Fix missing notification of session release

A session may not notify its release back to the controller
when the controller is connecting while the session is releasing.
Here are issues in detail:
  - MediaSession doesn't respond to controller's connection
    request when it's released.
  - MediaSession discards incoming connection requests when it's
    released. The requests are only kept in the application
    looper, but the looper is cleared when the session is
    released.

This CL fixes the above issues, and fixes some flaky tests.

PiperOrigin-RevId: 419756158

libraries/session/src/main/java/androidx/media3/session/MediaSessionImpl.java

@@ -313,7 +313,7 @@ import org.checkerframework.checker.initialization.qual.Initialized;
     if (broadcastReceiver != null) {
       context.unregisterReceiver(broadcastReceiver);
     }
-    dispatchRemoteControllerTaskWithoutReturn(ControllerCb::onDisconnected);
+    sessionStub.release();
   }
 
   public PlayerWrapper getPlayerWrapper() {
@@ -604,7 +604,10 @@ import org.checkerframework.checker.initialization.qual.Initialized;
         // 0 is OK for legacy controllers, because they didn't have sequence numbers.
         seq = 0;
       }
-      task.run(checkStateNotNull(controller.getControllerCb()), seq);
+      ControllerCb cb = controller.getControllerCb();
+      if (cb != null) {
+        task.run(cb, seq);
+      }
     } catch (DeadObjectException e) {
       onDeadObjectException(controller, e);
     } catch (RemoteException e) {
@@ -637,7 +640,10 @@ import org.checkerframework.checker.initialization.qual.Initialized;
         // Tell that operation is successful, although we don't know the actual result.
         future = Futures.immediateFuture(new SessionResult(SessionResult.RESULT_SUCCESS));
       }
-      task.run(checkStateNotNull(controller.getControllerCb()), seq);
+      ControllerCb cb = controller.getControllerCb();
+      if (cb != null) {
+        task.run(cb, seq);
+      }
       return future;
     } catch (DeadObjectException e) {
       onDeadObjectException(controller, e);

libraries/session/src/main/java/androidx/media3/session/MediaSessionStub.java

@@ -81,9 +81,12 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.MoreExecutors;
 import java.lang.ref.WeakReference;
+import java.util.Collections;
 import java.util.Deque;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.CancellationException;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 
 /**
@@ -96,19 +99,17 @@ import java.util.concurrent.ExecutionException;
 
   private static final String TAG = "MediaSessionStub";
 
-  private final Object lock;
   private final WeakReference<MediaSessionImpl> sessionImpl;
   private final MediaSessionManager sessionManager;
   private final ConnectedControllersManager<IBinder> connectedControllersManager;
+  private final Set<ControllerInfo> pendingControllers;
 
   public MediaSessionStub(MediaSessionImpl sessionImpl) {
-    // Initialize default values.
-    lock = new Object();
-
     // Initialize members with params.
     this.sessionImpl = new WeakReference<>(sessionImpl);
     sessionManager = MediaSessionManager.getSessionManager(sessionImpl.getContext());
     connectedControllersManager = new ConnectedControllersManager<>(sessionImpl);
+    pendingControllers = Collections.newSetFromMap(new ConcurrentHashMap<>());
   }
 
   public ConnectedControllersManager<IBinder> getConnectedControllersManager() {
@@ -331,11 +332,21 @@ import java.util.concurrent.ExecutionException;
             connectionHints);
     @Nullable MediaSessionImpl sessionImpl = this.sessionImpl.get();
     if (sessionImpl == null || sessionImpl.isReleased()) {
+      try {
+        caller.onDisconnected(/* seq= */ 0);
+      } catch (RemoteException e) {
+        // Controller may be died prematurely.
+        // Not an issue because we'll ignore it anyway.
+      }
       return;
     }
+    pendingControllers.add(controllerInfo);
     postOrRun(
         sessionImpl.getApplicationHandler(),
         () -> {
+          boolean connected = false;
+          try {
+            pendingControllers.remove(controllerInfo);
             if (sessionImpl.isReleased()) {
               return;
             }
@@ -347,17 +358,16 @@ import java.util.concurrent.ExecutionException;
             // Don't reject connection for the request from trusted app.
             // Otherwise server will fail to retrieve session's information to dispatch
             // media keys to.
-          boolean accept = connectionResult.isAccepted || controllerInfo.isTrusted();
+            if (!connectionResult.isAccepted && !controllerInfo.isTrusted()) {
-          if (accept) {
+              return;
+            }
             if (!connectionResult.isAccepted) {
-              // For trusted apps, send non-null allowed commands to keep
+              // For the accepted controller, send non-null allowed commands to keep connection.
-              // connection.
               connectionResult =
                   MediaSession.ConnectionResult.accept(
                       SessionCommands.EMPTY, Player.Commands.EMPTY);
             }
             SequencedFutureManager sequencedFutureManager;
-            synchronized (lock) {
             if (connectedControllersManager.isConnected(controllerInfo)) {
               Log.w(
                   TAG,
@@ -374,7 +384,6 @@ import java.util.concurrent.ExecutionException;
             sequencedFutureManager =
                 checkStateNotNull(
                     connectedControllersManager.getSequencedFutureManager(controllerInfo));
-            }
             // If connection is accepted, notify the current state to the controller.
             // It's needed because we cannot call synchronous calls between
             // session/controller.
@@ -399,22 +408,48 @@ import java.util.concurrent.ExecutionException;
             try {
               caller.onConnected(
                   sequencedFutureManager.obtainNextSequenceNumber(), state.toBundle());
+              connected = true;
             } catch (RemoteException e) {
               // Controller may be died prematurely.
             }
-
             sessionImpl.onPostConnectOnHandler(controllerInfo);
-          } else {
+          } finally {
+            if (!connected) {
               try {
-              caller.onDisconnected(0);
+                caller.onDisconnected(/* seq= */ 0);
               } catch (RemoteException e) {
                 // Controller may be died prematurely.
                 // Not an issue because we'll ignore it anyway.
               }
             }
+          }
         });
   }
 
