Function triggerResourceLoading

packages/core/src/defer/triggering.ts:169–313

(
  tDetails: TDeferBlockDetails,
  lView: LView,
  tNode: TNode,
)

 * @param lView LView of a host view.
 */
export function triggerResourceLoading(
  tDetails: TDeferBlockDetails,
  lView: LView,
  tNode: TNode,
): Promise<unknown> {
  const injector = lView[INJECTOR];
  const tView = lView[TVIEW];

  if (tDetails.loadingState !== DeferDependenciesLoadingState.NOT_STARTED) {
    // If the loading status is different from initial one, it means that
    // the loading of dependencies is in progress and there is nothing to do
    // in this function. All details can be obtained from the `tDetails` object.
    return tDetails.loadingPromise ?? Promise.resolve();
  }

  const lDetails = getLDeferBlockDetails(lView, tNode);
  const primaryBlockTNode = getPrimaryBlockTNode(tView, tDetails);

  // Switch from NOT_STARTED -> IN_PROGRESS state.
  tDetails.loadingState = DeferDependenciesLoadingState.IN_PROGRESS;

  // Prefetching is triggered, cleanup all registered prefetch triggers.
  invokeTriggerCleanupFns(TriggerType.Prefetch, lDetails);

  let dependenciesFn = tDetails.dependencyResolverFn;

  if (ngDevMode) {
    // Check if dependency function interceptor is configured.
    const deferDependencyInterceptor = injector.get(DEFER_BLOCK_DEPENDENCY_INTERCEPTOR, null, {
      optional: true,
    });

    if (deferDependencyInterceptor) {
      dependenciesFn = deferDependencyInterceptor.intercept(dependenciesFn);
    }
  }

  // Indicate that an application is not stable and has a pending task.
  const removeTask = injector.get(PendingTasks).add();

  // The `dependenciesFn` might be `null` when all dependencies within
  // a given defer block were eagerly referenced elsewhere in a file,
  // thus no dynamic `import()`s were produced.
  if (!dependenciesFn) {
    tDetails.loadingPromise = Promise.resolve().then(() => {
      tDetails.loadingPromise = null;
      tDetails.loadingState = DeferDependenciesLoadingState.COMPLETE;
      removeTask();
    });
    return tDetails.loadingPromise;
  }

  // Start downloading of defer block dependencies.
  tDetails.loadingPromise = Promise.allSettled(dependenciesFn()).then((results) => {
    let failed = false;
    let failedReason: Error | null = null;
    const directiveDefs: DirectiveDefList = [];
    const pipeDefs: PipeDefList = [];