fix(ytmusic): reject stale cookie cache writes

external/ytmusic/cookie_provider.go

@@ -36,6 +36,7 @@ type cookieBase struct {
 	mu          sync.Mutex
 	playlists   []playlist.PlaylistInfo
 	trackCache  map[string][]playlist.Track
+	generation  uint64
 	nextLoad    uint64
 	loadCancels map[uint64]context.CancelFunc
 }
@@ -61,6 +62,7 @@ func (b *cookieBase) fetchPlaylists() ([]playlist.PlaylistInfo, error) {
 		b.mu.Unlock()
 		return res, nil
 	}
+	generation := b.generation
 
 	b.mu.Unlock()
 
@@ -77,7 +79,9 @@ func (b *cookieBase) fetchPlaylists() ([]playlist.PlaylistInfo, error) {
 	}
 
 	b.mu.Lock()
+	if b.generation == generation {
 		b.playlists = pls
+	}
 	b.mu.Unlock()
 	return pls, nil
 }
@@ -88,6 +92,7 @@ func (b *cookieBase) fetchTracks(target string) ([]playlist.Track, error) {
 		b.mu.Unlock()
 		return cached, nil
 	}
+	generation := b.generation
 
 	ctx, cancel := context.WithTimeout(context.Background(), cookiePlaylistLoadTimeout)
 	b.nextLoad++
@@ -122,13 +127,16 @@ func (b *cookieBase) fetchTracks(target string) ([]playlist.Track, error) {
 	}
 
 	b.mu.Lock()
+	if b.generation == generation {
 		b.trackCache[target] = tracks
+	}
 	b.mu.Unlock()
 	return tracks, nil
 }
 
 func (b *cookieBase) refresh() {
 	b.mu.Lock()
+	b.generation++
 	for _, cancel := range b.loadCancels {
 		cancel()
 	}
@@ -140,6 +148,7 @@ func (b *cookieBase) refresh() {
 
 func (b *cookieBase) close() {
 	b.mu.Lock()
+	b.generation++
 	for _, cancel := range b.loadCancels {
 		cancel()
 	}

external/ytmusic/cookie_provider_test.go

@@ -335,6 +335,60 @@ func TestCookieProviderStopsTrackLoad(t *testing.T) {
 	}
 }
 
+func TestCookieProviderRefreshRejectsStaleResults(t *testing.T) {
+	t.Run("playlists", func(t *testing.T) {
+		base := newCookieBase("firefox")
+		started := make(chan struct{})
+		release := make(chan struct{})
+		base.fetchFn = func(string) ([]playlist.PlaylistInfo, error) {
+			close(started)
+			<-release
+			return []playlist.PlaylistInfo{{ID: "private"}}, nil
+		}
+		done := make(chan struct{})
+		go func() {
+			_, _ = base.fetchPlaylists()
+			close(done)
+		}()
+
+		<-started
+		base.refresh()
+		close(release)
+		<-done
+		base.mu.Lock()
+		defer base.mu.Unlock()
+		if base.playlists != nil {
+			t.Fatalf("stale playlists cached after refresh: %v", base.playlists)
+		}
+	})
+
+	t.Run("tracks", func(t *testing.T) {
+		base := newCookieBase("firefox")
+		started := make(chan struct{})
+		release := make(chan struct{})
+		base.resolveFn = func(context.Context, string, int, int, ...string) ([]playlist.Track, int, error) {
+			close(started)
+			<-release
+			return []playlist.Track{{Title: "Private"}}, 1, nil
+		}
+		done := make(chan struct{})
+		go func() {
+			_, _ = base.fetchTracks("private")
+			close(done)
+		}()
+
+		<-started
+		base.refresh()
+		close(release)
+		<-done
+		base.mu.Lock()
+		defer base.mu.Unlock()
+		if _, ok := base.trackCache["private"]; ok {
+			t.Fatal("stale tracks cached after refresh")
+		}
+	})
+}
+
 func TestCookieProviderSearchTracksHonorsCancellation(t *testing.T) {
 	if runtime.GOOS == "windows" {
 		t.Skip("skipping Unix shell script test on Windows")