Add non-null by default to source package (last one!)

Note on UnknownNull: Where there exists a generically typed
base class and both null and non-null types are permitted,
we need to clear the default non-null that's otherwise
propagated everywhere. This then lets the nullness of the
type work properly.

PiperOrigin-RevId: 295582444

library/common/src/main/java/com/google/android/exoplayer2/util/UnknownNull.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.util;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import javax.annotation.Nonnull;
+import javax.annotation.meta.TypeQualifierDefault;
+import javax.annotation.meta.When;
+
+/**
+ * Annotation for specifiying unknown nullness. Useful for clearing the effects of an automatically
+ * propagated {@link Nonnull} annotation.
+ */
+@Nonnull(when = When.UNKNOWN)
+@TypeQualifierDefault(ElementType.TYPE_USE)
+@Retention(RetentionPolicy.CLASS)
+public @interface UnknownNull {}

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

@@ -21,6 +21,7 @@ import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.upstream.TransferListener;
 import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.util.UnknownNull;
 import com.google.android.exoplayer2.util.Util;
 import java.io.IOException;
 import java.util.HashMap;
@@ -91,7 +92,7 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    * @param timeline The timeline of the child source.
    */
   protected abstract void onChildSourceInfoRefreshed(
-      T id, MediaSource mediaSource, Timeline timeline);
+      @UnknownNull T id, MediaSource mediaSource, Timeline timeline);
 
   /**
    * Prepares a child source.
@@ -105,7 +106,7 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    * @param id A unique id to identify the child source preparation. Null is allowed as an id.
    * @param mediaSource The child {@link MediaSource}.
    */
-  protected final void prepareChildSource(final T id, MediaSource mediaSource) {
+  protected final void prepareChildSource(@UnknownNull T id, MediaSource mediaSource) {
     Assertions.checkArgument(!childSources.containsKey(id));
     MediaSourceCaller caller =
         (source, timeline) -> onChildSourceInfoRefreshed(id, source, timeline);
@@ -123,7 +124,7 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    *
    * @param id The unique id used to prepare the child source.
    */
-  protected final void enableChildSource(final T id) {
+  protected final void enableChildSource(@UnknownNull T id) {
     MediaSourceAndListener enabledChild = Assertions.checkNotNull(childSources.get(id));
     enabledChild.mediaSource.enable(enabledChild.caller);
   }
@@ -133,7 +134,7 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    *
    * @param id The unique id used to prepare the child source.
    */
-  protected final void disableChildSource(final T id) {
+  protected final void disableChildSource(@UnknownNull T id) {
     MediaSourceAndListener disabledChild = Assertions.checkNotNull(childSources.get(id));
     disabledChild.mediaSource.disable(disabledChild.caller);
   }
@@ -143,7 +144,7 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    *
    * @param id The unique id used to prepare the child source.
    */
-  protected final void releaseChildSource(T id) {
+  protected final void releaseChildSource(@UnknownNull T id) {
     MediaSourceAndListener removedChild = Assertions.checkNotNull(childSources.remove(id));
     removedChild.mediaSource.releaseSource(removedChild.caller);
     removedChild.mediaSource.removeEventListener(removedChild.eventListener);
@@ -157,7 +158,7 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    * @param windowIndex A window index of the child source.
    * @return The corresponding window index in the composite source.
    */
-  protected int getWindowIndexForChildWindowIndex(T id, int windowIndex) {
+  protected int getWindowIndexForChildWindowIndex(@UnknownNull T id, int windowIndex) {
     return windowIndex;
   }
 
@@ -171,8 +172,9 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    * @return The corresponding {@link MediaPeriodId} in the composite source. Null if no
    *     corresponding media period id can be determined.
    */
-  protected @Nullable MediaPeriodId getMediaPeriodIdForChildMediaPeriodId(
+  @Nullable
-      T id, MediaPeriodId mediaPeriodId) {
+  protected MediaPeriodId getMediaPeriodIdForChildMediaPeriodId(
+      @UnknownNull T id, MediaPeriodId mediaPeriodId) {
     return mediaPeriodId;
   }
 
@@ -184,7 +186,7 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
    * @param mediaTimeMs A media time of the child source, in milliseconds.
    * @return The corresponding media time in the composite source, in milliseconds.
    */
-  protected long getMediaTimeForChildMediaTime(@Nullable T id, long mediaTimeMs) {
+  protected long getMediaTimeForChildMediaTime(@UnknownNull T id, long mediaTimeMs) {
     return mediaTimeMs;
   }
 
@@ -216,10 +218,10 @@ public abstract class CompositeMediaSource<T> extends BaseMediaSource {
 
   private final class ForwardingEventListener implements MediaSourceEventListener {
 
-    private final T id;
+    @UnknownNull private final T id;
     private EventDispatcher eventDispatcher;
 
-    public ForwardingEventListener(T id) {
+    public ForwardingEventListener(@UnknownNull T id) {
       this.eventDispatcher = createEventDispatcher(/* mediaPeriodId= */ null);
       this.id = id;
     }

library/core/src/main/java/com/google/android/exoplayer2/source/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.source;
+
+import com.google.android.exoplayer2.util.NonNullApi;