Implement Frame.evaluate

This patch implements Frame.evaluate method.

References #4.

lib/FrameManager.js

@@ -15,6 +15,7 @@
  */
 
 let EventEmitter = require('events');
+let helper = require('./helper');
 
 class FrameManager extends EventEmitter {
   /**
@@ -37,9 +38,14 @@ class FrameManager extends EventEmitter {
     this._frames = new Map();
     this._mainFrame = this._addFramesRecursively(null, frameTree);
 
-    this._client.on('Page.frameAttached', event => this._frameAttached(event.frameId, event.parentFrameId));
-    this._client.on('Page.frameNavigated', event => this._frameNavigated(event.frame));
-    this._client.on('Page.frameDetached', event => this._frameDetached(event.frameId));
+    /** @type {!Map<string, string>} */
+    this._frameIdToExecutionContextId = 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.frameDetached', event => this._onFrameDetached(event.frameId));
+    this._client.on('Runtime.executionContextCreated', event => this._onExecutionContextCreated(event.context));
+    this._client.on('Runtime.executionContextDestroyed', event => this._onExecutionContextDestroyed(event.executionContextId));
   }
 
   /**
@@ -61,7 +67,7 @@ class FrameManager extends EventEmitter {
    * @param {?string} parentFrameId
    * @return {?Frame}
    */
-  _frameAttached(frameId, parentFrameId) {
+  _onFrameAttached(frameId, parentFrameId) {
     if (this._frames.has(frameId))
       return;
 
@@ -71,7 +77,7 @@ class FrameManager extends EventEmitter {
       return;
     }
     let parentFrame = this._frames.get(parentFrameId);
-    let frame = new Frame(parentFrame, frameId, null);
+    let frame = new Frame(this, parentFrame, frameId, null);
     this._frames.set(frame._id, frame);
     this.emit(FrameManager.Events.FrameAttached, frame);
   }
@@ -79,7 +85,7 @@ class FrameManager extends EventEmitter {
   /**
    * @param {!Object} framePayload
    */
-  _frameNavigated(framePayload) {
+  _onFrameNavigated(framePayload) {
     let frame = this._frames.get(framePayload.id);
     if (!frame) {
       // Simulate missed "frameAttached" for a main frame navigation to the new backend process.
@@ -92,12 +98,21 @@ class FrameManager extends EventEmitter {
   /**
    * @param {string} frameId
    */
-  _frameDetached(frameId) {
+  _onFrameDetached(frameId) {
     let frame = this._frames.get(frameId);
     if (frame)
       this._removeFramesRecursively(frame);
   }
 
+  _onExecutionContextCreated(context) {
+    if (context.auxData && context.auxData.isDefault && context.auxData.frameId)
+      this._frameIdToExecutionContextId.set(context.auxData.frameId, context.id);
+  }
+
+  _onExecutionContextDestroyed(executionContextId) {
+    this._frameIdToExecutionContextId.delete(executionContextId);
+  }
+
   /**
    * @param {!Frame} frame
    * @param {string} newFrameId
@@ -121,7 +136,7 @@ class FrameManager extends EventEmitter {
    */
   _addFramesRecursively(parentFrame, frameTreePayload) {
     let framePayload = frameTreePayload.frame;
-    let frame = new Frame(parentFrame, framePayload.id, framePayload);
+    let frame = new Frame(this, parentFrame, framePayload.id, framePayload);
     this._frames.set(frame._id, frame);
 
     for (let i = 0; frameTreePayload.childFrames && i < frameTreePayload.childFrames.length; ++i)
@@ -139,6 +154,28 @@ class FrameManager extends EventEmitter {
     this._frames.delete(frame._id);
     this.emit(FrameManager.Events.FrameDetached, frame);
   }
+
+  /**
+   * @param {!Frame} frame
+   * @param {function()} fun
+   * @param {!Array<*>} args
+   * @return {!Promise<(!Object|undefined)>}
+   */
+  async _evaluateOnFrame(frame, fun, ...args) {
+    let contextId = undefined;
+    if (!frame.isMainFrame()) {
+      contextId = this._frameIdToExecutionContextId.get(frame._id);
+      console.assert(contextId, 'Frame does not have default context to evaluate in!');
+    }
+    let syncExpression = helper.evaluationString(fun, ...args);
+    let expression = `Promise.resolve(${syncExpression})`;
+    let { exceptionDetails, result: remoteObject }  = await this._client.send('Runtime.evaluate', { expression, contextId, returnByValue: true, awaitPromise: true });
+    if (exceptionDetails) {
+      let message = await helper.getExceptionMessage(this._client, exceptionDetails);
+      throw new Error('Evaluation failed: ' + message);
+    }
+    return remoteObject.value;
+  }
 }
 
 /** @enum {string} */
@@ -153,11 +190,13 @@ FrameManager.Events = {
  */
 class Frame {
   /**
+   * @param {!FrameManager} frameManager
    * @param {?Frame} parentFrame
    * @param {string} frameId
    * @param {?Object} payload
    */
-  constructor(parentFrame, frameId, payload) {
+  constructor(frameManager, parentFrame, frameId, payload) {
+    this._frameManager = frameManager;
     this._parentFrame = parentFrame;
     this._url = '';
     this._id = frameId;
@@ -169,6 +208,15 @@ class Frame {
       this._parentFrame._childFrames.add(this);
   }
 
+  /**
+   * @param {function()} fun
+   * @param {!Array<*>} args
+   * @return {!Promise<(!Object|undefined)>}
+   */
+  async evaluate(fun, ...args) {
+    return this._frameManager._evaluateOnFrame(this, fun, ...args);
+  }
+
   /**
    * @return {string}
    */