Prevent creation of new sessions if the Timeline is empty.

We currently create sessions based on the placeholder window
index. This shouldn't be needed as we now set a non-empty
timeline as soon as the first MediaItem is added to the playlist.

Once this check is part of the session manager, we can also remove
the equivalent workarounds from the various code integrations.

PiperOrigin-RevId: 369432853

library/core/src/main/java/com/google/android/exoplayer2/analytics/DefaultPlaybackSessionManager.java

@@ -105,6 +105,10 @@ public final class DefaultPlaybackSessionManager implements PlaybackSessionManag
   @Override
   public synchronized void updateSessions(EventTime eventTime) {
     Assertions.checkNotNull(listener);
+    if (eventTime.timeline.isEmpty()) {
+      // Don't try to create new sessions for empty timelines.
+      return;
+    }
     @Nullable SessionDescriptor currentSession = sessions.get(currentSessionId);
     if (eventTime.mediaPeriodId != null && currentSession != null) {
       // If we receive an event associated with a media period, then it needs to be either part of
@@ -234,6 +238,11 @@ public final class DefaultPlaybackSessionManager implements PlaybackSessionManag
 
   @RequiresNonNull("listener")
   private void updateCurrentSession(EventTime eventTime) {
+    if (eventTime.timeline.isEmpty()) {
+      // Clear current session if the Timeline is empty.
+      currentSessionId = null;
+      return;
+    }
     @Nullable SessionDescriptor previousSessionDescriptor = sessions.get(currentSessionId);
     SessionDescriptor currentSessionDescriptor =
         getOrAddSession(eventTime.windowIndex, eventTime.mediaPeriodId);

library/core/src/main/java/com/google/android/exoplayer2/analytics/PlaybackStatsListener.java

@@ -240,7 +240,7 @@ public final class PlaybackStatsListener
     if (events.size() == 0) {
       return;
     }
-    maybeAddSessions(player, events);
+    maybeAddSessions(events);
     for (String session : playbackStatsTrackers.keySet()) {
       Pair<EventTime, Boolean> eventTimeAndBelongsToPlayback = findBestEventTime(events, session);
       PlaybackStatsTracker tracker = playbackStatsTrackers.get(session);
@@ -281,17 +281,15 @@ public final class PlaybackStatsListener
     }
   }
 
-  private void maybeAddSessions(Player player, Events events) {
+  private void maybeAddSessions(Events events) {
-    boolean isCompletelyIdle =
-        player.getCurrentTimeline().isEmpty() && player.getPlaybackState() == Player.STATE_IDLE;
     for (int i = 0; i < events.size(); i++) {
       @EventFlags int event = events.get(i);
       EventTime eventTime = events.getEventTime(event);
       if (event == EVENT_TIMELINE_CHANGED) {
         sessionManager.updateSessionsWithTimelineChange(eventTime);
-      } else if (!isCompletelyIdle && event == EVENT_POSITION_DISCONTINUITY) {
+      } else if (event == EVENT_POSITION_DISCONTINUITY) {
         sessionManager.updateSessionsWithDiscontinuity(eventTime, discontinuityReason);
-      } else if (!isCompletelyIdle) {
+      } else {
         sessionManager.updateSessions(eventTime);
       }
     }

library/core/src/test/java/com/google/android/exoplayer2/analytics/DefaultPlaybackSessionManagerTest.java

@@ -59,6 +59,16 @@ public final class DefaultPlaybackSessionManagerTest {
     sessionManager.setListener(mockListener);
   }
 
+  @Test
+  public void updatesSession_withEmptyTimeline_doesNotCreateNewSession() {
+    EventTime eventTime =
+        createEventTime(Timeline.EMPTY, /* windowIndex= */ 0, /* mediaPeriodId */ null);
+
+    sessionManager.updateSessions(eventTime);
+
+    verifyNoMoreInteractions(mockListener);
+  }
+
   @Test
   public void updateSessions_withoutMediaPeriodId_createsNewSession() {
     Timeline timeline = new FakeTimeline();
@@ -486,8 +496,6 @@ public final class DefaultPlaybackSessionManagerTest {
 
   @Test
   public void belongsToSession_withSameWindowIndex_returnsTrue() {
-    EventTime eventTime =
-        createEventTime(Timeline.EMPTY, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
     Timeline timeline = new FakeTimeline();
     EventTime eventTimeWithTimeline =
         createEventTime(timeline, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
@@ -496,11 +504,10 @@ public final class DefaultPlaybackSessionManagerTest {
             timeline.getUidOfPeriod(/* periodIndex= */ 0), /* windowSequenceNumber= */ 0);
     EventTime eventTimeWithMediaPeriodId =
         createEventTime(timeline, /* windowIndex= */ 0, mediaPeriodId);
-    sessionManager.updateSessions(eventTime);
+    sessionManager.updateSessions(eventTimeWithTimeline);
 
