chore: reuse WaitTask between browsers (#67)

src/chromium/DOMWorld.ts

@@ -17,15 +17,15 @@
 
 import * as fs from 'fs';
 import * as types from '../types';
-import { TimeoutError } from '../Errors';
 import { ExecutionContext } from './ExecutionContext';
 import { Frame } from './Frame';
 import { FrameManager } from './FrameManager';
-import { assert, helper } from '../helper';
+import { helper } from '../helper';
 import { ElementHandle, JSHandle } from './JSHandle';
 import { LifecycleWatcher } from './LifecycleWatcher';
 import { TimeoutSettings } from '../TimeoutSettings';
-import { ClickOptions, MultiClickOptions, PointerActionOptions, SelectOption } from '../input';
+import { WaitTask, WaitTaskParams } from '../waitTask';
+
 const readFileAsync = helper.promisify(fs.readFile);
 
 export class DOMWorld {
@@ -36,7 +36,7 @@ export class DOMWorld {
   private _contextPromise: Promise<ExecutionContext>;
   private _contextResolveCallback: ((c: ExecutionContext) => void) | null;
   private _context: ExecutionContext | null;
-  _waitTasks = new Set<WaitTask>();
+  _waitTasks = new Set<WaitTask<JSHandle>>();
   private _detached = false;
 
   constructor(frameManager: FrameManager, frame: Frame, timeoutSettings: TimeoutSettings) {
@@ -366,177 +366,3 @@ export class DOMWorld {
   }
 }
 
-type WaitTaskParams = {
-  predicateBody: Function | string;
-  title: string;
-  polling: string | number;
-  timeout: number;
-  args: any[];
-};
-
-class WaitTask {
-  readonly promise: Promise<JSHandle>;
-  private _cleanup: () => void;
-  private _params: WaitTaskParams & { predicateBody: string };
-  private _runCount: number;
-  private _resolve: (result: JSHandle) => void;
-  private _reject: (reason: Error) => void;
-  private _timeoutTimer: NodeJS.Timer;
-  private _terminated: boolean;
-
-  constructor(params: WaitTaskParams, cleanup: () => void) {
-    if (helper.isString(params.polling))
-      assert(params.polling === 'raf' || params.polling === 'mutation', 'Unknown polling option: ' + params.polling);
-    else if (helper.isNumber(params.polling))
-      assert(params.polling > 0, 'Cannot poll with non-positive interval: ' + params.polling);
-    else
-      throw new Error('Unknown polling options: ' + params.polling);
-
-    this._params = {
-      ...params,
-      predicateBody: helper.isString(params.predicateBody) ? 'return (' + params.predicateBody + ')' : 'return (' + params.predicateBody + ')(...args)'
-    };
-    this._cleanup = cleanup;
-    this._runCount = 0;
-    this.promise = new Promise<JSHandle>((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 (params.timeout) {
-      const timeoutError = new TimeoutError(`waiting for ${params.title} failed: timeout ${params.timeout}ms exceeded`);
-      this._timeoutTimer = setTimeout(() => this.terminate(timeoutError), params.timeout);
-    }
-  }
-
-  terminate(error: Error) {
-    this._terminated = true;
-    this._reject(error);
-    this._doCleanup();
-  }
-
-  async rerun(context: ExecutionContext) {
-    const runCount = ++this._runCount;
-    let success: JSHandle | null = null;
-    let error = null;
-    try {
-      success = await context.evaluateHandle(waitForPredicatePageFunction, this._params.predicateBody, this._params.polling, this._params.timeout, ...this._params.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 execution context has been already destroyed, `context.evaluate` will
-    // throw an error - ignore this predicate run altogether.
-    if (!error && await context.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._doCleanup();
-  }
-
-  _doCleanup() {
-    clearTimeout(this._timeoutTimer);
-    this._cleanup();
-  }
-}
-
-async function waitForPredicatePageFunction(predicateBody: string, polling: string | number, timeout: number, ...args): Promise<any> {
-  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);
-
-  function pollMutation(): Promise<any> {
-    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;
-  }
-
-  function pollRaf(): Promise<any> {
-    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);
-    }
-  }
-
-  function pollInterval(pollInterval: number): Promise<any> {
-    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);
-    }
-  }
-}

src/firefox/DOMWorld.ts

@@ -15,13 +15,12 @@
  * limitations under the License.
  */
 
-import {helper, assert} from '../helper';
-import {TimeoutError} from '../Errors';
 import * as fs from 'fs';
 import * as util from 'util';
 import * as types from '../types';
 import {ElementHandle, JSHandle} from './JSHandle';
 import { ExecutionContext } from './ExecutionContext';
+import { WaitTaskParams, WaitTask } from '../waitTask';
 
 const readFileAsync = util.promisify(fs.readFile);
 
