feat(MediaSource): client code can get the tag of a MediaSource

extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsMediaSource.java

@@ -100,6 +100,12 @@ public final class ImaAdsMediaSource extends BaseMediaSource implements SourceIn
     adsMediaSource.releasePeriod(mediaPeriod);
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return adsMediaSource.getTag();
+  }
+
   @Override
   public void releaseSourceInternal() {
     adsMediaSource.releaseSource(/* listener= */ this);

library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java

@@ -224,6 +224,12 @@ public final class ClippingMediaSource extends CompositeMediaSource<Void> {
     }
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return mediaSource.getTag();
+  }
+
   @Override
   public void releaseSourceInternal() {
     super.releaseSourceInternal();

library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java

@@ -508,6 +508,12 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
     maybeReleaseChildSource(holder);
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return null;
+  }
+
   @Override
   public final void releaseSourceInternal() {
     super.releaseSourceInternal();
@@ -1069,6 +1075,12 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
       // Do nothing.
     }
 
+    @Override
+    @Nullable
+    public Object getTag() {
+      return null;
+    }
+
     @Override
     protected void releaseSourceInternal() {
       // Do nothing.

library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java

@@ -395,6 +395,12 @@ public final class ExtractorMediaSource extends BaseMediaSource
     ((ExtractorMediaPeriod) mediaPeriod).release();
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return tag;
+  }
+
   @Override
   public void releaseSourceInternal() {
     // Do nothing.

library/core/src/main/java/com/google/android/exoplayer2/source/LoopingMediaSource.java

@@ -95,6 +95,12 @@ public final class LoopingMediaSource extends CompositeMediaSource<Void> {
     }
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return childSource.getTag();
+  }
+
   @Override
   protected void onChildSourceInfoRefreshed(
       Void id, MediaSource mediaSource, Timeline timeline, @Nullable Object manifest) {

library/core/src/main/java/com/google/android/exoplayer2/source/MediaSource.java

@@ -275,6 +275,11 @@ public interface MediaSource {
    */
   void releasePeriod(MediaPeriod mediaPeriod);
 
+  /**
+   * Returns the tag set on media source, or null when none was set.
+   */
+  Object getTag();
+
   /**
    * Removes a listener for timeline and/or manifest updates and releases the source if no longer
    * required.

library/core/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java

@@ -137,6 +137,12 @@ public final class MergingMediaSource extends CompositeMediaSource<Integer> {
     }
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return mediaSources.length > 0 ? mediaSources[0].getTag() : null;
+  }
+
   @Override
   public void releaseSourceInternal() {
     super.releaseSourceInternal();

library/core/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java

@@ -185,6 +185,7 @@ public final class SingleSampleMediaSource extends BaseMediaSource {
   private final LoadErrorHandlingPolicy loadErrorHandlingPolicy;
   private final boolean treatLoadErrorsAsEndOfStream;
   private final Timeline timeline;
+  private final @Nullable Object tag;
 
   private @Nullable TransferListener transferListener;
 
@@ -287,6 +288,7 @@ public final class SingleSampleMediaSource extends BaseMediaSource {
     this.durationUs = durationUs;
     this.loadErrorHandlingPolicy = loadErrorHandlingPolicy;
     this.treatLoadErrorsAsEndOfStream = treatLoadErrorsAsEndOfStream;
+    this.tag = tag;
     dataSpec =
         new DataSpec(uri, DataSpec.FLAG_ALLOW_GZIP | DataSpec.FLAG_ALLOW_CACHING_UNKNOWN_LENGTH);
     timeline =
@@ -327,6 +329,12 @@ public final class SingleSampleMediaSource extends BaseMediaSource {
     ((SingleSampleMediaPeriod) mediaPeriod).release();
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return tag;
+  }
+
   @Override
   public void releaseSourceInternal() {
     // Do nothing.

library/core/src/main/java/com/google/android/exoplayer2/source/ads/AdsMediaSource.java

@@ -387,6 +387,12 @@ public final class AdsMediaSource extends CompositeMediaSource<MediaPeriodId> {
     deferredMediaPeriod.releasePeriod();
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return contentMediaSource.getTag();
+  }
+
   @Override
   public void releaseSourceInternal() {
     super.releaseSourceInternal();

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java

@@ -658,6 +658,12 @@ public final class DashMediaSource extends BaseMediaSource {
     periodsById.remove(dashMediaPeriod.id);
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return tag;
+  }
+
   @Override
   public void releaseSourceInternal() {
     manifestLoadPending = false;

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java

@@ -425,6 +425,12 @@ public final class HlsMediaSource extends BaseMediaSource
     ((HlsMediaPeriod) mediaPeriod).release();
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return tag;
+  }
+
   @Override
   public void releaseSourceInternal() {
     playlistTracker.stop();

library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java

@@ -549,6 +549,12 @@ public final class SsMediaSource extends BaseMediaSource
     mediaPeriods.remove(period);
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    return tag;
+  }
+
   @Override
   public void releaseSourceInternal() {
     manifest = sideloadedManifest ? manifest : null;

testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeMediaSource.java

@@ -133,6 +133,14 @@ public class FakeMediaSource extends BaseMediaSource {
     fakeMediaPeriod.release();
   }
 
+  @Override
+  @Nullable
+  public Object getTag() {
+    boolean hasTimeline = timeline != null && !timeline.isEmpty();
+
+    return hasTimeline ? timeline.getWindow(0, new Timeline.Window()).tag : null;
+  }
+
   @Override
   public void releaseSourceInternal() {
     assertThat(preparedSource).isTrue();