puppeteer/lib/FrameManager.js

/**
 * 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 fs = require('fs');
const EventEmitter = require('events');
const {helper, assert} = require('./helper');
const {ExecutionContext, JSHandle} = require('./ExecutionContext');
const {ElementHandle} = require('./ElementHandle');
const {TimeoutError} = require('./Errors');

const readFileAsync = helper.promisify(fs.readFile);

class FrameManager extends EventEmitter {
  /**
   * @param {!Puppeteer.CDPSession} client
   * @param {!Protocol.Page.FrameTree} frameTree
   * @param {!Puppeteer.Page} page
   */
  constructor(client, frameTree, page) {
    super();
    this._client = client;
    this._page = page;
    /** @type {!Map<string, !Frame>} */
    this._frames = new Map();
    /** @type {!Map<number, !ExecutionContext>} */
    this._contextIdToContext = new Map();

    this._client.on('Page.frameAttached', event => this._onFrameAttached(event.frameId, event.parentFrameId));
    this._client.on('Page.frameNavigated', event => this._onFrameNavigated(event.frame));
    this._client.on('Page.navigatedWithinDocument', event => this._onFrameNavigatedWithinDocument(event.frameId, event.url));
    this._client.on('Page.frameDetached', event => this._onFrameDetached(event.frameId));
    this._client.on('Page.frameStoppedLoading', event => this._onFrameStoppedLoading(event.frameId));
    this._client.on('Runtime.executionContextCreated', event => this._onExecutionContextCreated(event.context));
    this._client.on('Runtime.executionContextDestroyed', event => this._onExecutionContextDestroyed(event.executionContextId));
    this._client.on('Runtime.executionContextsCleared', event => this._onExecutionContextsCleared());
    this._client.on('Page.lifecycleEvent', event => this._onLifecycleEvent(event));

    this._handleFrameTree(frameTree);
  }

  /**
   * @param {!Protocol.Page.lifecycleEventPayload} event
   */
  _onLifecycleEvent(event) {
    const frame = this._frames.get(event.frameId);
    if (!frame)
      return;
    frame._onLifecycleEvent(event.loaderId, event.name);
    this.emit(FrameManager.Events.LifecycleEvent, frame);
  }

  /**
   * @param {string} frameId
   */
  _onFrameStoppedLoading(frameId) {
    const frame = this._frames.get(frameId);
    if (!frame)
      return;
    frame._onLoadingStopped();
    this.emit(FrameManager.Events.LifecycleEvent, frame);
  }

  /**
   * @param {!Protocol.Page.FrameTree} frameTree
   */
  _handleFrameTree(frameTree) {
    if (frameTree.frame.parentId)
      this._onFrameAttached(frameTree.frame.id, frameTree.frame.parentId);
    this._onFrameNavigated(frameTree.frame);
    if (!frameTree.childFrames)
      return;

    for (const child of frameTree.childFrames)
      this._handleFrameTree(child);
  }

  /**
   * @return {!Frame}
   */
  mainFrame() {
    return this._mainFrame;
  }

  /**
   * @return {!Array<!Frame>}
   */
  frames() {
    return Array.from(this._frames.values());
  }

  /**
   * @param {!string} frameId
   * @return {?Frame}
   */
  frame(frameId) {
    return this._frames.get(frameId) || null;
  }

  /**
   * @param {string} frameId
   * @param {?string} parentFrameId
   * @return {?Frame}
   */
  _onFrameAttached(frameId, parentFrameId) {
    if (this._frames.has(frameId))
      return;
    assert(parentFrameId);
    const parentFrame = this._frames.get(parentFrameId);
    const frame = new Frame(this._client, parentFrame, frameId);
    this._frames.set(frame._id, frame);
    this.emit(FrameManager.Events.FrameAttached, frame);
  }

  /**
   * @param {!Protocol.Page.Frame} framePayload
   */
  _onFrameNavigated(framePayload) {
    const isMainFrame = !framePayload.parentId;
    let frame = isMainFrame ? this._mainFrame : this._frames.get(framePayload.id);
    assert(isMainFrame || frame, 'We either navigate top level or have old version of the navigated frame');

