enhance_file_metadata rebuilds tags from scratch: for FLAC it calls
clear_pictures(), for MP3/MP4 it clears the whole tag block — and it does
this UP FRONT, then saves the file, long before it tries to fetch and embed
the replacement art. So every way the re-embed could come up empty left the
file saved with the original art destroyed and nothing put back:
- extract_source_metadata returns nothing -> early save, no embed
- no album-art URL / art download fails / rejected by the min-size guard
-> embed_album_art_metadata returns early without adding a picture
- art embedding disabled in config -> embed skipped entirely
- embed raises mid-enrichment -> file left cleared on disk
This is the "cover art gets corrupted/destroyed during import" half of #764
(continuation of #755); distinct from #750's truncated-cache DISPLAY bug.
Fix: new core/metadata/art_preservation.py snapshots the existing art
(the live Picture / APIC / MP4Cover objects, so they re-apply verbatim)
BEFORE the clear, and restores it before each save IFF the file currently
has none. Wired into all three exit paths in enhance_file_metadata
(no-metadata early return, the final save, and the except handler). The
restore is a strict no-op when art is already present, so the happy path —
new art embedded — is byte-for-byte unchanged: it never clobbers or
duplicates a freshly-embedded cover. embed_album_art_metadata now returns a
bool so the intent (embedded / didn't) is explicit.
Tests:
- tests/test_art_preservation.py (5) — snapshot/restore round-trips through
real mutagen FLAC + ID3 objects; restore no-ops when new art is present.
- tests/test_enrichment_art_preservation.py (4) — runs the REAL
enhance_file_metadata over a real FLAC with embedded art and asserts the
art survives on disk for missing-metadata / failed-embed / embed-raises,
and is correctly REPLACED (exactly one picture, new bytes) on success.
1019 tests pass across the metadata/enrichment/imports/acoustid suites.
