chrome-devtools-frontend/front_end/panels/lighthouse/LighthouseProtocolService.ts

Chrome DevTools UI

// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as i18n from '../../core/i18n/i18n.js';
import type * as ProtocolClient from '../../core/protocol_client/protocol_client.js';
import type * as Platform from '../../core/platform/platform.js';
import * as SDK from '../../core/sdk/sdk.js';

import type * as ReportRenderer from './LighthouseReporterTypes.js';

/**
 * @overview
                                                   ┌────────────┐
                                                   │CDP Backend │
                                                   └────────────┘
                                                        │ ▲
                                                        │ │ parallelConnection
                          ┌┐                            ▼ │                     ┌┐
                          ││   dispatchProtocolMessage     sendProtocolMessage  ││
                          ││                     │          ▲                   ││
          ProtocolService ││                     |          │                   ││
                          ││    sendWithResponse ▼          │                   ││
                          ││              │    send          onWorkerMessage    ││
                          └┘              │    │                 ▲              └┘
          worker boundary - - - - - - - - ┼ - -│- - - - - - - - -│- - - - - - - - - - - -
                          ┌┐              ▼    ▼                 │                    ┌┐
                          ││   onFrontendMessage      notifyFrontendViaWorkerMessage  ││
                          ││                   │       ▲                              ││
                          ││                   ▼       │                              ││
LighthouseWorkerService   ││          Either ConnectionProxy or LegacyPort            ││
                          ││                           │ ▲                            ││
                          ││     ┌─────────────────────┼─┼───────────────────────┐    ││
                          ││     │  Lighthouse    ┌────▼──────┐                  │    ││
                          ││     │                │connection │                  │    ││
                          ││     │                └───────────┘                  │    ││
                          └┘     └───────────────────────────────────────────────┘    └┘

 * All messages traversing the worker boundary are action-wrapped.
 * All messages over the parallelConnection speak pure CDP.
 * All messages within ConnectionProxy/LegacyPort speak pure CDP.
 * The foundational CDP connection is `parallelConnection`.
 * All connections within the worker are not actual ParallelConnection's.
*/

let lastId = 1;

export interface LighthouseRun {
  inspectedURL: Platform.DevToolsPath.UrlString;
  categoryIDs: string[];
  flags: Record<string, Object|undefined>;
}

/**
 * ProtocolService manages a connection between the frontend (Lighthouse panel) and the Lighthouse worker.
 */
export class ProtocolService {
  private targetInfo?: {
    mainSessionId: string,
    mainTargetId: string,
    mainFrameId: string,
  };
  private parallelConnection?: ProtocolClient.InspectorBackend.Connection;
  private lighthouseWorkerPromise?: Promise<Worker>;
  private lighthouseMessageUpdateCallback?: ((arg0: string) => void);

  async attach(): Promise<void> {
    await SDK.TargetManager.TargetManager.instance().suspendAllTargets();
    const mainTarget = SDK.TargetManager.TargetManager.instance().mainTarget();
    if (!mainTarget) {
      throw new Error('Unable to find main target required for Lighthouse');
    }
    const childTargetManager = mainTarget.model(SDK.ChildTargetManager.ChildTargetManager);
    if (!childTargetManager) {
      throw new Error('Unable to find child target manager required for Lighthouse');
    }
    const resourceTreeModel = mainTarget.model(SDK.ResourceTreeModel.ResourceTreeModel);
    if (!resourceTreeModel) {
      throw new Error('Unable to find resource tree model required for Lighthouse');
    }
    const mainFrame = resourceTreeModel.mainFrame;
    if (!mainFrame) {
      throw new Error('Unable to find main frame required for Lighthouse');
    }

    const {connection, sessionId} = await childTargetManager.createParallelConnection(message => {
      if (typeof message === 'string') {
        message = JSON.parse(message);
      }
      this.dispatchProtocolMessage(message);
    });

    this.parallelConnection = connection;
    this.targetInfo = {
      mainTargetId: await childTargetManager.getParentTargetId(),
      mainFrameId: mainFrame.id,
      mainSessionId: sessionId,
    };
  }

  getLocales(): readonly string[] {
    return [i18n.DevToolsLocale.DevToolsLocale.instance().locale];
  }

  async startTimespan(currentLighthouseRun: LighthouseRun): Promise<void> {
    const {inspectedURL, categoryIDs, flags} = currentLighthouseRun;

    if (!this.targetInfo) {
      throw new Error('Unable to get target info required for Lighthouse');
    }

    await this.sendWithResponse('startTimespan', {
      url: inspectedURL,
      categoryIDs,
      flags,
      locales: this.getLocales(),
      target: this.targetInfo,
    });
  }

  async collectLighthouseResults(currentLighthouseRun: LighthouseRun): Promise<ReportRenderer.RunnerResult> {
    const {inspectedURL, categoryIDs, flags} = currentLighthouseRun;

    if (!this.targetInfo) {
      throw new Error('Unable to get target info required for Lighthouse');
    }

    let mode = flags.mode as string;
    if (mode === 'timespan') {
      mode = 'endTimespan';
    }

    return this.sendWithResponse(mode, {
      url: inspectedURL,
      categoryIDs,
      flags,
      locales: this.getLocales(),
      target: this.targetInfo,
    });
  }

  async detach(): Promise<void> {
    const oldLighthouseWorker = this.lighthouseWorkerPromise;
    const oldParallelConnection = this.parallelConnection;

