fix(page.evaluate): jsonValue should ignore toJSON property (#1098)

Currently, JSHandle.jsonValue() is implemented as in-page JSON.stringify
call and consequent JSON.parse in node. This approach proved to be
unfortunate for automation purposes: if page author overrode the
Object.prototype.toJSON method, then it's harder for puppeteer to
interact with the page.

This patch switches JSHandle.jsonValue to use protocol serialization
that ignores toJSON property. THis also changes the `page.evaluate`
behavior since it is based on JSHandle.jsonValue().

Fixes #1003.

BREAKING CHANGE:
`page.evaluate` no longer calls toJSON when generating return value.
For the old behavior, do JSON.parse/JSON.stringify manually:

```js
const json = JSON.parse(await page.evaluate(() => JSON.stringify(obj)));
```

docs/api.md

@@ -1677,7 +1677,9 @@ Fetches a single property from the referenced object.
 #### jsHandle.jsonValue()
 - returns: <[Promise]<[Object]>>
 
-Returns a JSON representation of the object. The JSON is generated by running [`JSON.stringify`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify) on the object in page and consequent [`JSON.parse`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse) in puppeteer.
+Returns a JSON representation of the object. If the object has a
+[`toJSON`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#toJSON()_behavior)
+function, it **will not be called**.
 
 > **NOTE** The method will throw if the referenced object is not stringifiable.
 

lib/ExecutionContext.js

@@ -168,8 +168,13 @@ class JSHandle {
    */
   async jsonValue() {
     if (this._remoteObject.objectId) {
-      const jsonString = await this._context.evaluate(object => JSON.stringify(object), this);
-      return JSON.parse(jsonString);
+      const response = await this._client.send('Runtime.callFunctionOn', {
+        functionDeclaration: 'function() { return this; }',
+        objectId: this._remoteObject.objectId,
+        returnByValue: true,
+        awaitPromise: true,
+      });
+      return helper.valueFromRemoteObject(response.result);
     }
     return helper.valueFromRemoteObject(this._remoteObject);
   }

test/test.js

@@ -429,16 +429,16 @@ describe('Page', function() {
       const json = await aHandle.jsonValue();
       expect(json).toEqual({foo: 'bar'});
     }));
-    it('should work with dates', SX(async function() {
+    it('should not work with dates', SX(async function() {
       const dateHandle = await page.evaluateHandle(() => new Date('2017-09-26T00:00:00.000Z'));
       const json = await dateHandle.jsonValue();
-      expect(json).toBe('2017-09-26T00:00:00.000Z');
+      expect(json).toEqual({});
     }));
     it('should throw for circular objects', SX(async function() {
       const windowHandle = await page.evaluateHandle('window');
       let error = null;
       await windowHandle.jsonValue().catch(e => error = e);
-      expect(error.message).toContain('Converting circular structure to JSON');
+      expect(error.message).toContain('Object reference chain is too long');
     }));
   });