puppeteer-core/src/api/WebWorker.ts

/**
 * @license
 * Copyright 2018 Google Inc.
 * SPDX-License-Identifier: Apache-2.0
 */

import {UnsupportedOperation} from '../common/Errors.js';
import {EventEmitter, type EventType} from '../common/EventEmitter.js';
import {TimeoutSettings} from '../common/TimeoutSettings.js';
import type {EvaluateFunc, HandleFor} from '../common/types.js';
import {withSourcePuppeteerURLIfNone} from '../common/util.js';

import type {CDPSession} from './CDPSession.js';
import type {Realm} from './Realm.js';

/**
 * This class represents a
 * {@link https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API | WebWorker}.
 *
 * @remarks
 * The events `workercreated` and `workerdestroyed` are emitted on the page
 * object to signal the worker lifecycle.
 *
 * @example
 *
 * ```ts
 * page.on('workercreated', worker =>
 *   console.log('Worker created: ' + worker.url()),
 * );
 * page.on('workerdestroyed', worker =>
 *   console.log('Worker destroyed: ' + worker.url()),
 * );
 *
 * console.log('Current workers:');
 * for (const worker of page.workers()) {
 *   console.log('  ' + worker.url());
 * }
 * ```
 *
 * @public
 */
export abstract class WebWorker extends EventEmitter<
  Record<EventType, unknown>
> {
  /**
   * @internal
   */
  readonly timeoutSettings = new TimeoutSettings();

  readonly #url: string;

  /**
   * @internal
   */
  constructor(url: string) {
    super();

    this.#url = url;
  }

  /**
   * @internal
   */
  abstract mainRealm(): Realm;

  /**
   * The URL of this web worker.
   */
  url(): string {
    return this.#url;
  }

  /**
   * The CDP session client the WebWorker belongs to.
   */
  abstract get client(): CDPSession;

  /**
   * Evaluates a given function in the {@link WebWorker | worker}.
   *
   * @remarks If the given function returns a promise,
   * {@link WebWorker.evaluate | evaluate} will wait for the promise to resolve.
   *
   * As a rule of thumb, if the return value of the given function is more
   * complicated than a JSON object (e.g. most classes), then
   * {@link WebWorker.evaluate | evaluate} will _likely_ return some truncated
   * value (or `{}`). This is because we are not returning the actual return
   * value, but a deserialized version as a result of transferring the return
   * value through a protocol to Puppeteer.
   *
   * In general, you should use
   * {@link WebWorker.evaluateHandle | evaluateHandle} if
   * {@link WebWorker.evaluate | evaluate} cannot serialize the return value
   * properly or you need a mutable {@link JSHandle | handle} to the return
   * object.
   *
   * @param func - Function to be evaluated.
   * @param args - Arguments to pass into `func`.
   * @returns The result of `func`.
   */
  async evaluate<
    Params extends unknown[],
    Func extends EvaluateFunc<Params> = EvaluateFunc<Params>,
  >(func: Func | string, ...args: Params): Promise<Awaited<ReturnType<Func>>> {
    func = withSourcePuppeteerURLIfNone(this.evaluate.name, func);
    return await this.mainRealm().evaluate(func, ...args);
  }

  /**
   * Evaluates a given function in the {@link WebWorker | worker}.
   *
   * @remarks If the given function returns a promise,
   * {@link WebWorker.evaluate | evaluate} will wait for the promise to resolve.
   *
   * In general, you should use
   * {@link WebWorker.evaluateHandle | evaluateHandle} if
   * {@link WebWorker.evaluate | evaluate} cannot serialize the return value
   * properly or you need a mutable {@link JSHandle | handle} to the return
   * object.
   *
   * @param func - Function to be evaluated.
   * @param args - Arguments to pass into `func`.
   * @returns A {@link JSHandle | handle} to the return value of `func`.
   */
  async evaluateHandle<
    Params extends unknown[],
    Func extends EvaluateFunc<Params> = EvaluateFunc<Params>,
  >(
    func: Func | string,
    ...args: Params
  ): Promise<HandleFor<Awaited<ReturnType<Func>>>> {
    func = withSourcePuppeteerURLIfNone(this.evaluateHandle.name, func);
    return await this.mainRealm().evaluateHandle(func, ...args);
  }

  async close(): Promise<void> {
    throw new UnsupportedOperation('WebWorker.close() is not supported');
  }
}