    // When detaching, make sure that we remove the old promises, before we
    // perform any async cleanups. That way, if there is a message coming from
    // lighthouse while we are in the process of cleaning up, we shouldn't deliver
    // them to the backend.
    this.lighthouseWorkerPromise = undefined;
    this.parallelConnection = undefined;

    if (oldLighthouseWorker) {
      (await oldLighthouseWorker).terminate();
    }
    if (oldParallelConnection) {
      await oldParallelConnection.disconnect();
    }
    await SDK.TargetManager.TargetManager.instance().resumeAllTargets();
  }

  registerStatusCallback(callback: (arg0: string) => void): void {
    this.lighthouseMessageUpdateCallback = callback;
  }

  private dispatchProtocolMessage(message: Object): void {
    // A message without a sessionId is the main session of the main target (call it "Main session").
    // A parallel connection and session was made that connects to the same main target (call it "Lighthouse session").
    // Messages from the "Lighthouse session" have a sessionId.
    // Without some care, there is a risk of sending the same events for the same main frame to Lighthouse–the backend
    // will create events for the "Main session" and the "Lighthouse session".
    // The workaround–only send message to Lighthouse if:
    //   * the message has a sessionId (is not for the "Main session")
    //   * the message does not have a sessionId (is for the "Main session"), but only for the Target domain
    //     (to kickstart autoAttach in LH).
    const protocolMessage = message as {
      sessionId?: string,
      method?: string,
    };
    if (protocolMessage.sessionId || (protocolMessage.method && protocolMessage.method.startsWith('Target'))) {
      void this.send('dispatchProtocolMessage', {message: JSON.stringify(message)});
    }
  }

  private initWorker(): Promise<Worker> {
    this.lighthouseWorkerPromise = new Promise<Worker>(resolve => {
      const workerUrl = new URL('../../entrypoints/lighthouse_worker/lighthouse_worker.js', import.meta.url);
      const remoteBaseSearchParam = new URL(self.location.href).searchParams.get('remoteBase');
      if (remoteBaseSearchParam) {
        // Allows Lighthouse worker to fetch remote locale files.
        workerUrl.searchParams.set('remoteBase', remoteBaseSearchParam);
      }
      const worker = new Worker(workerUrl, {type: 'module'});

      worker.addEventListener('message', event => {
        if (event.data === 'workerReady') {
          resolve(worker);
          return;
        }

        this.onWorkerMessage(event);
      });
    });
    return this.lighthouseWorkerPromise;
  }

  private async ensureWorkerExists(): Promise<Worker> {
    let worker: Worker;
    if (!this.lighthouseWorkerPromise) {
      worker = await this.initWorker();
    } else {
      worker = await this.lighthouseWorkerPromise;
    }
    return worker;
  }

  private onWorkerMessage(event: MessageEvent): void {
    const lighthouseMessage = JSON.parse(event.data);

    if (lighthouseMessage.action === 'statusUpdate') {
      if (this.lighthouseMessageUpdateCallback && lighthouseMessage.args && 'message' in lighthouseMessage.args) {
        this.lighthouseMessageUpdateCallback(lighthouseMessage.args.message as string);
      }
    } else if (lighthouseMessage.action === 'sendProtocolMessage') {
      if (lighthouseMessage.args && 'message' in lighthouseMessage.args) {
        this.sendProtocolMessage(lighthouseMessage.args.message as string);
      }
    }
  }

  private sendProtocolMessage(message: string): void {
    if (this.parallelConnection) {
      this.parallelConnection.sendRawMessage(message);
    }
  }

  private async send(action: string, args: {[x: string]: string|string[]|Object} = {}): Promise<void> {
    const worker = await this.ensureWorkerExists();
    const messageId = lastId++;
    worker.postMessage(JSON.stringify({id: messageId, action, args: {...args, id: messageId}}));
  }

  /** sendWithResponse currently only handles the original startLighthouse request and LHR-filled response. */
  private async sendWithResponse(action: string, args: {[x: string]: string|string[]|Object} = {}):
      Promise<ReportRenderer.RunnerResult> {
    const worker = await this.ensureWorkerExists();
    const messageId = lastId++;
    const messageResult = new Promise<ReportRenderer.RunnerResult>(resolve => {
      const workerListener = (event: MessageEvent): void => {
        const lighthouseMessage = JSON.parse(event.data);

        if (lighthouseMessage.id === messageId) {
          worker.removeEventListener('message', workerListener);
          resolve(lighthouseMessage.result);
        }
      };
      worker.addEventListener('message', workerListener);
    });
    worker.postMessage(JSON.stringify({id: messageId, action, args: {...args, id: messageId}}));

    return messageResult;
  }
}