puppeteer-core/node6/lib/Tracing.js

A high-level API to control headless Chrome over the DevTools Protocol

/**
 * Copyright 2017 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.
 */
const {helper, assert} = require('./helper');
const fs = require('fs');

const openAsync = helper.promisify(fs.open);
const writeAsync = helper.promisify(fs.write);
const closeAsync = helper.promisify(fs.close);

class Tracing {
  /**
   * @param {!Puppeteer.CDPSession} client
   */
  constructor(client) {
    this._client = client;
    this._recording = false;
    this._path = '';
  }

  /**
   * @param {!{path: string, screenshots?: boolean, categories?: !Array<string>}} options
   */
  /* async */ start(options) {return (fn => {
  const gen = fn.call(this);
  return new Promise((resolve, reject) => {
    function step(key, arg) {
      let info, value;
      try {
        info = gen[key](arg);
        value = info.value;
      } catch (error) {
        reject(error);
        return;
      }
      if (info.done) {
        resolve(value);
      } else {
        return Promise.resolve(value).then(
            value => {
              step('next', value);
            },
            err => {
              step('throw', err);
            });
      }
    }
    return step('next');
  });
})(function*(){
    assert(!this._recording, 'Cannot start recording trace while already recording trace.');

    const defaultCategories = [
      '-*', 'devtools.timeline', 'v8.execute', 'disabled-by-default-devtools.timeline',
      'disabled-by-default-devtools.timeline.frame', 'toplevel',
      'blink.console', 'blink.user_timing', 'latencyInfo', 'disabled-by-default-devtools.timeline.stack',
      'disabled-by-default-v8.cpu_profiler', 'disabled-by-default-v8.cpu_profiler.hires'
    ];
    const {
      path = null,
      screenshots = false,
      categories = defaultCategories,
    } = options;

    if (screenshots)
      categories.push('disabled-by-default-devtools.screenshot');

    this._path = path;
    this._recording = true;
    (yield this._client.send('Tracing.start', {
      transferMode: 'ReturnAsStream',
      categories: categories.join(',')
    }));
  });}

  /**
   * @return {!Promise<!Buffer>}
   */
  /* async */ stop() {return (fn => {
  const gen = fn.call(this);
  return new Promise((resolve, reject) => {
    function step(key, arg) {
      let info, value;
      try {
        info = gen[key](arg);
        value = info.value;
      } catch (error) {
        reject(error);
        return;
      }
      if (info.done) {
        resolve(value);
      } else {
        return Promise.resolve(value).then(
            value => {
              step('next', value);
            },
            err => {
              step('throw', err);
            });
      }
    }
    return step('next');
  });
})(function*(){
    let fulfill;
    const contentPromise = new Promise(x => fulfill = x);
    this._client.once('Tracing.tracingComplete', event => {
      this._readStream(event.stream, this._path).then(fulfill);
    });
    (yield this._client.send('Tracing.end'));
    this._recording = false;
    return contentPromise;
  });}

  /**
   * @param {string} handle
   * @param {string} path
   */
  /* async */ _readStream(handle, path) {return (fn => {
  const gen = fn.call(this);
  return new Promise((resolve, reject) => {
    function step(key, arg) {
      let info, value;
      try {
        info = gen[key](arg);
        value = info.value;
      } catch (error) {
        reject(error);
        return;
      }
      if (info.done) {
        resolve(value);
      } else {
        return Promise.resolve(value).then(
            value => {
              step('next', value);
            },
            err => {
              step('throw', err);
            });
      }
    }
    return step('next');
  });
})(function*(){
    let eof = false;
    let file;
    if (path)
      file = (yield openAsync(path, 'w'));
    const bufs = [];
    while (!eof) {
      const response = (yield this._client.send('IO.read', {handle}));
      eof = response.eof;
      bufs.push(Buffer.from(response.data));
      if (path)
        (yield writeAsync(file, response.data));
    }
    if (path)
      (yield closeAsync(file));
    (yield this._client.send('IO.close', {handle}));
    let resultBuffer = null;
    try {
      resultBuffer = Buffer.concat(bufs);
    } finally {
      return resultBuffer;
    }
  });}
}

module.exports = Tracing;