announcements: remove delayed posting date if delay unchecked

fixes CNVS-7343

test plan:
  * create a discussion topic with a delayed posting date
  * edit the topic, uncheck delay, and save
  * verify that the topic is no longer delayed

Change-Id: Iaaba7c2bdfbd1e8ce196c937d4917fc2470cbb6c
Reviewed-on: https://gerrit.instructure.com/23957
QA-Review: Cam Theriault <cam@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Zach Pendleton <zachp@instructure.com>
Product-Review: Zach Pendleton <zachp@instructure.com>

app/coffeescripts/views/DiscussionTopics/EditView.coffee

@@ -202,6 +202,8 @@ htmlEscape, DiscussionTopic, Announcement, Assignment, $, preventDefault, Missin
     )
 
     validateBeforeSave: (data, errors) =>
+      if data.delay_posting == "0"
+        data.delayed_post_at = null
       if @isTopic() && data.set_assignment is '1'
         if @assignmentGroupSelector?
           errors = @assignmentGroupSelector.validateBeforeSave(data, errors)

spec/selenium/announcements_spec.rb

@@ -284,6 +284,18 @@ describe "announcements" do
       f('.discussion-fyi').should include_text('This topic will not be visible')
     end
 
+    it "should remove delayed_post_at when unchecking delay_posting" do
+      topic = announcement_model(:title => @topic_title, :user => @user, :delayed_post_at => 10.days.ago)
+      get "/courses/#{@course.id}/announcements/#{topic.id}"
+      expect_new_page_load { f(".edit-btn").click }
+
+      f('input[type=checkbox][name="delay_posting"]').click
+      expect_new_page_load { f('.form-actions button[type=submit]').click }
+
+      topic.reload
+      topic.delayed_post_at.should be_nil
+    end
+
     it "should have a teacher add a new entry to its own announcement" do
       pending "delayed jobs"
       create_announcement