    // Detach all child frames first.
    if (frame) {
      for (const child of frame.childFrames())
        this._removeFramesRecursively(child);
    }

    // Update or create main frame.
    if (isMainFrame) {
      if (frame) {
        // Update frame id to retain frame identity on cross-process navigation.
        this._frames.delete(frame._id);
        frame._id = framePayload.id;
      } else {
        // Initial main frame navigation.
        frame = new Frame(this._client, null, framePayload.id);
      }
      this._frames.set(framePayload.id, frame);
      this._mainFrame = frame;
    }

    // Update frame payload.
    frame._navigated(framePayload);

    this.emit(FrameManager.Events.FrameNavigated, frame);
  }

  /**
   * @param {string} frameId
   * @param {string} url
   */
  _onFrameNavigatedWithinDocument(frameId, url) {
    const frame = this._frames.get(frameId);
    if (!frame)
      return;
    frame._navigatedWithinDocument(url);
    this.emit(FrameManager.Events.FrameNavigatedWithinDocument, frame);
    this.emit(FrameManager.Events.FrameNavigated, frame);
  }

  /**
   * @param {string} frameId
   */
  _onFrameDetached(frameId) {
    const frame = this._frames.get(frameId);
    if (frame)
      this._removeFramesRecursively(frame);
  }

  _onExecutionContextCreated(contextPayload) {
    const frameId = contextPayload.auxData ? contextPayload.auxData.frameId : null;
    const frame = this._frames.get(frameId) || null;
    /** @type {!ExecutionContext} */
    const context = new ExecutionContext(this._client, contextPayload, obj => this.createJSHandle(context, obj), frame);
    this._contextIdToContext.set(contextPayload.id, context);
    if (frame)
      frame._addExecutionContext(context);
  }

  /**
   * @param {number} executionContextId
   */
  _onExecutionContextDestroyed(executionContextId) {
    const context = this._contextIdToContext.get(executionContextId);
    if (!context)
      return;
    this._contextIdToContext.delete(executionContextId);
    if (context.frame())
      context.frame()._removeExecutionContext(context);
  }

  _onExecutionContextsCleared() {
    for (const context of this._contextIdToContext.values()) {
      if (context.frame())
        context.frame()._removeExecutionContext(context);
    }
    this._contextIdToContext.clear();
  }

  /**
   * @param {number} contextId
   * @return {!ExecutionContext}
   */
  executionContextById(contextId) {
    const context = this._contextIdToContext.get(contextId);
    assert(context, 'INTERNAL ERROR: missing context with id = ' + contextId);
    return context;
  }

  /**
   * @param {!ExecutionContext} context
   * @param {!Protocol.Runtime.RemoteObject} remoteObject
   * @return {!JSHandle}
   */
  createJSHandle(context, remoteObject) {
    if (remoteObject.subtype === 'node')
      return new ElementHandle(context, this._client, remoteObject, this._page, this);
    return new JSHandle(context, this._client, remoteObject);
  }

  /**
   * @param {!Frame} frame
   */
  _removeFramesRecursively(frame) {
    for (const child of frame.childFrames())
      this._removeFramesRecursively(child);
    frame._detach();
    this._frames.delete(frame._id);
    this.emit(FrameManager.Events.FrameDetached, frame);
  }
}

/** @enum {string} */
FrameManager.Events = {
  FrameAttached: 'frameattached',
  FrameNavigated: 'framenavigated',
  FrameDetached: 'framedetached',
  LifecycleEvent: 'lifecycleevent',
  FrameNavigatedWithinDocument: 'framenavigatedwithindocument',
  ExecutionContextCreated: 'executioncontextcreated',
  ExecutionContextDestroyed: 'executioncontextdestroyed',
};

