Ensure that ShuffleOrder has the same length as the current playlist

Add a fail-fast check in `ExoPlayerImpl` to ensure the equality of the lengths of `ShuffleOrder` and the current playlist. Also improve the documentation of `setShuffleOrder(ShuffleOrder)` with explicit instruction on this.

Issue: androidx/media#480

#minor-release

PiperOrigin-RevId: 544009359
(cherry picked from commit 9cabbc9badbc9301f5e13398b8444377c4e72543)

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayer.java

@@ -1409,6 +1409,9 @@ public interface ExoPlayer extends Player {
   /**
   /**
    * Sets the shuffle order.
    * Sets the shuffle order.
    *
    *
+   * <p>The {@link ShuffleOrder} passed must have the same length as the current playlist ({@link
+   * Player#getMediaItemCount()}).
+   *
    * @param shuffleOrder The shuffle order.
    * @param shuffleOrder The shuffle order.
    */
    */
   void setShuffleOrder(ShuffleOrder shuffleOrder);
   void setShuffleOrder(ShuffleOrder shuffleOrder);

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java

@@ -762,6 +762,7 @@ import java.util.concurrent.TimeoutException;
   @Override
   @Override
   public void setShuffleOrder(ShuffleOrder shuffleOrder) {
   public void setShuffleOrder(ShuffleOrder shuffleOrder) {
     verifyApplicationThread();
     verifyApplicationThread();
+    checkArgument(shuffleOrder.getLength() == mediaSourceHolderSnapshots.size());
     this.shuffleOrder = shuffleOrder;
     this.shuffleOrder = shuffleOrder;
     Timeline timeline = createMaskingTimeline();
     Timeline timeline = createMaskingTimeline();
     PlaybackInfo newPlaybackInfo =
     PlaybackInfo newPlaybackInfo =

library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java

@@ -6946,6 +6946,15 @@ public final class ExoPlayerTest {
   }
   }
 
 
   @Test
   @Test
+  public void setShuffleOrder_shuffleOrderLengthNotEqualToCurrentPlaylistLength_shouldThrow() {
+    ExoPlayer player = new TestExoPlayerBuilder(context).build();
+    player.addMediaSources(ImmutableList.of(new FakeMediaSource(), new FakeMediaSource()));
+
+    assertThrows(
+        IllegalArgumentException.class, () -> player.setShuffleOrder(new FakeShuffleOrder(3)));
+  }
+
+  @Test
   public void setMediaSources_empty_whenEmpty_correctMaskingMediaItemIndex() throws Exception {
   public void setMediaSources_empty_whenEmpty_correctMaskingMediaItemIndex() throws Exception {
     final int[] currentMediaItemIndices = {C.INDEX_UNSET, C.INDEX_UNSET, C.INDEX_UNSET};
     final int[] currentMediaItemIndices = {C.INDEX_UNSET, C.INDEX_UNSET, C.INDEX_UNSET};
     ActionSchedule actionSchedule =
     ActionSchedule actionSchedule =