mentions: process mentions added in an edit (fix #2736)

app/logical/mentionable.rb

@@ -8,7 +8,8 @@ module Mentionable
     def mentionable(options = {})
       @mentionable_options = options
 
-      after_create :queue_mention_messages
+      message_field = mentionable_option(:message_field)
+      after_save :queue_mention_messages, if: :"#{message_field}_changed?"
     end
 
     def mentionable_option(key)
@@ -17,8 +18,11 @@ module Mentionable
   end
 
   def queue_mention_messages
-    text = read_attribute(self.class.mentionable_option(:message_field))
-    names = DText.parse_mentions(text)
+    message_field = self.class.mentionable_option(:message_field)
+    text = send(message_field)
+    text_was = send("#{message_field}_was")
+
+    names = DText.parse_mentions(text) - DText.parse_mentions(text_was)
 
     names.uniq.each do |name|
       body  = self.instance_exec(name, &self.class.mentionable_option(:body))

test/unit/comment_test.rb

@@ -20,6 +20,21 @@ class CommentTest < ActiveSupport::TestCase
         Danbooru.config.stubs(:member_comment_time_threshold).returns(1.week.from_now)
       end
 
+      context "added in an edit" do
+        should "dmail the added user" do
+          @user1 = FactoryGirl.create(:user)
+          @user2 = FactoryGirl.create(:user)
+          @comment = FactoryGirl.create(:comment, :post_id => @post.id, :body => "@#{@user1.name}")
+
+          assert_no_difference("@user1.dmails.count") do
+            assert_difference("@user2.dmails.count") do
+              @comment.body = "@#{@user1.name} @#{@user2.name}"
+              @comment.save
+            end
+          end
+        end
+      end
+
       context "in a quote block" do
         setup do
           @user2 = FactoryGirl.create(:user, :created_at => 2.weeks.ago)