/**
 * @unrestricted
 */
class Frame {
  /**
   * @param {!Puppeteer.CDPSession} client
   * @param {?Frame} parentFrame
   * @param {string} frameId
   */
  constructor(client, parentFrame, frameId) {
    this._client = client;
    this._parentFrame = parentFrame;
    this._url = '';
    this._id = frameId;

    /** @type {?Promise<!ElementHandle>} */
    this._documentPromise = null;
    /** @type {?Promise<!ExecutionContext>} */
    this._contextPromise = null;
    this._contextResolveCallback = null;
    this._setDefaultContext(null);

    /** @type {!Set<!WaitTask>} */
    this._waitTasks = new Set();
    this._loaderId = '';
    /** @type {!Set<string>} */
    this._lifecycleEvents = new Set();

    /** @type {!Set<!Frame>} */
    this._childFrames = new Set();
    if (this._parentFrame)
      this._parentFrame._childFrames.add(this);
  }

  /**
   * @param {!ExecutionContext} context
   */
  _addExecutionContext(context) {
    if (context._isDefault)
      this._setDefaultContext(context);
  }

  /**
   * @param {!ExecutionContext} context
   */
  _removeExecutionContext(context) {
    if (context._isDefault)
      this._setDefaultContext(null);
  }

  /**
   * @param {?ExecutionContext} context
   */
  _setDefaultContext(context) {
    if (context) {
      this._contextResolveCallback.call(null, context);
      this._contextResolveCallback = null;
      for (const waitTask of this._waitTasks)
        waitTask.rerun();
    } else {
      this._documentPromise = null;
      this._contextPromise = new Promise(fulfill => {
        this._contextResolveCallback = fulfill;
      });
    }
  }

  /**
   * @return {!Promise<!ExecutionContext>}
   */
  executionContext() {
    return this._contextPromise;
  }

  /**
   * @param {function()|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<!Puppeteer.JSHandle>}
   */
  async evaluateHandle(pageFunction, ...args) {
    const context = await this._contextPromise;
    return context.evaluateHandle(pageFunction, ...args);
  }

  /**
   * @param {Function|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<*>}
   */
  async evaluate(pageFunction, ...args) {
    const context = await this._contextPromise;
    return context.evaluate(pageFunction, ...args);
  }

  /**
   * @param {string} selector
   * @return {!Promise<?ElementHandle>}
   */
  async $(selector) {
    const document = await this._document();
    const value = await document.$(selector);
    return value;
  }

  /**
   * @return {!Promise<!ElementHandle>}
   */
  async _document() {
    if (this._documentPromise)
      return this._documentPromise;
    this._documentPromise = this._contextPromise.then(async context => {
      const document = await context.evaluateHandle('document');
      return document.asElement();
    });
    return this._documentPromise;
  }

  /**
   * @param {string} expression
   * @return {!Promise<!Array<!ElementHandle>>}
   */
  async $x(expression) {
    const document = await this._document();
    const value = await document.$x(expression);
    return value;
  }

  /**
   * @param {string} selector
   * @param {Function|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<(!Object|undefined)>}
   */
  async $eval(selector, pageFunction, ...args) {
    const document = await this._document();
    return document.$eval(selector, pageFunction, ...args);
  }

  /**
   * @param {string} selector
   * @param {Function|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<(!Object|undefined)>}
   */
  async $$eval(selector, pageFunction, ...args) {
    const document = await this._document();
    const value = await document.$$eval(selector, pageFunction, ...args);
    return value;
  }

  /**
   * @param {string} selector
   * @return {!Promise<!Array<!ElementHandle>>}
   */
  async $$(selector) {
    const document = await this._document();
    const value = await document.$$(selector);
    return value;
  }

  /**
   * @return {!Promise<String>}
   */
  async content() {
    return await this.evaluate(() => {
      let retVal = '';
      if (document.doctype)
        retVal = new XMLSerializer().serializeToString(document.doctype);
      if (document.documentElement)
        retVal += document.documentElement.outerHTML;
      return retVal;
    });
  }

  /**
   * @param {string} html
   */
  async setContent(html) {
    await this.evaluate(html => {
      document.open();
      document.write(html);
      document.close();
    }, html);
  }

