Make helper.getExceptionMessage synchronous

We now have description of an exception, no need for a roundtrip
to the backend.

lib/FrameManager.js

@@ -165,10 +165,8 @@ class FrameManager extends EventEmitter {
     }
     expression = `Promise.resolve(${expression})`;
     let { exceptionDetails, result: remoteObject }  = await this._client.send('Runtime.evaluate', { expression, contextId, returnByValue: false, awaitPromise: true });
-    if (exceptionDetails) {
-      let message = await helper.getExceptionMessage(this._client, exceptionDetails);
-      throw new Error('Evaluation failed: ' + message);
-    }
+    if (exceptionDetails)
+      throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
     return await helper.serializeRemoteObject(this._client, remoteObject);
   }
 
@@ -190,10 +188,8 @@ class FrameManager extends EventEmitter {
       awaitPromise: true,
       returnByValue: false,
     });
-    if (exceptionDetails) {
-      let message = await helper.getExceptionMessage(this._client, exceptionDetails);
-      throw new Error('Evaluation failed: ' + message);
-    }
+    if (exceptionDetails)
+      throw new Error('Evaluation failed: ' + helper.getExceptionMessage(exceptionDetails));
 
     /**
      * @param {string} selector

lib/Page.js

@@ -207,8 +207,8 @@ class Page extends EventEmitter {
   /**
    * @param {!Object} exceptionDetails
    */
-  async _handleException(exceptionDetails) {
-    let message = await helper.getExceptionMessage(this._client, exceptionDetails);
+  _handleException(exceptionDetails) {
+    let message = helper.getExceptionMessage(exceptionDetails);
     this.emit(Page.Events.PageError, new Error(message));
   }
 

lib/helper.js

@@ -25,24 +25,13 @@ class Helper {
   }
 
   /**
-   * @param {!Connection} client
    * @param {!Object} exceptionDetails
    * @return {string}
    */
-  static async getExceptionMessage(client, exceptionDetails) {
-    let message = '';
-    let exception = exceptionDetails.exception;
-    if (exception) {
-      let response = await client.send('Runtime.callFunctionOn', {
-        objectId: exception.objectId,
-        functionDeclaration: 'function() { return this.message; }',
-        returnByValue: true,
-      });
-      message = response.result.value;
-    } else {
-      message = exceptionDetails.text;
-    }
-
+  static getExceptionMessage(exceptionDetails) {
+    if (exceptionDetails.exception)
+      return exceptionDetails.exception.description;
+    let message = exceptionDetails.text;
     if (exceptionDetails.stackTrace) {
       for (let callframe of exceptionDetails.stackTrace.callFrames) {
         let location = callframe.url + ':' + callframe.lineNumber + ':' + callframe.columnNumber;

test/test.js

@@ -240,7 +240,7 @@ describe('Puppeteer', function() {
         await page.waitFor('*');
         fail('Failed waitFor did not throw.');
       } catch (e) {
-        expect(e.message).toContain('Evaluation failed: document.querySelector is not a function');
+        expect(e.message).toContain('document.querySelector is not a function');
       }
     }));
     it('should throw when frame is detached', SX(async function() {