puppeteer/lib/ExecutionContext.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 {helper, assert} = require('./helper');
const {createJSHandle, JSHandle} = require('./JSHandle');

const EVALUATION_SCRIPT_URL = '__puppeteer_evaluation_script__';
const SOURCE_URL_REGEX = /^[\040\t]*\/\/[@#] sourceURL=\s*(\S*?)\s*$/m;

class ExecutionContext {
  /**
   * @param {!Puppeteer.CDPSession} client
   * @param {!Protocol.Runtime.ExecutionContextDescription} contextPayload
   * @param {?Puppeteer.DOMWorld} world
   */
  constructor(client, contextPayload, world) {
    this._client = client;
    this._world = world;
    this._contextId = contextPayload.id;
  }

  /**
   * @return {?Puppeteer.Frame}
   */
  frame() {
    return this._world ? this._world.frame() : null;
  }

  /**
   * @param {Function|string} pageFunction
   * @param {...*} args
   * @return {!Promise<(!Object|undefined)>}
   */
  async evaluate(pageFunction, ...args) {
    const handle = await this.evaluateHandle(pageFunction, ...args);
    const result = await handle.jsonValue().catch(error => {
      if (error.message.includes('Object reference chain is too long'))
        return;
      if (error.message.includes('Object couldn\'t be returned by value'))
        return;
      throw error;
    });
    await handle.dispose();
    return result;
  }

  /**
   * @param {Function|string} pageFunction
   * @param {...*} args
   * @return {!Promise<!JSHandle>}
   */
  async evaluateHandle(pageFunction, ...args) {
    const suffix = `//# sourceURL=${EVALUATION_SCRIPT_URL}`;

    if (helper.isString(pageFunction)) {
      const contextId = this._contextId;
      const expression = /** @type {string} */ (pageFunction);
      const expressionWithSourceUrl = SOURCE_URL_REGEX.test(expression) ? expression : expression + '\n' + suffix;
      const {exceptionDetails, result: remoteObject} = await this._client.send('Runtime.evaluate', {
        expression: expressionWithSourceUrl,
        contextId,
        returnByValue: false,
        awaitPromise: true,
        userGesture: true
      }).catch(rewriteError);
      if (exceptionDetails)
        throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
      return createJSHandle(this, remoteObject);
    }

    if (typeof pageFunction !== 'function')
      throw new Error('The following is not a function: ' + pageFunction);

    let functionText = pageFunction.toString();
    try {
      new Function('(' + functionText + ')');
    } catch (e1) {
      // This means we might have a function shorthand. Try another
      // time prefixing 'function '.
      if (functionText.startsWith('async '))
        functionText = 'async function ' + functionText.substring('async '.length);
      else
        functionText = 'function ' + functionText;
      try {
        new Function('(' + functionText  + ')');
      } catch (e2) {
        // We tried hard to serialize, but there's a weird beast here.
        throw new Error('Passed function is not well-serializable!');
      }
    }
    let callFunctionOnPromise;
    try {
      callFunctionOnPromise = this._client.send('Runtime.callFunctionOn', {
        functionDeclaration: functionText + '\n' + suffix + '\n',
        executionContextId: this._contextId,
        arguments: args.map(convertArgument.bind(this)),
        returnByValue: false,
        awaitPromise: true,
        userGesture: true
      });
    } catch (err) {
      if (err instanceof TypeError && err.message === 'Converting circular structure to JSON')
        err.message += ' Are you passing a nested JSHandle?';
      throw err;
    }
    const { exceptionDetails, result: remoteObject } = await callFunctionOnPromise.catch(rewriteError);
    if (exceptionDetails)
      throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
    return createJSHandle(this, remoteObject);

    /**
     * @param {*} arg
     * @return {*}
     * @this {ExecutionContext}
     */
    function convertArgument(arg) {
      if (Object.is(arg, -0))
        return { unserializableValue: '-0' };
      if (Object.is(arg, Infinity))
        return { unserializableValue: 'Infinity' };
      if (Object.is(arg, -Infinity))
        return { unserializableValue: '-Infinity' };
      if (Object.is(arg, NaN))
        return { unserializableValue: 'NaN' };
      const objectHandle = arg && (arg instanceof JSHandle) ? arg : null;
      if (objectHandle) {
        if (objectHandle._context !== this)
          throw new Error('JSHandles can be evaluated only in the context they were created!');
        if (objectHandle._disposed)
          throw new Error('JSHandle is disposed!');
        if (objectHandle._remoteObject.unserializableValue)
          return { unserializableValue: objectHandle._remoteObject.unserializableValue };
        if (!objectHandle._remoteObject.objectId)
          return { value: objectHandle._remoteObject.value };
        return { objectId: objectHandle._remoteObject.objectId };
      }
      return { value: arg };
    }

    /**
     * @param {!Error} error
     * @return {!Protocol.Runtime.evaluateReturnValue}
     */
    function rewriteError(error) {
      if (error.message.endsWith('Cannot find context with specified id'))
        throw new Error('Execution context was destroyed, most likely because of a navigation.');
      throw error;
    }
  }

  /**
   * @param {!JSHandle} prototypeHandle
   * @return {!Promise<!JSHandle>}
   */
  async queryObjects(prototypeHandle) {
    assert(!prototypeHandle._disposed, 'Prototype JSHandle is disposed!');
    assert(prototypeHandle._remoteObject.objectId, 'Prototype JSHandle must not be referencing primitive value');
    const response = await this._client.send('Runtime.queryObjects', {
      prototypeObjectId: prototypeHandle._remoteObject.objectId
    });
    return createJSHandle(this, response.objects);
  }
}

module.exports = {ExecutionContext, EVALUATION_SCRIPT_URL};