Discord report (fresh.dumbledore [VRN]): slskd sometimes ships broken files
(truncated transfers, corrupt FLAC, wrong file substituted on filename match).
They flowed through post-processing and only surfaced later — Plex/Jellyfin
scan failures, dead-air playback, duplicate detector tripping over the wrong
length. By that point the file was already tagged, copied, mirrored to the
media server, and recorded in provenance.
New module `core/imports/file_integrity.py`:
- `check_audio_integrity(path, expected_duration_ms=None) -> IntegrityResult`
- Three tiered checks, cheapest to most expensive:
1. File size sanity (catches 0-byte stubs and stub transfers)
2. Mutagen parse (catches header damage, wrong-format-with-right-extension)
3. Duration agreement vs. metadata source's expected length, ±3s tolerance
(5s for tracks over 10 minutes — long tracks naturally drift more)
- Returns IntegrityResult with `ok`, human-readable `reason`, and per-check
`checks` dict for debugging
- Never raises; pathological inputs return ok=False with explanation
Pipeline integration in `core/imports/pipeline.py:post_process_matched_download`:
- Hooks between the existing file-stability wait and AcoustID verification
- On failure: quarantine via existing `move_to_quarantine` helper, mark task
failed with descriptive error, clear matched-context, fire
`on_download_completed(success=False)` so the slot is released for retry
- Mirrors the existing AcoustID-failure path so retry behavior stays consistent
- Wrapped in try/except so an unexpected failure inside the check itself
cannot block downloads — logs and continues
This is intentionally tier 1: universal across formats, no external deps.
A future tier could verify FLAC STREAMINFO MD5 by decoding audio (needs
flac binary or libflac wrapper) — skipped for now since tier 1 catches the
dominant Discord-reported cases (truncated, 0-byte, wrong file).
Tests:
- `tests/imports/test_file_integrity.py` — 14 cases covering all three check
tiers, edge cases (zero/negative expected duration, long-track wider
tolerance, caller tolerance override), and the mutagen-unavailable
degradation path
- `tests/imports/test_import_pipeline.py` — two existing tests use 5-byte
fixture files that the new check would reject; they monkeypatch the
integrity check since they're testing plumbing (notification +
metadata_runtime forwarding), not integrity behavior
WHATS_NEW entry under '2.4.2' dev cycle.
42f3026eef