@@ -31,7 +30,8 @@ export class DOMWorld {
   _documentPromise: any;
   _contextPromise: any;
   _contextResolveCallback: any;
-  _waitTasks: Set<WaitTask>;
+  private _context: ExecutionContext | null;
+  _waitTasks: Set<WaitTask<JSHandle>>;
   _detached: boolean;
   constructor(frame, timeoutSettings) {
     this._frame = frame;
@@ -50,12 +50,13 @@ export class DOMWorld {
     return this._frame;
   }
 
-  _setContext(context) {
+  _setContext(context: ExecutionContext) {
+    this._context = context;
     if (context) {
       this._contextResolveCallback.call(null, context);
       this._contextResolveCallback = null;
       for (const waitTask of this._waitTasks)
-        waitTask.rerun();
+        waitTask.rerun(context);
     } else {
       this._documentPromise = null;
       this._contextPromise = new Promise(fulfill => {
@@ -250,7 +251,14 @@ export class DOMWorld {
       polling = 'raf',
       timeout = this._timeoutSettings.timeout(),
     } = options;
-    return new WaitTask(this, pageFunction, 'function', polling, timeout, ...args).promise;
+    const params: WaitTaskParams = {
+      predicateBody: pageFunction,
+      title: 'function',
+      polling,
+      timeout,
+      args
+    };
+    return this._scheduleWaitTask(params);
   }
 
   async title(): Promise<string> {
@@ -265,8 +273,14 @@ export class DOMWorld {
     } = options;
     const polling = waitForVisible || waitForHidden ? 'raf' : 'mutation';
     const title = `${isXPath ? 'XPath' : 'selector'} "${selectorOrXPath}"${waitForHidden ? ' to be hidden' : ''}`;
-    const waitTask = new WaitTask(this, predicate, title, polling, timeout, selectorOrXPath, isXPath, waitForVisible, waitForHidden);
+    const params: WaitTaskParams = {
-    const handle = await waitTask.promise;
+      predicateBody: predicate,
+      title,
+      polling,
+      timeout,
+      args: [selectorOrXPath, isXPath, waitForVisible, waitForHidden]
+    };
+    const handle = await this._scheduleWaitTask(params);
     if (!handle.asElement()) {
       await handle.dispose();
       return null;
@@ -294,174 +308,12 @@ export class DOMWorld {
       }
     }
   }
-}
 
-class WaitTask {
+  private _scheduleWaitTask(params: WaitTaskParams): Promise<JSHandle> {
-  promise: any;
+    const task = new WaitTask(params, () => this._waitTasks.delete(task));
-  _domWorld: any;
+    this._waitTasks.add(task);
-  _polling: any;
+    if (this._context)
-  _timeout: any;
+      task.rerun(this._context);
-  _predicateBody: string;
+    return task.promise;
-  _args: any[];
-  _runCount: number;
-  _resolve: (value?: unknown) => void;
-  _reject: (reason?: any) => void;
-  _timeoutTimer: NodeJS.Timer;
-  _terminated: boolean;
-  _runningTask: any;
-  constructor(domWorld: DOMWorld, predicateBody: Function | string, title, polling: string | number, timeout: number, ...args: Array<any>) {
-    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._domWorld = domWorld;
-    this._polling = polling;
-    this._timeout = timeout;
-    this._predicateBody = helper.isString(predicateBody) ? 'return (' + predicateBody + ')' : 'return (' + predicateBody + ')(...args)';
-    this._args = args;
-    this._runCount = 0;
-    domWorld._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();
-  }
-
-  terminate(error: Error) {
-    this._terminated = true;
-    this._reject(error);
-    this._cleanup();
-  }
-
-  async rerun() {
-    const runCount = ++this._runCount;
-    let success: JSHandle | null = null;
-    let error = null;
-    try {
-      success = await this._domWorld.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._domWorld.evaluate(s => !s, success).catch(e => true)) {
-      await success.dispose();
-      return;
-    }
-
-    // When the page is navigated, the promise is rejected.
-    // Try again right away.
-    if (error && error.message.includes('Execution context was destroyed')) {
-      this.rerun();
-      return;
-    }
-
-    if (error)
-      this._reject(error);
-    else
-      this._resolve(success);
-
-    this._cleanup();
-  }
-
-  _cleanup() {
-    clearTimeout(this._timeoutTimer);
-    this._domWorld._waitTasks.delete(this);
-    this._runningTask = null;
-  }
-}
-
-async function waitForPredicatePageFunction(predicateBody: string, polling: string, timeout: number, ...args): Promise<any> {
-  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);
-
-  function pollMutation(): Promise<any> {
-    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;
-  }
-
-  function pollRaf(): Promise<any> {
-    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);
-    }
-  }
-
-  function pollInterval(pollInterval: number): Promise<any> {
-    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);
-    }
   }
 }