     ArgumentCaptor<String> sessionId = ArgumentCaptor.forClass(String.class);
-    verify(mockListener).onSessionCreated(eq(eventTime), sessionId.capture());
+    verify(mockListener).onSessionCreated(eq(eventTimeWithTimeline), sessionId.capture());
-    assertThat(sessionManager.belongsToSession(eventTime, sessionId.getValue())).isTrue();
     assertThat(sessionManager.belongsToSession(eventTimeWithTimeline, sessionId.getValue()))
         .isTrue();
     assertThat(sessionManager.belongsToSession(eventTimeWithMediaPeriodId, sessionId.getValue()))
@@ -509,11 +516,11 @@ public final class DefaultPlaybackSessionManagerTest {
 
   @Test
   public void belongsToSession_withOtherWindowIndex_returnsFalse() {
-    EventTime eventTime =
-        createEventTime(Timeline.EMPTY, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
-    EventTime eventTimeOtherWindow =
-        createEventTime(Timeline.EMPTY, /* windowIndex= */ 1, /* mediaPeriodId= */ null);
     Timeline timeline = new FakeTimeline(/* windowCount= */ 2);
+    EventTime eventTime =
+        createEventTime(timeline, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
+    EventTime eventTimeOtherWindow =
+        createEventTime(timeline, /* windowIndex= */ 1, /* mediaPeriodId= */ null);
     MediaPeriodId mediaPeriodId =
         new MediaPeriodId(
             timeline.getUidOfPeriod(/* periodIndex= */ 1), /* windowSequenceNumber= */ 1);
@@ -585,18 +592,18 @@ public final class DefaultPlaybackSessionManagerTest {
   }
 
   @Test
-  public void initialTimelineUpdate_finishesAllSessionsOutsideTimeline() {
+  public void timelineUpdate_toEmpty_finishesAllSessionsAndDoesNotCreateNewSessions() {
+    Timeline timeline = new FakeTimeline(/* windowCount= */ 2);
     EventTime eventTime1 =
-        createEventTime(Timeline.EMPTY, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
+        createEventTime(timeline, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
     EventTime eventTime2 =
-        createEventTime(Timeline.EMPTY, /* windowIndex= */ 1, /* mediaPeriodId= */ null);
+        createEventTime(timeline, /* windowIndex= */ 1, /* mediaPeriodId= */ null);
     sessionManager.updateSessions(eventTime1);
     sessionManager.updateSessions(eventTime2);
-    Timeline timeline = new FakeTimeline();
-    EventTime newTimelineEventTime =
-        createEventTime(timeline, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
 
-    sessionManager.updateSessionsWithTimelineChange(newTimelineEventTime);
+    EventTime eventTimeWithEmptyTimeline =
+        createEventTime(Timeline.EMPTY, /* windowIndex= */ 0, /* mediaPeriodId= */ null);
+    sessionManager.updateSessionsWithTimelineChange(eventTimeWithEmptyTimeline);
 
     ArgumentCaptor<String> sessionId1 = ArgumentCaptor.forClass(String.class);
     ArgumentCaptor<String> sessionId2 = ArgumentCaptor.forClass(String.class);
@@ -605,14 +612,19 @@ public final class DefaultPlaybackSessionManagerTest {
     verify(mockListener).onSessionActive(eventTime1, sessionId1.getValue());
     verify(mockListener)
         .onSessionFinished(
-            newTimelineEventTime,
+            eventTimeWithEmptyTimeline,
+            sessionId1.getValue(),
+            /* automaticTransitionToNextPlayback= */ false);
+    verify(mockListener)
+        .onSessionFinished(
+            eventTimeWithEmptyTimeline,
             sessionId2.getValue(),
             /* automaticTransitionToNextPlayback= */ false);
     verifyNoMoreInteractions(mockListener);
   }
 
   @Test
-  public void dynamicTimelineUpdate_resolvesWindowIndices() {
+  public void timelineUpdate_resolvesWindowIndices() {
     Timeline initialTimeline =
         new FakeTimeline(
             new TimelineWindowDefinition(/* periodCount= */ 2, /* id= */ 100),

library/core/src/test/java/com/google/android/exoplayer2/analytics/PlaybackStatsListenerTest.java

@@ -22,6 +22,7 @@ import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 import androidx.annotation.Nullable;
 import androidx.test.core.app.ApplicationProvider;
@@ -77,15 +78,18 @@ public final class PlaybackStatsListenerTest {
   }
 
   @Test
-  public void stateChangeEvent_toNonIdle_createsInitialPlaybackStats() throws Exception {
+  public void stateChangeEvent_toEndedWithEmptyTimeline_doesNotCreateInitialPlaybackStats()
+      throws Exception {
+    PlaybackStatsListener.Callback callback = mock(PlaybackStatsListener.Callback.class);
     PlaybackStatsListener playbackStatsListener =
-        new PlaybackStatsListener(/* keepHistory= */ true, /* callback= */ null);
+        new PlaybackStatsListener(/* keepHistory= */ true, callback);
     player.addAnalyticsListener(playbackStatsListener);
 
     player.prepare();
     runUntilPendingCommandsAreFullyHandled(player);
 
-    assertThat(playbackStatsListener.getPlaybackStats()).isNotNull();
+    assertThat(playbackStatsListener.getPlaybackStats()).isNull();
+    verifyNoMoreInteractions(callback);
   }
 
   @Test