  /**
   * @return {string}
   */
  name() {
    return this._name || '';
  }

  /**
   * @return {string}
   */
  url() {
    return this._url;
  }

  /**
   * @return {?Frame}
   */
  parentFrame() {
    return this._parentFrame;
  }

  /**
   * @return {!Array.<!Frame>}
   */
  childFrames() {
    return Array.from(this._childFrames);
  }

  /**
   * @return {boolean}
   */
  isDetached() {
    return this._detached;
  }

  /**
   * @param {Object} options
   * @return {!Promise<!ElementHandle>}
   */
  async addScriptTag(options) {
    if (typeof options.url === 'string') {
      const url = options.url;
      try {
        const context = await this._contextPromise;
        return (await context.evaluateHandle(addScriptUrl, url, options.type)).asElement();
      } catch (error) {
        throw new Error(`Loading script from ${url} failed`);
      }
    }

    if (typeof options.path === 'string') {
      let contents = await readFileAsync(options.path, 'utf8');
      contents += '//# sourceURL=' + options.path.replace(/\n/g, '');
      const context = await this._contextPromise;
      return (await context.evaluateHandle(addScriptContent, contents, options.type)).asElement();
    }

    if (typeof options.content === 'string') {
      const context = await this._contextPromise;
      return (await context.evaluateHandle(addScriptContent, options.content, options.type)).asElement();
    }

    throw new Error('Provide an object with a `url`, `path` or `content` property');

    /**
     * @param {string} url
     * @param {string} type
     * @return {!Promise<!HTMLElement>}
     */
    async function addScriptUrl(url, type) {
      const script = document.createElement('script');
      script.src = url;
      if (type)
        script.type = type;
      const promise = new Promise((res, rej) => {
        script.onload = res;
        script.onerror = rej;
      });
      document.head.appendChild(script);
      await promise;
      return script;
    }

    /**
     * @param {string} content
     * @param {string} type
     * @return {!HTMLElement}
     */
    function addScriptContent(content, type = 'text/javascript') {
      const script = document.createElement('script');
      script.type = type;
      script.text = content;
      let error = null;
      script.onerror = e => error = e;
      document.head.appendChild(script);
      if (error)
        throw error;
      return script;
    }
  }

  /**
   * @param {Object} options
   * @return {!Promise<!ElementHandle>}
   */
  async addStyleTag(options) {
    if (typeof options.url === 'string') {
      const url = options.url;
      try {
        const context = await this._contextPromise;
        return (await context.evaluateHandle(addStyleUrl, url)).asElement();
      } catch (error) {
        throw new Error(`Loading style from ${url} failed`);
      }
    }

    if (typeof options.path === 'string') {
      let contents = await readFileAsync(options.path, 'utf8');
      contents += '/*# sourceURL=' + options.path.replace(/\n/g, '') + '*/';
      const context = await this._contextPromise;
      return (await context.evaluateHandle(addStyleContent, contents)).asElement();
    }

    if (typeof options.content === 'string') {
      const context = await this._contextPromise;
      return (await context.evaluateHandle(addStyleContent, options.content)).asElement();
    }

    throw new Error('Provide an object with a `url`, `path` or `content` property');

    /**
     * @param {string} url
     * @return {!Promise<!HTMLElement>}
     */
    async function addStyleUrl(url) {
      const link = document.createElement('link');
      link.rel = 'stylesheet';
      link.href = url;
      const promise = new Promise((res, rej) => {
        link.onload = res;
        link.onerror = rej;
      });
      document.head.appendChild(link);
      await promise;
      return link;
    }

    /**
     * @param {string} content
     * @return {!Promise<!HTMLElement>}
     */
    async function addStyleContent(content) {
      const style = document.createElement('style');
      style.type = 'text/css';
      style.appendChild(document.createTextNode(content));
      const promise = new Promise((res, rej) => {
        style.onload = res;
        style.onerror = rej;
      });
      document.head.appendChild(style);
      await promise;
      return style;
    }
  }