src/waitTask.ts

@@ -0,0 +1,182 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+import { assert, helper } from './helper';
+import * as types from './types';
+import { TimeoutError } from './Errors';
+
+export type WaitTaskParams = {
+  // TODO: ensure types.
+  predicateBody: Function | string;
+  title: string;
+  polling: string | number;
+  timeout: number;
+  args: any[];
+};
+
+export class WaitTask<Handle extends types.Handle> {
+  readonly promise: Promise<Handle>;
+  private _cleanup: () => void;
+  private _params: WaitTaskParams & { predicateBody: string };
+  private _runCount: number;
+  private _resolve: (result: Handle) => void;
+  private _reject: (reason: Error) => void;
+  private _timeoutTimer: NodeJS.Timer;
+  private _terminated: boolean;
+
+  constructor(params: WaitTaskParams, cleanup: () => void) {
+    if (helper.isString(params.polling))
+      assert(params.polling === 'raf' || params.polling === 'mutation', 'Unknown polling option: ' + params.polling);
+    else if (helper.isNumber(params.polling))
+      assert(params.polling > 0, 'Cannot poll with non-positive interval: ' + params.polling);
+    else
+      throw new Error('Unknown polling options: ' + params.polling);
+
+    this._params = {
+      ...params,
+      predicateBody: helper.isString(params.predicateBody) ? 'return (' + params.predicateBody + ')' : 'return (' + params.predicateBody + ')(...args)'
+    };
+    this._cleanup = cleanup;
+    this._runCount = 0;
+    this.promise = new Promise<Handle>((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 (params.timeout) {
+      const timeoutError = new TimeoutError(`waiting for ${params.title} failed: timeout ${params.timeout}ms exceeded`);
+      this._timeoutTimer = setTimeout(() => this.terminate(timeoutError), params.timeout);
+    }
+  }
+
+  terminate(error: Error) {
+    this._terminated = true;
+    this._reject(error);
+    this._doCleanup();
+  }
+
+  async rerun(context: types.EvaluationContext<Handle>) {
+    const runCount = ++this._runCount;
+    let success: Handle | null = null;
+    let error = null;
+    try {
+      success = await context.evaluateHandle(waitForPredicatePageFunction, this._params.predicateBody, this._params.polling, this._params.timeout, ...this._params.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 execution context has been already destroyed, `context.evaluate` will
+    // throw an error - ignore this predicate run altogether.
+    if (!error && await context.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._doCleanup();
+  }
+
+  _doCleanup() {
+    clearTimeout(this._timeoutTimer);
+    this._cleanup();
+  }
+}
+
+async function waitForPredicatePageFunction(predicateBody: string, polling: string | number, timeout: number, ...args): Promise<any> {
+  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);
+
+  function pollMutation(): Promise<any> {
+    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;
+  }
+
+  function pollRaf(): Promise<any> {
+    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);
+    }
+  }
+
+  function pollInterval(pollInterval: number): Promise<any> {
+    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);
+    }
+  }
+}

src/webkit/FrameManager.ts

@@ -27,6 +27,8 @@ import { NetworkManager, NetworkManagerEvents, Request, Response } from './Netwo
 import { Page } from './Page';
 import { Protocol } from './protocol';
 import { MultiClickOptions, ClickOptions, SelectOption } from '../input';
+import { WaitTask, WaitTaskParams } from '../waitTask';
+
 const readFileAsync = helper.promisify(fs.readFile);
 
