory.
- Clean up empty parent directories left behind.
- Download the new cover art into the new album dir.
5. Update the retag group record with new artist / album / image /
total_tracks / release_date and the appropriate Spotify-or-iTunes
album ID (numeric → iTunes, alphanumeric → Spotify).
6. Mark the retag state 'finished' (or 'error' on exception).
Strict 1:1 byte parity:
The original mutated `retag_state` as a module global (the function
declared `global retag_state` even though it only mutates in place).
Here `retag_state` is exposed through the `RetagDeps` proxy as a Python
property so the lifted body keeps `name[key] = value` /
`name.update(...)` syntax. The property setter rebinds the
web_server.py reference if the function ever reassigns it (currently
it doesn't, but the setter is wired for parity with the watchlist lift).
Diff vs original after `deps.X` → global X normalization is **zero
differences** apart from the dropped `global retag_state` decl and the
inline `from database.music_database import get_database` (replaced by
deps.get_database()). 258 lines orig = 258 lines lifted, byte-identical
body otherwise.
Dependencies injected via `RetagDeps` (13 fields) — config_manager,
retag_lock, spotify_client, plus 8 callable helpers
(get_audio_quality_string, enhance_file_metadata,
build_final_path_for_track, safe_move_file, cleanup_empty_directories,
download_cover_art, docker_resolve_path, get_database) and 2 property
delegates (_get_retag_state / _set_retag_state).
Tests: 11 new under tests/library/test_retag.py covering setup error
paths (no album data, no album tracks, no existing tracks),
track-number priority match, title-similarity fallback, no-match skip,
missing file skip, file move when path changes, group record update
(spotify vs iTunes ID branching by alphanumeric vs numeric album_id),
multi-disc total_discs computation.
Full suite: 1330 passing (was 1319). Ruff clean.
