Pass error messages from native messaging to web-app.

remoting/webapp/crd/js/host_daemon_facade.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview
  * Class to communicate with the host daemon via Native Messaging.
  */
 
 'use strict';
@@ skipping 178 matching lines @@
   var reply = this.pendingReplies_[id];
   if (!reply) {
     console.error('NativeMessaging: unexpected id: ', id);
     return;
   }
   delete this.pendingReplies_[id];
 
   try {
     var type = base.getStringAttr(message, 'type');
     if (type != reply.type) {
-      throw 'Expected reply type: ' + reply.type + ', got: ' + type;
+      throw new Error('Expected reply type: ' + reply.type + ', got: ' + type);
+    }
+    var error_message = base.getStringAttr(message, 'error_message', '');
+    if (error_message) {
+      var error_location = base.getStringAttr(message, 'error_location',
+                                              '<unknown>')
+      console.error(error_message + ' at ' + error_location);
     }
     reply.deferred.resolve(message);

[Sergey Ulanov, 2015/08/06 22:40:57]

should we call reject() in case there was an error?

[Jamie, 2015/08/06 23:06:17]

I don't think so. The contract here is that the caller requests that a message
be sent and the Promise is fulfilled when the reply arrives, whether it be
success or failure. This code should ideally be generic and not attempt any
parsing of the message at all (TBH, I'm not convinced that this is the right
place to print the error, but the alternative is duplicating it at each
call-site, which seems worse).

   } catch (/** @type {*} */ e) {
     console.error('Error while processing native message', e);
     reply.deferred.reject(remoting.Error.unexpected());
   }
 };
 
 /**
  * @return {void} Nothing.
  * @private
  */
@@ skipping 266 matching lines @@
     authorizationCode: authorizationCode
   }).then(function(reply) {
     var refreshToken = base.getStringAttr(reply, 'refreshToken');
     if (refreshToken) {
       return refreshToken
     } else {
       throw remoting.Error.unexpected('Missing refreshToken');
     }
   });
 };