puppeteer/lib/ExecutionContext.js
Andrey Lushnikov 0d0f9b7984 feat(JSHandles): introduce JSHandles (#943)
This patch:
- introduces ExecutionContext class that incapsulates javascript
  execution context. An examples of execution contexts are workers and
  frames
- introduces JSHandle that holds a references to the javascript
  object in ExecutionContext
- inherits ElementHandle from JSHandle

Fixes #382.
2017-10-06 15:35:02 -07:00

193 lines
5.8 KiB
JavaScript

/**
* 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} = require('./helper');
class ExecutionContext {
/**
* @param {!Session} client
* @param {string} contextId
* @param {function(*):!JSHandle} objectHandleFactory
*/
constructor(client, contextId, objectHandleFactory) {
this._client = client;
this._contextId = contextId;
this._objectHandleFactory = objectHandleFactory;
}
/**
* @param {function()|string} pageFunction
* @param {!Array<*>} args
* @return {!Promise<(!Object|undefined)>}
*/
async evaluate(pageFunction, ...args) {
const handle = await this.evaluateHandle(pageFunction, ...args);
const result = await handle.jsonValue();
await handle.dispose();
return result;
}
/**
* @param {function()|string} pageFunction
* @param {!Array<*>} args
* @return {!Promise<!JSHandle>}
*/
async evaluateHandle(pageFunction, ...args) {
if (helper.isString(pageFunction)) {
const contextId = this._contextId;
const expression = pageFunction;
const { exceptionDetails, result: remoteObject } = await this._client.send('Runtime.evaluate', { expression, contextId, returnByValue: false, awaitPromise: true});
if (exceptionDetails)
throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
return this._objectHandleFactory(remoteObject);
}
const { exceptionDetails, result: remoteObject } = await this._client.send('Runtime.callFunctionOn', {
functionDeclaration: pageFunction.toString(),
executionContextId: this._contextId,
arguments: args.map(convertArgument.bind(this)),
returnByValue: false,
awaitPromise: true
});
if (exceptionDetails)
throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
return this._objectHandleFactory(remoteObject);
/**
* @param {*} arg
* @return {*}
* @this {Frame}
*/
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 };
}
}
}
class JSHandle {
/**
* @param {!ExecutionContext} context
* @param {!Session} client
* @param {!Object} remoteObject
*/
constructor(context, client, remoteObject) {
this._context = context;
this._client = client;
this._remoteObject = remoteObject;
this._disposed = false;
}
/**
* @return {!ExecutionContext}
*/
executionContext() {
return this._context;
}
/**
* @param {string} propertyName
* @return {!Promise<?JSHandle>}
*/
async getProperty(propertyName) {
const objectHandle = await this._context.evaluateHandle((object, propertyName) => {
const result = {__proto__: null};
result[propertyName] = object[propertyName];
return result;
}, this, propertyName);
const properties = await objectHandle.getProperties();
const result = properties.get(propertyName) || null;
await objectHandle.dispose();
return result;
}
/**
* @return {!Property<Map<string, !ObjectHandle>>}
*/
async getProperties() {
const response = await this._client.send('Runtime.getProperties', {
objectId: this._remoteObject.objectId,
ownProperties: true
});
const result = new Map();
for (const property of response.result) {
if (!property.enumerable)
continue;
result.set(property.name, this._context._objectHandleFactory(property.value));
}
return result;
}
/**
* @return {!Promise<?Object>}
*/
async jsonValue() {
if (this._remoteObject.objectId) {
const jsonString = await this._context.evaluate(object => JSON.stringify(object), this);
return JSON.parse(jsonString);
}
return helper.valueFromRemoteObject(this._remoteObject);
}
/**
* @return {?ElementHandle}
*/
asElement() {
return null;
}
async dispose() {
if (this._disposed)
return;
this._disposed = true;
await helper.releaseObject(this._client, this._remoteObject);
}
/**
* @override
* @return {string}
*/
toString() {
if (this._remoteObject.objectId) {
const type = this._remoteObject.subtype || this._remoteObject.type;
return 'JSHandle@' + type;
}
return helper.valueFromRemoteObject(this._remoteObject) + '';
}
}
helper.tracePublicAPI(JSHandle);
module.exports = {ExecutionContext, JSHandle};