  /**
   * @param {string} selector
   * @param {!Object=} options
   */
  async click(selector, options = {}) {
    const handle = await this.$(selector);
    assert(handle, 'No node found for selector: ' + selector);
    await handle.click(options);
    await handle.dispose();
  }

  /**
   * @param {string} selector
   */
  async focus(selector) {
    const handle = await this.$(selector);
    assert(handle, 'No node found for selector: ' + selector);
    await handle.focus();
    await handle.dispose();
  }

  /**
   * @param {string} selector
   */
  async hover(selector) {
    const handle = await this.$(selector);
    assert(handle, 'No node found for selector: ' + selector);
    await handle.hover();
    await handle.dispose();
  }

  /**
  * @param {string} selector
  * @param {!Array<string>} values
  * @return {!Promise<!Array<string>>}
  */
  select(selector, ...values){
    for (const value of values)
      assert(helper.isString(value), 'Values must be strings. Found value "' + value + '" of type "' + (typeof value) + '"');
    return this.$eval(selector, (element, values) => {
      if (element.nodeName.toLowerCase() !== 'select')
        throw new Error('Element is not a <select> element.');

      const options = Array.from(element.options);
      element.value = undefined;
      for (const option of options) {
        option.selected = values.includes(option.value);
        if (option.selected && !element.multiple)
          break;
      }
      element.dispatchEvent(new Event('input', { 'bubbles': true }));
      element.dispatchEvent(new Event('change', { 'bubbles': true }));
      return options.filter(option => option.selected).map(option => option.value);
    }, values);
  }

  /**
   * @param {string} selector
   */
  async tap(selector) {
    const handle = await this.$(selector);
    assert(handle, 'No node found for selector: ' + selector);
    await handle.tap();
    await handle.dispose();
  }

  /**
   * @param {string} selector
   * @param {string} text
   * @param {{delay: (number|undefined)}=} options
   */
  async type(selector, text, options) {
    const handle = await this.$(selector);
    assert(handle, 'No node found for selector: ' + selector);
    await handle.type(text, options);
    await handle.dispose();
  }

  /**
   * @param {(string|number|Function)} selectorOrFunctionOrTimeout
   * @param {!Object=} options
   * @param {!Array<*>} args
   * @return {!Promise}
   */
  waitFor(selectorOrFunctionOrTimeout, options = {}, ...args) {
    const xPathPattern = '//';

    if (helper.isString(selectorOrFunctionOrTimeout)) {
      const string = /** @type {string} */ (selectorOrFunctionOrTimeout);
      if (string.startsWith(xPathPattern))
        return this.waitForXPath(string, options);
      return this.waitForSelector(string, options);
    }
    if (helper.isNumber(selectorOrFunctionOrTimeout))
      return new Promise(fulfill => setTimeout(fulfill, selectorOrFunctionOrTimeout));
    if (typeof selectorOrFunctionOrTimeout === 'function')
      return this.waitForFunction(selectorOrFunctionOrTimeout, options, ...args);
    return Promise.reject(new Error('Unsupported target type: ' + (typeof selectorOrFunctionOrTimeout)));
  }

  /**
   * @param {string} selector
   * @param {!Object=} options
   * @return {!Promise}
   */
  waitForSelector(selector, options = {}) {
    return this._waitForSelectorOrXPath(selector, false, options);
  }

  /**
   * @param {string} xpath
   * @param {!Object=} options
   * @return {!Promise}
   */
  waitForXPath(xpath, options = {}) {
    return this._waitForSelectorOrXPath(xpath, true, options);
  }

  /**
   * @param {Function|string} pageFunction
   * @param {!Object=} options
   * @return {!Promise}
   */
  waitForFunction(pageFunction, options = {}, ...args) {
    const timeout = helper.isNumber(options.timeout) ? options.timeout : 30000;
    const polling = options.polling || 'raf';
    return new WaitTask(this, pageFunction, 'function', polling, timeout, ...args).promise;
  }

  /**
   * @return {!Promise<string>}
   */
  async title() {
    return this.evaluate(() => document.title);
  }

