A Find & Add on a file-import (CSV/M3U/TXT) playlist track was silently dropped and
the track re-appeared as 'extra' (radoslav-orlov). Root cause: unlike Spotify/YouTube
(native ids), file-import + iTunes-only tracks arrive with an EMPTY source_track_id —
and the whole manual-match system keys on it. _persist_find_and_add_match is a no-op
on an empty id, and find_manual_library_match_by_source_track_id returns None for one,
so the match can be neither recorded nor looked up. That's the youtube-vs-file
difference the reporter noticed.
Fix: stable_source_track_id() derives a DETERMINISTIC 'file:<hash>' id from the track
identity (artist|title|album, normalized) when there's no native id; mirror_playlist
assigns it so the SAME song gets the SAME id across re-imports/discovery — exactly
what the match lookup needs. Native ids are used verbatim; bonus: discovery extra_data
now survives a re-import for these tracks too.
Tests: helper (native passthrough, deterministic + case/field-insensitive, distinct
per song, empty-on-no-title, file: prefix); mirror_playlist integration (file tracks
get stable distinct ids, stable across re-import, native ids untouched). 319 playlist/
sync/discovery/mirrored tests green.
6e622d30f1