 export const FrameManagerEvents = {
@@ -238,8 +240,8 @@ export class Frame {
   _detached: boolean;
   _loaderId: string;
   _lifecycleEvents: Set<string>;
-  _waitTasks: Set<WaitTask>;
+  _waitTasks: Set<WaitTask<JSHandle>>;
-  _executionContext: ExecutionContext;
+  _executionContext: ExecutionContext | null;
   _contextPromise: Promise<ExecutionContext>;
   _contextResolveCallback: (arg: ExecutionContext) => void;
   _childFrames: Set<Frame>;
@@ -300,7 +302,14 @@ export class Frame {
       polling = 'raf',
       timeout = this._frameManager._timeoutSettings.timeout(),
     } = options;
-    return new WaitTask(this, pageFunction, 'function', polling, timeout, ...args).promise;
+    const params: WaitTaskParams = {
+      predicateBody: pageFunction,
+      title: 'function',
+      polling,
+      timeout,
+      args
+    };
+    return this._scheduleWaitTask(params);
   }
 
   async executionContext(): Promise<ExecutionContext> {
@@ -606,8 +615,14 @@ export class Frame {
     } = options;
     const polling = waitForVisible || waitForHidden ? 'raf' : 'mutation';
     const title = `${isXPath ? 'XPath' : 'selector'} "${selectorOrXPath}"${waitForHidden ? ' to be hidden' : ''}`;
-    const waitTask = new WaitTask(this, predicate, title, polling, timeout, selectorOrXPath, isXPath, waitForVisible, waitForHidden);
+    const params: WaitTaskParams = {
-    const handle = await waitTask.promise;
+      predicateBody: predicate,
+      title,
+      polling,
+      timeout,
+      args: [selectorOrXPath, isXPath, waitForVisible, waitForHidden]
+    };
+    const handle = await this._scheduleWaitTask(params);
     if (!handle.asElement()) {
       await handle.dispose();
       return null;
@@ -676,7 +691,7 @@ export class Frame {
       this._contextResolveCallback.call(null, context);
       this._contextResolveCallback = null;
       for (const waitTask of this._waitTasks)
-        waitTask.rerun();
+        waitTask.rerun(context);
     } else {
       this._documentPromise = null;
       this._contextPromise = new Promise(fulfill => {
@@ -684,6 +699,14 @@ export class Frame {
       });
     }
   }
+
+  private _scheduleWaitTask(params: WaitTaskParams): Promise<JSHandle> {
+    const task = new WaitTask(params, () => this._waitTasks.delete(task));
+    this._waitTasks.add(task);
+    if (this._executionContext)
+      task.rerun(this._executionContext);
+    return task.promise;
+  }
 }
 
 /**
@@ -773,181 +796,3 @@ class NextNavigationWatchdog {
     clearTimeout(this._timeoutId);
   }
 }
-
-class WaitTask {
-  promise: Promise<any>;
-  _domWorld: any;
-  _polling: string | number;
-  _timeout: number;
-  _predicateBody: string;
-  _args: any[];
-  _runCount: number;
-  _resolve: (value?: unknown) => void;
-  _reject: (reason?: any) => void;
-  _timeoutTimer: NodeJS.Timer;
-  _terminated: boolean;
-  _runningTask: any;
-  constructor(domWorld: Frame, predicateBody: Function | string, title, polling: string | number, timeout: number, ...args: Array<any>) {
-    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._domWorld = domWorld;
-    this._polling = polling;
-    this._timeout = timeout;
-    this._predicateBody = helper.isString(predicateBody) ? 'return (' + predicateBody + ')' : 'return (' + predicateBody + ')(...args)';
-    this._args = args;
-    this._runCount = 0;
-    domWorld._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();
-  }
-
-  terminate(error: Error) {
-    this._terminated = true;
-    this._reject(error);
-    this._cleanup();
-  }
-
-  async rerun() {
-    const runCount = ++this._runCount;
-    /** @type {?JSHandle} */
-    let success: JSHandle | null = null;
-    let error = null;
-    try {
-      success = await (await this._domWorld.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._domWorld.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;
-    // In WebKit cross-process navigation leads to targetDestroyed (followed
-    // by targetCreated).
-    if (error && error.message.includes('Target closed'))
-      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._domWorld._waitTasks.delete(this);
-    this._runningTask = null;
-  }
-}
-
-async function waitForPredicatePageFunction(predicateBody: string, polling: string, timeout: number, ...args): Promise<any> {
-  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);
-
-  function pollMutation(): Promise<any> {
-    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;
-  }
-
-  function pollRaf(): Promise<any> {
-    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);
-    }
-  }
-
-  function pollInterval(pollInterval: number): Promise<any> {
-    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);
-    }
-  }
-}