+  public void release() {
+    List<ControllerInfo> controllers = connectedControllersManager.getConnectedControllers();
+    for (ControllerInfo controller : controllers) {
+      ControllerCb cb = controller.getControllerCb();
+      if (cb != null) {
+        try {
+          cb.onDisconnected(/* seq= */ 0);
+        } catch (RemoteException e) {
+          // Ignore. We're releasing.
+        }
+      }
+    }
+    for (ControllerInfo controller : pendingControllers) {
+      ControllerCb cb = controller.getControllerCb();
+      if (cb != null) {
+        try {
+          cb.onDisconnected(/* seq= */ 0);
+        } catch (RemoteException e) {
+          // Ignore. We're releasing.
+        }
+      }
+    }
+  }
+
   //////////////////////////////////////////////////////////////////////////////////////////////
   // AIDL methods for session overrides
   //////////////////////////////////////////////////////////////////////////////////////////////

libraries/test_session_current/src/androidTest/java/androidx/media3/session/MediaControllerListenerTest.java

@@ -83,6 +83,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;
 import org.junit.After;
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.ClassRule;
 import org.junit.Rule;
@@ -172,6 +173,21 @@ public class MediaControllerListenerTest {
     assertThat(controller).isNotNull();
   }
 
+  @Test
+  public void connection_toReleasedSession() throws Exception {
+    CountDownLatch latch = new CountDownLatch(1);
+    SessionToken token = remoteSession.getToken();
+    remoteSession.release();
+    ListenableFuture<MediaController> controllerFuture =
+        new MediaController.Builder(context, token)
+            .setApplicationLooper(threadTestRule.getHandler().getLooper())
+            .buildAsync();
+    controllerFuture.addListener(() -> latch.countDown(), threadTestRule.getHandler()::post);
+    latch.await(TIMEOUT_MS, MILLISECONDS);
+    Assert.assertThrows(
+        ExecutionException.class, () -> controllerFuture.get(/* timeout= */ 0, MILLISECONDS));
+  }
+
   @Test
   public void connection_sessionReleased() throws Exception {
     CountDownLatch latch = new CountDownLatch(1);

libraries/test_session_current/src/androidTest/java/androidx/media3/session/MediaSessionAndControllerTest.java

@@ -22,14 +22,21 @@ import static com.google.common.truth.Truth.assertThat;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 
 import android.content.Context;
+import android.os.Handler;
 import android.os.Looper;
 import androidx.media3.common.Player;
+import androidx.media3.common.util.Util;
 import androidx.media3.test.session.common.HandlerThreadTestRule;
 import androidx.media3.test.session.common.MainLooperTestRule;
 import androidx.test.core.app.ApplicationProvider;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import androidx.test.filters.LargeTest;
+import com.google.common.util.concurrent.ListenableFuture;
+import java.util.concurrent.CancellationException;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executor;
+import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import org.junit.Before;
 import org.junit.ClassRule;
@@ -100,6 +107,53 @@ public class MediaSessionAndControllerTest {
             });
   }
 
+  /** Tests to ensure that disconnection is notified. */
+  @Test
+  public void connecting_whileSessionIsReleasing_notified() throws Exception {
+    MockPlayer player =
+        new MockPlayer.Builder()
+            .setApplicationLooper(threadTestRule.getHandler().getLooper())
+            .build();
+    Handler mainHandler = new Handler(Looper.getMainLooper());
+    Executor mainExecutor = (runnable) -> Util.postOrRun(mainHandler, runnable);
+    for (int i = 0; i < 100; i++) {
+      int idx = i;
+      MediaSession session =
+          sessionTestRule.ensureReleaseAfterTest(
+              new MediaSession.Builder(context, player).setId(TAG).build());
+      CountDownLatch latch = new CountDownLatch(1);
+      mainHandler.post(
+          () -> {
+            ListenableFuture<MediaController> controllerFuture =
+                new MediaController.Builder(context, session.getToken())
+                    .setListener(
+                        new MediaController.Listener() {
+                          @Override
+                          public void onDisconnected(MediaController controller) {
+                            latch.countDown();
+                          }
+                        })
+                    .buildAsync();
+            controllerFuture.addListener(
+                () -> {
+                  try {
+                    MediaController controller =
+                        controllerFuture.get(/* timeout=* */ 0, MILLISECONDS);
+                    assertThat(controller).isNotNull();
+                  } catch (ExecutionException
+                      | InterruptedException
+                      | CancellationException
+                      | TimeoutException e) {
+                    latch.countDown();
+                  }
+                },
+                mainExecutor);
+          });
+      threadTestRule.getHandler().postAndSync(session::release);
+      assertThat(latch.await(TIMEOUT_MS, MILLISECONDS)).isTrue();
+    }
+  }
+
   @Test
   public void connect_withTheSameLooper_connectsInTheSameLooperIteration() throws Exception {
     // This may hang if controller cannot be connected immediately in a looper iteration.