From d857695d620da324457c56a2cd328b2ed441b04d Mon Sep 17 00:00:00 2001
From: Mat Moore <mwehtam@gmail.com>
Date: Mon, 5 Jan 2015 15:19:08 +0000
Subject: [PATCH] Vote buttons should be disabled while in use

Clicking quickly on up/down votes in forums generates a race condition
where the votes can continue going up or down (and I can get e.g. large
negative numbers). This is client-side; the server-side is not affected.

This is caused by safeAjax calling code (including updateWithUndo) not
handling the possible undefined return value. This is returned in the case
where the element that triggers the event is already disabled.

Corrected typo in DiscussionThreadView cleanup: @responseRequest -> @responsesRequest

Resolves TNL-1061
---
 AUTHORS                                       |  1 +
 .../coffee/spec/discussion/utils_spec.coffee  | 21 +++++++++++++++++++
 .../static/coffee/src/discussion/utils.coffee |  6 +++++-
 .../views/discussion_thread_view.coffee       |  2 +-
 4 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index 45b0c48603..1db15d22bb 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -195,3 +195,4 @@ Dino Cikatić <dcikatic@edx.org>
 Davorin Šego <dsego@edx.org>
 Marko Jevtić <mjevtic@edx.org>
 Ahsan Ulhaq <ahsan@edx.org>
+Mat Moore <mat@mooresoftware.co.uk>
diff --git a/common/static/coffee/spec/discussion/utils_spec.coffee b/common/static/coffee/spec/discussion/utils_spec.coffee
index e4285014e5..c456855e06 100644
--- a/common/static/coffee/spec/discussion/utils_spec.coffee
+++ b/common/static/coffee/spec/discussion/utils_spec.coffee
@@ -25,3 +25,24 @@ describe 'DiscussionUtil', ->
       # if the ajax call ends in failure, the model state should be reverted
       deferred.reject()
       expect(model.attributes).toEqual({hello: false, number: 42})
+
+    it "rolls back the changes if the associated element is disabled", ->
+      spyOn(DiscussionUtil, "safeAjax").andCallThrough()
+
+      model = new Backbone.Model({hello: false, number: 42})
+      updates = {hello: "world"}
+
+      # This is the element that is disabled/enabled while the ajax request is
+      # in progress
+      $elem = jasmine.createSpyObj('$elem', ['attr'])
+      $elem.attr.andReturn(true)
+
+      res = DiscussionUtil.updateWithUndo(model, updates, {foo: "bar", $elem:$elem}, "error message")
+
+      expect($elem.attr).toHaveBeenCalledWith("disabled")
+      expect(DiscussionUtil.safeAjax).toHaveBeenCalled()
+      expect(model.attributes).toEqual({hello: false, number: 42})
+
+      failed = false
+      res.fail(() => failed = true)
+      expect(failed).toBe(true);
diff --git a/common/static/coffee/src/discussion/utils.coffee b/common/static/coffee/src/discussion/utils.coffee
index 0d2b31fdfd..dd6e126e6f 100644
--- a/common/static/coffee/src/discussion/utils.coffee
+++ b/common/static/coffee/src/discussion/utils.coffee
@@ -134,8 +134,12 @@ class @DiscussionUtil
 
   @safeAjax: (params) ->
     $elem = params.$elem
+
     if $elem and $elem.attr("disabled")
-      return
+      deferred = $.Deferred()
+      deferred.reject()
+      return deferred.promise()
+
     params["url"] = URI(params["url"]).addSearch ajax: 1
     params["beforeSend"] = ->
       if $elem
diff --git a/common/static/coffee/src/discussion/views/discussion_thread_view.coffee b/common/static/coffee/src/discussion/views/discussion_thread_view.coffee
index 6df9807e3f..7b315571c3 100644
--- a/common/static/coffee/src/discussion/views/discussion_thread_view.coffee
+++ b/common/static/coffee/src/discussion/views/discussion_thread_view.coffee
@@ -127,7 +127,7 @@ if Backbone?
         $loading: elem
         takeFocus: true
         complete: =>
-          @responseRequest = null
+          @responsesRequest = null
         success: (data, textStatus, xhr) =>
           Content.loadContentInfos(data['annotated_content_info'])
           if @isQuestion()