fix: FLAC, Ogg and Opus tracks carry their MusicBrainz recording id from the tag: one reader in library gives the scanner, the backfills and the importer the same ids, and the next scan re-reads the library (#5637)

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

internal/library/mbids_test.go

@@ -40,7 +40,8 @@ func TestExtractMBIDs_Vorbis(t *testing.T) {
 			"musicbrainz_artistid": "def",
 		},
 	}
-	a, ar := extractMBIDs(m)
+	ids := ReadTagMBIDs(m)
+	a, ar := ids.Release, ids.Artist
 	if a != "abc" || ar != "def" {
 		t.Errorf("got (%q, %q), want (\"abc\", \"def\")", a, ar)
 	}
@@ -62,7 +63,8 @@ func TestExtractMBIDs_ID3v2(t *testing.T) {
 			},
 		},
 	}
-	a, ar := extractMBIDs(m)
+	ids := ReadTagMBIDs(m)
+	a, ar := ids.Release, ids.Artist
 	if a != "abc-123" || ar != "def-456" {
 		t.Errorf("got (%q, %q), want (\"abc-123\", \"def-456\")", a, ar)
 	}
@@ -78,7 +80,8 @@ func TestExtractMBIDs_MP4(t *testing.T) {
 			"MusicBrainz Artist Id": "def",
 		},
 	}
-	a, ar := extractMBIDs(m)
+	ids := ReadTagMBIDs(m)
+	a, ar := ids.Release, ids.Artist
 	if a != "abc" || ar != "def" {
 		t.Errorf("got (%q, %q), want (\"abc\", \"def\")", a, ar)
 	}
@@ -86,7 +89,8 @@ func TestExtractMBIDs_MP4(t *testing.T) {
 
 func TestExtractMBIDs_MissingTagsReturnEmpty(t *testing.T) {
 	m := stubMeta{format: tag.VORBIS, raw: map[string]interface{}{}}
-	a, ar := extractMBIDs(m)
+	ids := ReadTagMBIDs(m)
+	a, ar := ids.Release, ids.Artist
 	if a != "" || ar != "" {
 		t.Errorf("got (%q, %q), want empty", a, ar)
 	}
@@ -104,7 +108,8 @@ func TestExtractMBIDs_VorbisUppercaseKeysMiss(t *testing.T) {
 			"MUSICBRAINZ_ARTISTID": "wrong-case",
 		},
 	}
-	a, ar := extractMBIDs(m)
+	ids := ReadTagMBIDs(m)
+	a, ar := ids.Release, ids.Artist
 	if a != "" || ar != "" {
 		t.Errorf("uppercase Vorbis keys must not match dhowden output; got (%q, %q)", a, ar)
 	}
@@ -127,7 +132,8 @@ func TestExtractMBIDs_ID3v2StripsTrailingNUL(t *testing.T) {
 			},
 		},
 	}
-	a, ar := extractMBIDs(m)
+	ids := ReadTagMBIDs(m)
+	a, ar := ids.Release, ids.Artist
 	if a != "abc-123" || ar != "def-456" {
 		t.Errorf("got (%q, %q), want trailing NUL stripped", a, ar)
 	}
@@ -146,7 +152,7 @@ func TestExtractMBIDs_ID3v2MultiValueTakesFirst(t *testing.T) {
 			},
 		},
 	}
-	_, ar := extractMBIDs(m)
+	ar := ReadTagMBIDs(m).Artist
 	if ar != "primary-mbid" {
 		t.Errorf("got %q, want %q", ar, "primary-mbid")
 	}
@@ -186,17 +192,53 @@ func TestExtractReleaseGroupMBID(t *testing.T) {
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
-			if got := extractReleaseGroupMBID(c.meta); got != "group-1" {
+			if got := ReadTagMBIDs(c.meta).ReleaseGroup; got != "group-1" {
 				t.Errorf("release group = %q, want group-1", got)
 			}
-			if album, _ := extractMBIDs(c.meta); album != "release-1" {
+			if album := ReadTagMBIDs(c.meta).Release; album != "release-1" {
 				t.Errorf("album (release) = %q, want release-1", album)
 			}
 		})
 	}
 
 	none := stubMeta{format: tag.VORBIS, raw: map[string]interface{}{"musicbrainz_albumid": "release-1"}}
-	if got := extractReleaseGroupMBID(none); got != "" {
+	if got := ReadTagMBIDs(none).ReleaseGroup; got != "" {
 		t.Errorf("untagged release group = %q, want empty", got)
 	}
 }
+
+// #5637: each format's recording id lands in Recording, and the release-track
+// id never does. Picard calls the recording MUSICBRAINZ_TRACKID in Vorbis
+// comments, the name mbz gives the release track.
+func TestReadTagMBIDs_Recording(t *testing.T) {
+	cases := []struct {
+		name string
+		meta stubMeta
+	}{
+		{"vorbis", stubMeta{format: tag.VORBIS, raw: map[string]interface{}{
+			"musicbrainz_trackid":        "rec-1",
+			"musicbrainz_releasetrackid": "reltrack-1",
+		}}},
+		{"id3v2 ufid", stubMeta{format: tag.ID3v2_4, raw: map[string]interface{}{
+			"UFID":   &tag.UFID{Provider: "http://musicbrainz.org", Identifier: []byte("rec-1")},
+			"TXXX_0": &tag.Comm{Description: "MusicBrainz Release Track Id", Text: "reltrack-1\x00"},
+		}}},
+		{"mp4", stubMeta{format: tag.MP4, raw: map[string]interface{}{
+			"MusicBrainz Track Id":         "rec-1",
+			"MusicBrainz Release Track Id": "reltrack-1",
+		}}},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if got := ReadTagMBIDs(c.meta).Recording; got != "rec-1" {
+				t.Errorf("recording = %q, want rec-1", got)
+			}
+		})
+	}
+
+	// A Vorbis file carrying only the release-track id has no recording id.
+	only := stubMeta{format: tag.VORBIS, raw: map[string]interface{}{"musicbrainz_releasetrackid": "reltrack-1"}}
+	if got := ReadTagMBIDs(only).Recording; got != "" {
+		t.Errorf("release track only: recording = %q, want empty", got)
+	}
+}