Add getPlaybackError to Player/ExoPlayer interface

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=193400443

RELEASENOTES.md

@@ -9,6 +9,7 @@
 * Updated default max buffer length in `DefaultLoadControl`.
 * Added `AnalyticsListener` interface which can be registered in
   `SimpleExoPlayer` to receive detailed meta data for each ExoPlayer event.
+* Added `getPlaybackError` to `Player` interface.
 * UI components:
   * Add support for listening to `AspectRatioFrameLayout`'s aspect ratio update
     ([#3736](https://github.com/google/ExoPlayer/issues/3736)).

extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastPlayer.java

@@ -307,6 +307,11 @@ public final class CastPlayer implements Player {
     return playbackState;
   }
 
+  @Override
+  public Exception getPlaybackError() {
+    return null;
+  }
+
   @Override
   public void setPlayWhenReady(boolean playWhenReady) {
     if (remoteMediaClient == null) {

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

@@ -185,6 +185,10 @@ public interface ExoPlayer extends Player {
    */
   Looper getPlaybackLooper();
 
+  @Override
+  @Nullable
+  ExoPlaybackException getPlaybackError();
+
   /**
    * Prepares the player to play the provided {@link MediaSource}. Equivalent to
    * {@code prepare(mediaSource, true, true)}.

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

@@ -61,6 +61,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
   private boolean hasPendingPrepare;
   private boolean hasPendingSeek;
   private PlaybackParameters playbackParameters;
+  private @Nullable ExoPlaybackException playbackError;
 
   // Playback information when there is no pending seek/set source operation.
   private PlaybackInfo playbackInfo;
@@ -156,6 +157,11 @@ import java.util.concurrent.CopyOnWriteArraySet;
     return playbackInfo.playbackState;
   }
 
+  @Override
+  public @Nullable ExoPlaybackException getPlaybackError() {
+    return playbackError;
+  }
+
   @Override
   public void prepare(MediaSource mediaSource) {
     prepare(mediaSource, true, true);
@@ -163,6 +169,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public void prepare(MediaSource mediaSource, boolean resetPosition, boolean resetState) {
+    playbackError = null;
     PlaybackInfo playbackInfo =
         getResetPlaybackInfo(
             resetPosition, resetState, /* playbackState= */ Player.STATE_BUFFERING);
@@ -325,6 +332,9 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public void stop(boolean reset) {
+    if (reset) {
+      playbackError = null;
+    }
     PlaybackInfo playbackInfo =
         getResetPlaybackInfo(
             /* resetPosition= */ reset,
@@ -560,9 +570,9 @@ import java.util.concurrent.CopyOnWriteArraySet;
         }
         break;
       case ExoPlayerImplInternal.MSG_ERROR:
-        ExoPlaybackException exception = (ExoPlaybackException) msg.obj;
+        playbackError = (ExoPlaybackException) msg.obj;
         for (Player.EventListener listener : listeners) {
-          listener.onPlayerError(exception);
+          listener.onPlayerError(playbackError);
         }
         break;
       default:

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

@@ -459,6 +459,17 @@ public interface Player {
    */
   int getPlaybackState();
 
+  /**
+   * Returns the error that caused playback to fail. This is the same error that will have been
+   * reported via @link Player.EventListener#onPlayerError(ExoPlaybackException)} at the time of
+   * failure. It can be queried using this method until {@code stop(true)} is called or the player
+   * is re-prepared.
+   *
+   * @return The error, or {@code null}.
+   */
+  @Nullable
+  Exception getPlaybackError();
+
   /**
    * Sets whether playback should proceed when {@link #getPlaybackState()} == {@link #STATE_READY}.
    * <p>

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

@@ -653,6 +653,11 @@ public class SimpleExoPlayer implements ExoPlayer, Player.VideoComponent, Player
     return player.getPlaybackState();
   }
 
+  @Override
+  public ExoPlaybackException getPlaybackError() {
+    return player.getPlaybackError();
+  }
+
   @Override
   public void prepare(MediaSource mediaSource) {
     prepare(mediaSource, /* resetPosition= */ true, /* resetState= */ true);

testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/StubExoPlayer.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.testutil;
 
 import android.os.Looper;
 import android.support.annotation.Nullable;
+import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.ExoPlayer;
 import com.google.android.exoplayer2.PlaybackParameters;
 import com.google.android.exoplayer2.Player;
@@ -63,6 +64,11 @@ public abstract class StubExoPlayer implements ExoPlayer {
     throw new UnsupportedOperationException();
   }
 
+  @Override
+  public ExoPlaybackException getPlaybackError() {
+    throw new UnsupportedOperationException();
+  }
+
   @Override
   public void prepare(MediaSource mediaSource) {
     throw new UnsupportedOperationException();