feat(preload): Add new method destroyAllPreloads (#6756)

Author: theodab

lib/player.js

@@ -934,14 +934,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
     // A PreloadManager can only be used with the Player instance that created
     // it, so all PreloadManagers this Player has created are now useless.
     // Destroy any remaining managers now, to help prevent memory leaks.
-    const preloadManagerDestroys = [];
-    for (const preloadManager of this.createdPreloadManagers_) {
-      if (!preloadManager.isDestroyed()) {
-        preloadManagerDestroys.push(preloadManager.destroy());
-      }
-    }
-    this.createdPreloadManagers_ = [];
-    await Promise.all(preloadManagerDestroys);
+    await this.destroyAllPreloads();
 
     // Tear-down the event managers to ensure handlers stop firing.
     if (this.globalEventManager_) {
@@ -1796,6 +1789,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
           /* allowPrefetch= */ true,
           /* disableVideo= */ false,
           /* allowMakeAbrManager= */ false);
+      this.createdPreloadManagers_.push(preloadManager);
       preloadManager.attachManifest(
           this.manifest_, this.parser_, this.parserFactory_);
       preloadManager.attachAbrManager(
@@ -1853,6 +1847,21 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
     return preloadManager;
   }
 
+  /**
+   * Calls |destroy| on each PreloadManager object this player has created.
+   * @export
+   */
+  async destroyAllPreloads() {
+    const preloadManagerDestroys = [];
+    for (const preloadManager of this.createdPreloadManagers_) {
+      if (!preloadManager.isDestroyed()) {
+        preloadManagerDestroys.push(preloadManager.destroy());
+      }
+    }
+    this.createdPreloadManagers_ = [];
+    await Promise.all(preloadManagerDestroys);
+  }
+
   /**
    * @param {string} assetUri
    * @param {?number} startTime
@@ -1890,9 +1899,21 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
         disableVideo = true;
       }
     }
-    return this.makePreloadManager_(
+    let preloadManagerPromise = this.makePreloadManager_(
         assetUri, startTime, mimeType || null, startTimeOfLoad,
         /* allowPrefetch= */ !standardLoad, disableVideo, allowMakeAbrManager);
+    if (!standardLoad) {
+      // We only need to track the PreloadManager if it is not part of a
+      // standard load. If it is, the load() method will handle destroying it.
+      // Adding a standard load PreloadManager to the createdPreloadManagers_
+      // array runs the risk that the user will call destroyAllPreloads and
+      // destroy that PreloadManager mid-load.
+      preloadManagerPromise = preloadManagerPromise.then((preloadManager) => {
+        this.createdPreloadManagers_.push(preloadManager);
+        return preloadManager;
+      });
+    }
+    return preloadManagerPromise;
   }
 
   /**
@@ -2114,7 +2135,6 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
     };
     preloadManager = new shaka.media.PreloadManager(
         assetUri, mimeType, startTimeOfLoad, startTime, playerInterface);
-    this.createdPreloadManagers_.push(preloadManager);
     return preloadManager;
   }
 

test/cast/cast_utils_unit.js

@@ -31,6 +31,7 @@ describe('CastUtils', () => {
       'detachAndSavePreload',
       'unloadAndSavePreload',
       'preload',
+      'destroyAllPreloads',
       'getNonDefaultConfiguration',
 
       // Test helper methods (not @export'd)