fix(lyrics): keep V3 collaborations on the primary side

test/lyrics_parser_test.dart

@@ -50,6 +50,20 @@ ${_tag('translation', 2000, 'Second translation')}
     expect(backing.vocalGroup, lyrics.lines.first.vocalGroup);
   });
 
+  test('V3 is a collaboration even without TTML group metadata', () {
+    for (final source in [
+      '[00:01.00]V1:Lead\n[00:02.00]V3:Together\n[00:03.00]V2:Guest',
+      '<tt xmlns:m="http://www.w3.org/ns/ttml#metadata"><body>'
+          '<p begin="1s" m:agent="v1">Lead</p>'
+          '<p begin="2s" m:agent="v3">Together</p>'
+          '<p begin="3s" m:agent="v2">Guest</p></body></tt>',
+    ]) {
+      final lyrics = LyricsParser.parse(source);
+      expect(lyrics.lines[1].voice?.isGroup, isTrue);
+      expect(lyrics.lines[2].voice?.isGroup, isFalse);
+    }
+  });
+
   test(
     'backing groups survive sorting, offsets and repeated backing parts',
     () {

test/now_playing_lyrics_transition_test.dart

@@ -2707,50 +2707,51 @@ void main() {
   }
 
   for (final mornye in [false, true]) {
-    testWidgets('TTML group vocals keep the primary side ($mornye)', (
-      tester,
-    ) async {
-      metadataOverrides['lyrics'] = '''
+    testWidgets(
+      'TTML V3 without group metadata keeps the primary side ($mornye)',
+      (tester) async {
+        metadataOverrides['lyrics'] = '''
 <tt xmlns="http://www.w3.org/ns/ttml" xmlns:m="http://www.w3.org/ns/ttml#metadata">
-<head><metadata><m:agent xml:id="v1" type="person"/><m:agent xml:id="v2" type="person"/><m:agent xml:id="v3" type="group"/></metadata></head>
+<head><metadata><m:agent xml:id="v1" type="person"/><m:agent xml:id="v3" type="person"/><m:agent xml:id="v2" type="person"/></metadata></head>
 <body><p begin="1s" end="3s" m:agent="v2">Guest</p><p begin="3s" end="6s" m:agent="v3">Together</p><p begin="6s" end="9s" m:agent="v2">Guest returns</p></body></tt>
 ''';
-      final playback = StreamController<PlaybackState>.broadcast();
-      addTearDown(playback.close);
-      await pumpNowPlaying(
-        tester,
-        theme: mornye ? MornyeTheme.build(Brightness.dark) : null,
-        size: const Size(390, 1100),
-        playbackEvents: playback.stream,
-      );
-      mediaItems.add(item('first'));
-      await tester.pumpAndSettle();
-      if (mornye) {
-        await tester.tap(find.byIcon(CupertinoIcons.quote_bubble));
-      } else {
-        await tester.drag(find.byType(PageView), const Offset(-350, 0));
-      }
-      await tester.pumpAndSettle();
-      for (final seconds in [0, 2, 4, 7, 4]) {
-        playback.add(
-          PlaybackState(
-            playing: false,
-            processingState: AudioProcessingState.ready,
-            updatePosition: Duration(seconds: seconds),
-          ),
+        final playback = StreamController<PlaybackState>.broadcast();
+        addTearDown(playback.close);
+        await pumpNowPlaying(
+          tester,
+          theme: mornye ? MornyeTheme.build(Brightness.dark) : null,
+          size: const Size(390, 1100),
+          playbackEvents: playback.stream,
         );
+        mediaItems.add(item('first'));
         await tester.pumpAndSettle();
-        expect(
-          tester.widget<Text>(find.text('Together')).textAlign,
-          TextAlign.left,
-        );
-        expect(
-          tester.widget<Text>(find.text('Guest returns')).textAlign,
-          TextAlign.right,
-        );
-      }
-      expect(tester.takeException(), isNull);
-    });
+        if (mornye) {
+          await tester.tap(find.byIcon(CupertinoIcons.quote_bubble));
+        } else {
+          await tester.drag(find.byType(PageView), const Offset(-350, 0));
+        }
+        await tester.pumpAndSettle();
+        for (final seconds in [0, 2, 4, 7, 4]) {
+          playback.add(
+            PlaybackState(
+              playing: false,
+              processingState: AudioProcessingState.ready,
+              updatePosition: Duration(seconds: seconds),
+            ),
+          );
+          await tester.pumpAndSettle();
+          expect(
+            tester.widget<Text>(find.text('Together')).textAlign,
+            TextAlign.left,
+          );
+          expect(
+            tester.widget<Text>(find.text('Guest returns')).textAlign,
+            TextAlign.right,
+          );
+        }
+        expect(tester.takeException(), isNull);
+      },
+    );
 
     for (final ttml in [false, true]) {
       testWidgets(