Previous commit only populated `artists.aliases` for artists the MB
worker had enriched. But the AcoustID verifier (next commit) needs
aliases for ANY expected artist — including:
- Artists not yet in the user's library (first download)
- Artists in the library where MB enrichment hasn't run yet
- Artists where MB enrichment ran but found no MBID (NULL aliases)
This commit adds a multi-tier resolution helper that fills those
gaps without thrashing the MB API.
# Multi-tier resolution
`lookup_artist_aliases(artist_name) -> list[str]`:
1. **Library DB** (fast path): existing `get_artist_aliases` lookup
by name. No network. Most common path once the worker has
enriched everything.
2. **Cache** (existing `musicbrainz_cache` table, entity_type=
`artist_aliases`): a prior live lookup for this name. Empty
cache hit is respected (don't re-query when MB previously had
nothing).
3. **Live MB**: search artist by name → pick highest-confidence
match (combined name-similarity + MB relevance) → fetch aliases
for that MBID → cache the result.
Always returns a list (possibly empty), never raises. Empty result
on any tier means "no alternate spellings found, fall back to
direct match" — identical to the pre-fix behaviour.
# Threshold gate
Live lookup only trusts the MB search result when combined
similarity score >= 0.6. Below that, we'd be guessing at the wrong
artist — searching `John Smith` returns multiple John Smiths and
pulling aliases for one of them could mismatch. Cache the empty
result so we don't keep re-searching the same low-confidence name.
# Performance contract
Critical for the verifier path: 100 quarantine candidates with the
same expected artist must NOT trigger 100 MB API calls. Cache hit
on second + subsequent calls per unique artist name. Verified by
test pinning the call counts.
# Tests added (8)
- Tier 1 library DB hit — no MB API call fired
- Tier 3 live MB lookup → search → fetch → returns aliases
- Tier 2 cache hit on second call — no re-query
- Empty input → empty return + no API call
- Network failure on search → empty + cached so we don't retry
- No search results → empty + cached
- Low-confidence match (sim < 0.6) skipped — defends against
picking the wrong artist
- Library row exists but aliases NULL → falls through to live
lookup (defends against the half-enriched state)
# Verification
- 31/31 service tests pass (8 new + 23 prior)
- Ruff clean
Issue #442 — MusicBrainz exposes alternate-spelling aliases (Japanese
kanji `澤野弘之` for `Hiroyuki Sawano`, Cyrillic `Сергей Лазарев` for
`Sergey Lazarev`, etc.) on every artist record. SoulSync's MB
enrichment worker had access to this data via `get_artist(mbid,
includes=['aliases'])` but wasn't reading or persisting it.
This commit wires the alias fetch into the worker's existing
artist-match path, persists to the new `artists.aliases` column
added in the prior commit, and adds a verifier-friendly read-by-
name lookup so the AcoustID verifier (next commit) can resolve
aliases without an MB round-trip when the artist is in the library.
# New service methods
- `fetch_artist_aliases(mbid) -> list[str]` — calls
`mb_client.get_artist(mbid, includes=['aliases'])`, parses the
alias array, dedupes case-insensitively. Returns empty list on
any failure (missing key, network error, malformed response) so
transient MB outages never trigger stricter quarantine decisions
than the pre-fix behaviour. Empty mbid → no API call.
- `update_artist_aliases(artist_id, aliases)` — persists as JSON
array to `artists.aliases`. Idempotent — overwrites prior value.
Empty list clears the column. None artist_id is a no-op.
- `get_artist_aliases(artist_name) -> list[str]` — reads back by
artist NAME (not id), case-insensitive. Used by the verifier
where the expected artist comes from track metadata — there's no
library row id at quarantine time. Returns empty list for unknown
artists, missing data, or corrupt JSON (defensive against legacy
rows).
# Worker integration
`MusicBrainzWorker._process_item` artist branch:
- After `update_artist_mbid` succeeds, fetch aliases for the matched
MBID and persist via `update_artist_aliases`.
- Best-effort: alias fetch wrapped in try/except, failure logs at
debug level, doesn't regress the match outcome.
- No alias call when the artist didn't match an MBID (nothing to
enrich).
# Tests (23)
- `fetch_artist_aliases`: extracts names from MB response,
case-insensitive dedup, skips empty/null entries, missing-key
fallback, network failure → empty, empty mbid no API call,
verifies `inc=aliases` request param.
- `update_artist_aliases`: persists as JSON, idempotent overwrite,
empty list clears column, None id is no-op.
- `get_artist_aliases`: returns aliases for known artist,
case-insensitive lookup, empty for unknown artist / no-aliases
row, handles corrupt JSON + non-list shape gracefully.
- Worker integration: matched artist triggers fetch + persist,
no alias call when not matched, alias-fetch failure doesn't
break the match outcome.
# Verification
- 23/23 new tests pass
- Ruff clean
Issue #442 — files tagged with one spelling of an artist's name
(Japanese kanji `澤野弘之`) get quarantined when SoulSync expects the
romanized spelling (`Hiroyuki Sawano`). Raw similarity comparison
scored 0% across scripts. MusicBrainz exposes alternate-spelling
aliases on every artist record but the verifier never consulted
them.
This commit adds the pure helper that does the alias-aware
comparison. No I/O, no DB access, no network. Caller supplies the
aliases (looked up from library DB or live MB by later commits in
this PR). Default threshold matches the verifier's existing
`ARTIST_MATCH_THRESHOLD` (0.6) so wiring this in preserves current
pass/fail semantics on the no-alias path.
# API
```
artist_names_match(expected, actual, *, aliases=None,
threshold=0.6, similarity=None)
-> (matched: bool, best_score: float)
```
- Direct compare first (fast path + baseline score)
- If below threshold, score each alias against `actual`
- First alias to clear threshold → match
- Returns the best score across all candidates so callers can log
the score they made the decision on
```
best_alias_match(expected, actual, aliases=None, *, similarity=None)
-> (winner: Optional[str], best_score: float)
```
Companion helper for callers that want to surface WHICH alias
triggered the match (debug logs, UI explanations). No threshold —
purely informative.
# Architectural choices
- **Pure function**: no I/O. Caller (verifier, future matching-engine
consumers) owns alias lookup strategy + threshold tuning.
- **Custom similarity callable**: lets the verifier pass its
parenthetical-stripping normaliser without this module having to
know about it. Defaults to lowercase + SequenceMatcher (matches
the verifier's existing behaviour).
- **Defensive coercion**: aliases input handles None entries, empty
strings, non-string types, sets, tuples, lists — caller may feed
raw MB response data without cleaning first.
- **Backward compat**: `aliases=None` or empty → behaves identically
to a plain similarity check. Paths not yet wired up to alias lookup
see no behaviour change.
# Tests (28)
- Direct compare (no aliases): exact / case / whitespace / fuzzy /
different
- Cross-script with aliases: Japanese ↔ romanized (reporter's case 1),
Cyrillic ↔ Latin (reporter's case 2), symmetric direction, no-match
fallthrough so aliases don't mask genuine mismatches
- Aliases input handling: None, empty, set, tuple, None-entries,
non-string entries
- Threshold: default matches verifier's 0.6, custom stricter, custom
looser
- Custom similarity: applies to both direct + alias compare
- Best-alias-match introspection
- Backward compat parametrised across 5 cases
# What this commit does NOT do
This is the helper module + tests only. Subsequent commits in this
PR populate aliases (MB worker), provide live MB lookup with cache
for un-enriched artists, and wire the helper into the AcoustID
verifier where the quarantine decision actually fires.
Broque Thomas