Follow-up hardening to #789. The selection was keyed purely by folder name,
so renaming a music folder in Navidrome silently reverted the scan to all
libraries. Now persist the folder id (stable across renames) as the primary
key alongside the name (kept for display + back-compat), and restore by id
first with a name fallback. Self-heals on reconnect: pre-id installs and
drifted/renamed names get the id + fresh name written back, so the settings
dropdown keeps highlighting the right folder.
Tests: restore-by-id-after-rename (+ name heal), name-fallback self-heals id,
no-drift writes nothing.
The saved music-folder selection was silently dropped on every reconnect.
_setup_client's restore step called the public get_music_folders(), which
starts with ensure_connection() — but we're already inside ensure_connection()
at that point (_is_connecting=True, _connection_attempted not yet set), so the
re-entrant call bailed and returned []. The restore matched nothing,
music_folder_id stayed None, and the per-call musicFolderId filters all
no-op'd → scans imported every library regardless of the user's choice.
Surfaces after any restart or settings save (reload_config resets the state).
Split get_music_folders() into the public method (does the connection check)
and a non-reentrant _fetch_music_folders() seam; the restore now calls the
seam directly (connection is already established + ping succeeded by then).
Regression + seam tests added.
Expose Navidrome album coverArt as a Subsonic getCoverArt thumbnail so library refreshes keep a real album-art URL. Preserve existing album thumb_url when an incoming server album has no thumbnail, preventing manual or server-corrected covers from being cleared and later replaced by loose missing-cover searches. Add regression tests for Navidrome album thumbnails and DB thumb preservation.
4 tests pin the Navidrome client surface. Auth shape: base_url +
username + password (no token model — salt generated per request).
get_all_album_ids paginates getAlbumList2 and returns a set of
string ids matching cross-server uniform set semantics.
