fix(scanner): Apple Music playlists import for songs with accented characters (#4385)

* fix: resolve playlist import issues with Unicode character paths

Fixes #3332 where songs with accented characters failed to import from Apple Music M3U playlists. The issue occurred because Apple Music exports use NFC Unicode normalization while macOS filesystem stores paths in NFD normalization.

Added normalizePathForComparison() function that normalizes both filesystem and M3U playlist paths to NFC form before comparison. This ensures consistent path matching regardless of the Unicode normalization form used.

Changes include comprehensive test coverage for Unicode normalization scenarios with both NFC and NFD character representations.

* address comments

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(tests): add check for unequal original Unicode paths in playlist normalization tests

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

core/playlists.go

@@ -21,6 +21,7 @@ import (
 	"github.com/navidrome/navidrome/model/criteria"
 	"github.com/navidrome/navidrome/model/request"
 	"github.com/navidrome/navidrome/utils/slice"
+	"golang.org/x/text/unicode/norm"
 )
 
 type Playlists interface {
@@ -203,10 +204,10 @@ func (s *playlists) parseM3U(ctx context.Context, pls *model.Playlist, folder *m
 		}
 		existing := make(map[string]int, len(found))
 		for idx := range found {
-			existing[strings.ToLower(found[idx].Path)] = idx
+			existing[normalizePathForComparison(found[idx].Path)] = idx
 		}
 		for _, path := range paths {
-			idx, ok := existing[strings.ToLower(path)]
+			idx, ok := existing[normalizePathForComparison(path)]
 			if ok {
 				mfs = append(mfs, found[idx])
 			} else {
@@ -223,6 +224,13 @@ func (s *playlists) parseM3U(ctx context.Context, pls *model.Playlist, folder *m
 	return nil
 }
 
+// normalizePathForComparison normalizes a file path to NFC form and converts to lowercase
+// for consistent comparison. This fixes Unicode normalization issues on macOS where
+// Apple Music creates playlists with NFC-encoded paths but the filesystem uses NFD.
+func normalizePathForComparison(path string) string {
+	return strings.ToLower(norm.NFC.String(path))
+}
+
 // TODO This won't work for multiple libraries
 func (s *playlists) normalizePaths(ctx context.Context, pls *model.Playlist, folder *model.Folder, lines []string) ([]string, error) {
 	libRegex, err := s.compileLibraryPaths(ctx)

core/playlists_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/navidrome/navidrome/tests"
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
+	"golang.org/x/text/unicode/norm"
 )
 
 var _ = Describe("Playlists", func() {
@@ -186,6 +187,54 @@ var _ = Describe("Playlists", func() {
 			Expect(pls.Tracks).To(HaveLen(1))
 			Expect(pls.Tracks[0].Path).To(Equal("abc/tEsT1.Mp3"))
 		})
+
+		It("handles Unicode normalization when comparing paths", func() {
+			// Test case for Apple Music playlists that use NFC encoding vs macOS filesystem NFD
+			// The character "è" can be represented as NFC (single codepoint) or NFD (e + combining accent)
+
+			const pathWithAccents = "artist/Michèle Desrosiers/album/Noël.m4a"
+
+			// Simulate a database entry with NFD encoding (as stored by macOS filesystem)
+			nfdPath := norm.NFD.String(pathWithAccents)
+			repo.data = []string{nfdPath}
+
+			// Simulate an Apple Music M3U playlist entry with NFC encoding
+			nfcPath := norm.NFC.String("/music/" + pathWithAccents)
+			m3u := strings.Join([]string{
+				nfcPath,
+			}, "\n")
+			f := strings.NewReader(m3u)
+
+			pls, err := ps.ImportM3U(ctx, f)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(pls.Tracks).To(HaveLen(1), "Should find the track despite Unicode normalization differences")
+			Expect(pls.Tracks[0].Path).To(Equal(nfdPath))
+		})
+	})
+
+	Describe("normalizePathForComparison", func() {
+		It("normalizes Unicode characters to NFC form and converts to lowercase", func() {
+			// Test with NFD (decomposed) input - as would come from macOS filesystem
+			nfdPath := norm.NFD.String("Michèle") // Explicitly convert to NFD form
+			normalized := normalizePathForComparison(nfdPath)
+			Expect(normalized).To(Equal("michèle"))
+
+			// Test with NFC (composed) input - as would come from Apple Music M3U
+			nfcPath := "Michèle" // This might be in NFC form
+			normalizedNfc := normalizePathForComparison(nfcPath)
+
+			// Ensure the two paths are not equal in their original forms
+			Expect(nfdPath).ToNot(Equal(nfcPath))
+
+			// Both should normalize to the same result
+			Expect(normalized).To(Equal(normalizedNfc))
+		})
+
+		It("handles paths with mixed case and Unicode characters", func() {
+			path := "Artist/Noël Coward/Album/Song.mp3"
+			normalized := normalizePathForComparison(path)
+			Expect(normalized).To(Equal("artist/noël coward/album/song.mp3"))
+		})
 	})
 
 	Describe("InPlaylistsPath", func() {