puppeteer/src/common/TaskQueue.ts

/**
 * Copyright 2020 Google Inc. All rights reserved.
 *
 * 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.
 */

export class TaskQueue {
  #chain: Promise<void>;

  constructor() {
    this.#chain = Promise.resolve();
  }

  postTask<T>(task: () => Promise<T>): Promise<T> {
    const result = this.#chain.then(task);
    this.#chain = result.then(
      () => {
        return undefined;
      },
      () => {
        return undefined;
      }
    );
    return result;
  }
}