feat: the library's folders are set in Admin › Library, and changing a folder moves its tracks with it, keeping their plays, likes and playlists (#6129)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/minstrel/main.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"slices"
 	"syscall"
 	"time"
 
@@ -135,7 +136,18 @@ func run() error {
 	if fpErr != nil {
 		logger.Warn("fingerprint settings: using defaults", "err", fpErr)
 	}
-	scanner := library.New(pool, logger, cfg.Library.ScanPaths, fpSettings)
+	// The library's folders (#6129): the ones saved in Settings, or
+	// MINSTREL_LIBRARY_SCAN_PATHS until any are. A load failure falls back to
+	// env, which is what the server read before the setting existed.
+	roots, rootsSaved, rootsErr := library.LoadRoots(ctx, pool, cfg.Library.ScanPaths)
+	switch {
+	case rootsErr != nil:
+		logger.Warn("library folders: using MINSTREL_LIBRARY_SCAN_PATHS", "err", rootsErr)
+	case rootsSaved && len(cfg.Library.ScanPaths) > 0 && !slices.Equal(roots, cfg.Library.ScanPaths):
+		logger.Warn("library folders: the ones saved in Settings are used, not MINSTREL_LIBRARY_SCAN_PATHS",
+			"settings", roots, "env", cfg.Library.ScanPaths)
+	}
+	scanner := library.New(pool, logger, roots, fpSettings)
 
 	// Loudness analysis settings (M464 #4995): shared by the loudness backfill
 	// and the admin API, and falls back to the defaults like the above.
@@ -195,7 +207,7 @@ func run() error {
 	// One unified scan chain: library walk → MBID backfill → cover enrich.
 	// Boot-time scan and manual-trigger scans share this path; results land
 	// in scan_runs for the admin overview.
-	if cfg.Library.ScanOnStartup && len(cfg.Library.ScanPaths) > 0 {
+	if cfg.Library.ScanOnStartup && len(roots) > 0 {
 		go func() {
 			if _, err := library.RunScan(ctx, pool, scanner, coverEnricher,
 				logger.With("component", "scan_run"),
@@ -340,7 +352,7 @@ func run() error {
 	if acoustIDSettings != nil {
 		printer = &importer.AcoustIDPrinter{Settings: acoustIDSettings, Client: acoustIDClient}
 	}
-	imp := importer.New(pool, scanner, cat, printer, cfg.Library.ScanPaths, logger.With("component", "import"))
+	imp := importer.New(pool, scanner, cat, printer, scanner.Roots, logger.With("component", "import"))
 	imp.DataDir = cfg.Storage.DataDir
 	go imp.Run(ctx)
 
@@ -431,8 +443,7 @@ func run() error {
 	// Filesystem watcher: near-instant pickup of new/changed files via
 	// fsnotify, scanning just the affected paths + enriching their albums
 	// inline. Replaces the removed configurable scan scheduler.
-	watcher := library.NewWatcher(scanner, coverEnricher,
-		logger.With("component", "watcher"), cfg.Library.ScanPaths)
+	watcher := library.NewWatcher(scanner, coverEnricher, logger.With("component", "watcher"))
 	go func() {
 		if werr := watcher.Run(ctx); werr != nil {
 			logger.Warn("library watcher exited", "err", werr)