Class PendingTasks

packages/core/src/pending_tasks.ts:42–92

 * @publicApi 20.0
 */
export class PendingTasks {
  private readonly internalPendingTasks = inject(PendingTasksInternal);
  private readonly scheduler = inject(ChangeDetectionScheduler);
  private readonly errorHandler = inject(INTERNAL_APPLICATION_ERROR_HANDLER);
  /**
   * Adds a new task that should block application's stability.
   * @returns A cleanup function that removes a task when called.
   */
  add(): () => void {
    const taskId = this.internalPendingTasks.add();
    return () => {
      if (!this.internalPendingTasks.has(taskId)) {
        // This pending task has already been cleared.
        return;
      }
      // Notifying the scheduler will hold application stability open until the next tick.
      this.scheduler.notify(NotificationSource.PendingTaskRemoved);
      this.internalPendingTasks.remove(taskId);
    };
  }

  /**
   * Runs an asynchronous function and blocks the application's stability until the function completes.
   *
   * ```ts
   * pendingTasks.run(async () => {
   *   const userData = await fetch('/api/user');
   *   this.userData.set(userData);
   * });
   * ```
   *
   * @param fn The asynchronous function to execute
   * @developerPreview 19.0
   */
  run(fn: () => Promise<unknown>): void {
    const removeTask = this.add();
    try {
      fn().catch(this.errorHandler).finally(removeTask);
    } catch (err) {
      this.errorHandler(err);
      removeTask();
    }
  }

  /** @nocollapse */
  static ɵprov = /** @pureOrBreakMyCode */ /* @__PURE__ */ ɵɵdefineInjectable({
    token: PendingTasks,
    providedIn: 'root',
    factory: () => new PendingTasks(),
  });
}