GetOrAddFolder read libraryPath.LibraryFolders, a navigation collection only
eager-loaded on the local scan path (via GetLibrary). The Jellyfin remote sync
path takes its LibraryPath off the JellyfinLibrary entity, where LibraryFolders
is null, so .Filter(null) threw ArgumentNullException('source') on the first
item of every Jellyfin music-video scan — a feature that had therefore never
run in prod, CI, or locally.
Look the folder up from the DB by (LibraryPathId, Path) instead, removing the
implicit eager-load contract entirely (correct for all nine callers) and
documenting it on ILibraryRepository. null != empty is preserved so a re-scan
does not insert duplicate LibraryFolder rows. No new hot-path cost: local
scanners already query GetParentFolderId per folder just before this call.
Tests:
- LibraryRepositoryTests: GetOrAddFolder with a null LibraryFolders (the exact
remote-path shape) creates the folder, is idempotent on re-scan, and persists
a supplied ParentId.
- JellyfinMusicVideoLibraryScannerTests: an end-to-end scan of one synthetic
music video, wiring the REAL LibraryRepository/ArtistRepository/
MusicVideoRepository against in-memory SQLite (the existing MediaServer*
scanner tests mock every repo, which is why the bug escaped), asserts the scan
completes and creates Artist + MusicVideo rows with a real LibraryFolder.
Both proven non-vacuous against the reverted fix (each reproduces the issue's
ArgumentNullException). decisions.md entry added.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
