puppeteer/packages/puppeteer-core/src/common/LazyArg.ts

/**
 * Copyright 2022 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.
 */

/**
 * @internal
 */
export class LazyArg<T> {
  static create = <T>(callback: () => Promise<T>): T => {
    // We do type coercion here because we don't want to introduce LazyArgs to
    // the type system.
    return new LazyArg(callback) as unknown as T;
  };

  #get: () => Promise<T>;
  private constructor(get: () => Promise<T>) {
    this.#get = get;
  }

  get(): Promise<T> {
    return this.#get();
  }
}