  /**
   * @param {string} selectorOrXPath
   * @param {boolean} isXPath
   * @param {!Object=} options
   * @return {!Promise}
   */
  _waitForSelectorOrXPath(selectorOrXPath, isXPath, options = {}) {
    const waitForVisible = !!options.visible;
    const waitForHidden = !!options.hidden;
    const polling = waitForVisible || waitForHidden ? 'raf' : 'mutation';
    const timeout = helper.isNumber(options.timeout) ? options.timeout : 30000;
    const title = `${isXPath ? 'XPath' : 'selector'} "${selectorOrXPath}"${waitForHidden ? ' to be hidden' : ''}`;
    return new WaitTask(this, predicate, title, polling, timeout, selectorOrXPath, isXPath, waitForVisible, waitForHidden).promise;

    /**
     * @param {string} selectorOrXPath
     * @param {boolean} isXPath
     * @param {boolean} waitForVisible
     * @param {boolean} waitForHidden
     * @return {?Node|boolean}
     */
    function predicate(selectorOrXPath, isXPath, waitForVisible, waitForHidden) {
      const node = isXPath
        ? document.evaluate(selectorOrXPath, document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue
        : document.querySelector(selectorOrXPath);
      if (!node)
        return waitForHidden;
      if (!waitForVisible && !waitForHidden)
        return node;
      const element = /** @type {Element} */ (node.nodeType === Node.TEXT_NODE ? node.parentElement : node);

      const style = window.getComputedStyle(element);
      const isVisible = style && style.visibility !== 'hidden' && hasVisibleBoundingBox();
      const success = (waitForVisible === isVisible || waitForHidden === !isVisible);
      return success ? node : null;

      /**
       * @return {boolean}
       */
      function hasVisibleBoundingBox() {
        const rect = element.getBoundingClientRect();
        return !!(rect.top || rect.bottom || rect.width || rect.height);
      }
    }
  }

  /**
   * @param {!Protocol.Page.Frame} framePayload
   */
  _navigated(framePayload) {
    this._name = framePayload.name;
    // TODO(lushnikov): remove this once requestInterception has loaderId exposed.
    this._navigationURL = framePayload.url;
    this._url = framePayload.url;
  }

  /**
   * @param {string} url
   */
  _navigatedWithinDocument(url) {
    this._url = url;
  }

  /**
   * @param {string} loaderId
   * @param {string} name
   */
  _onLifecycleEvent(loaderId, name) {
    if (name === 'init') {
      this._loaderId = loaderId;
      this._lifecycleEvents.clear();
    }
    this._lifecycleEvents.add(name);
  }

  _onLoadingStopped() {
    this._lifecycleEvents.add('DOMContentLoaded');
    this._lifecycleEvents.add('load');
  }

  _detach() {
    for (const waitTask of this._waitTasks)
      waitTask.terminate(new Error('waitForFunction failed: frame got detached.'));
    this._detached = true;
    if (this._parentFrame)
      this._parentFrame._childFrames.delete(this);
    this._parentFrame = null;
  }
}
helper.tracePublicAPI(Frame);

class WaitTask {
  /**
   * @param {!Frame} frame
   * @param {Function|string} predicateBody
   * @param {string|number} polling
   * @param {number} timeout
   * @param {!Array<*>} args
   */
  constructor(frame, predicateBody, title, polling, timeout, ...args) {
    if (helper.isString(polling))
      assert(polling === 'raf' || polling === 'mutation', 'Unknown polling option: ' + polling);
    else if (helper.isNumber(polling))
      assert(polling > 0, 'Cannot poll with non-positive interval: ' + polling);
    else
      throw new Error('Unknown polling options: ' + polling);

    this._frame = frame;
    this._polling = polling;
    this._timeout = timeout;
    this._predicateBody = helper.isString(predicateBody) ? 'return ' + predicateBody : 'return (' + predicateBody + ')(...args)';
    this._args = args;
    this._runCount = 0;
    frame._waitTasks.add(this);
    this.promise = new Promise((resolve, reject) => {
      this._resolve = resolve;
      this._reject = reject;
    });
    // Since page navigation requires us to re-install the pageScript, we should track
    // timeout on our end.
    if (timeout) {
      const timeoutError = new TimeoutError(`waiting for ${title} failed: timeout ${timeout}ms exceeded`);
      this._timeoutTimer = setTimeout(() => this.terminate(timeoutError), timeout);
    }
    this.rerun();
  }

