feat: Add throwOnPreloadNotSupported flag to preload() (#10163)

lib/player.js

@@ -2220,10 +2220,12 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
    *    for VOD and liveEdge for LIVE).
    * @param {?string=} mimeType
    * @param {?shaka.extern.PlayerConfiguration=} config
+   * @param {boolean=} throwOnPreloadNotSupported
    * @return {!Promise<?shaka.media.PreloadManager>}
    * @export
    */
-  async preload(assetUri, startTime = null, mimeType, config) {
+  async preload(assetUri, startTime = null, mimeType, config,
+      throwOnPreloadNotSupported = false) {
     goog.asserts.assert(this.config_, 'Config must not be null!');
     mimeType = mimeType?.toLowerCase();
     const preloadConfig = this.defaultConfig_();
@@ -2233,10 +2235,15 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
         assetUri, startTime, mimeType, /* standardLoad= */ false,
         preloadConfig);
     if (!preloadManager) {
-      this.onError_(new shaka.util.Error(
+      const error = new shaka.util.Error(
           shaka.util.Error.Severity.CRITICAL,
           shaka.util.Error.Category.PLAYER,
-          shaka.util.Error.Code.SRC_EQUALS_PRELOAD_NOT_SUPPORTED));
+          shaka.util.Error.Code.SRC_EQUALS_PRELOAD_NOT_SUPPORTED);
+      if (throwOnPreloadNotSupported) {
+        throw error;
+      } else {
+        this.onError_(error);
+      }
     } else {
       preloadManager.start();
     }

lib/queue/queue_manager.js

@@ -282,7 +282,8 @@ shaka.queue.QueueManager = class extends shaka.util.FakeEventTarget {
         try {
           const preloadManager = await this.player_.preload(
               nextItem.manifestUri, nextItem.startTime,
-              nextItem.mimeType, nextItem.config);
+              nextItem.mimeType, nextItem.config,
+              /* throwOnPreloadNotSupported= */ true);
           this.preloadNext_ = {item: nextItem, preloadManager};
         } catch (e) {
           // Ignore errors during preload

test/queue/queue_manager_unit.js

@@ -162,7 +162,7 @@ describe('QueueManager', () => {
     await shaka.test.Util.shortDelay();
 
     expect(preloadSpy).toHaveBeenCalledWith(
-        queueItem2.manifestUri, null, null, null);
+        queueItem2.manifestUri, null, null, null, true);
   });
 
   it('cleans up previous preload when playing next item', async () => {