  /**
   * @param {!Error} error
   */
  terminate(error) {
    this._terminated = true;
    this._reject(error);
    this._cleanup();
  }

  async rerun() {
    const runCount = ++this._runCount;
    /** @type {?JSHandle} */
    let success = null;
    let error = null;
    try {
      success = await (await this._frame.executionContext()).evaluateHandle(waitForPredicatePageFunction, this._predicateBody, this._polling, this._timeout, ...this._args);
    } catch (e) {
      error = e;
    }

    if (this._terminated || runCount !== this._runCount) {
      if (success)
        await success.dispose();
      return;
    }

    // Ignore timeouts in pageScript - we track timeouts ourselves.
    // If the frame's execution context has already changed, `frame.evaluate` will
    // throw an error - ignore this predicate run altogether.
    if (!error && await this._frame.evaluate(s => !s, success).catch(e => true)) {
      await success.dispose();
      return;
    }

    // When the page is navigated, the promise is rejected.
    // We will try again in the new execution context.
    if (error && error.message.includes('Execution context was destroyed'))
      return;

    // We could have tried to evaluate in a context which was already
    // destroyed.
    if (error && error.message.includes('Cannot find context with specified id'))
      return;

    if (error)
      this._reject(error);
    else
      this._resolve(success);

    this._cleanup();
  }

  _cleanup() {
    clearTimeout(this._timeoutTimer);
    this._frame._waitTasks.delete(this);
    this._runningTask = null;
  }
}

/**
 * @param {string} predicateBody
 * @param {string} polling
 * @param {number} timeout
 * @return {!Promise<*>}
 */
async function waitForPredicatePageFunction(predicateBody, polling, timeout, ...args) {
  const predicate = new Function('...args', predicateBody);
  let timedOut = false;
  if (timeout)
    setTimeout(() => timedOut = true, timeout);
  if (polling === 'raf')
    return await pollRaf();
  if (polling === 'mutation')
    return await pollMutation();
  if (typeof polling === 'number')
    return await pollInterval(polling);

  /**
   * @return {!Promise<*>}
   */
  function pollMutation() {
    const success = predicate.apply(null, args);
    if (success)
      return Promise.resolve(success);

    let fulfill;
    const result = new Promise(x => fulfill = x);
    const observer = new MutationObserver(mutations => {
      if (timedOut) {
        observer.disconnect();
        fulfill();
      }
      const success = predicate.apply(null, args);
      if (success) {
        observer.disconnect();
        fulfill(success);
      }
    });
    observer.observe(document, {
      childList: true,
      subtree: true,
      attributes: true
    });
    return result;
  }

  /**
   * @return {!Promise<*>}
   */
  function pollRaf() {
    let fulfill;
    const result = new Promise(x => fulfill = x);
    onRaf();
    return result;

    function onRaf() {
      if (timedOut) {
        fulfill();
        return;
      }
      const success = predicate.apply(null, args);
      if (success)
        fulfill(success);
      else
        requestAnimationFrame(onRaf);
    }
  }

  /**
   * @param {number} pollInterval
   * @return {!Promise<*>}
   */
  function pollInterval(pollInterval) {
    let fulfill;
    const result = new Promise(x => fulfill = x);
    onTimeout();
    return result;

    function onTimeout() {
      if (timedOut) {
        fulfill();
        return;
      }
      const success = predicate.apply(null, args);
      if (success)
        fulfill(success);
      else
        setTimeout(onTimeout, pollInterval);
    }
  }
}

module.exports = {FrameManager, Frame};