FIX: Notify on tag change. (#7119)

app/jobs/regular/notify_tag_change.rb

@@ -0,0 +1,15 @@
+require_dependency "post_alerter"
+
+module Jobs
+  class NotifyTagChange < Jobs::Base
+    def execute(args)
+      post = Post.find_by(id: args[:post_id])
+
+      if post&.topic
+        post_alerter = PostAlerter.new
+        post_alerter.notify_post_users(post, User.where(id: args[:notified_user_ids]))
+        post_alerter.notify_first_post_watchers(post, post_alerter.tag_watchers(post.topic))
+      end
+    end
+  end
+end

lib/post_revisor.rb

@@ -83,7 +83,14 @@ class PostRevisor
         tc.check_result(false)
         next
       end
-      tc.record_change('tags', prev_tags, tags) unless prev_tags.sort == tags.sort
+      if prev_tags.sort != tags.sort
+        tc.record_change('tags', prev_tags, tags)
+        DB.after_commit do
+          post = tc.topic.ordered_posts.first
+          notified_user_ids = [post.user_id, post.last_editor_id].uniq
+          Jobs.enqueue(:notify_tag_change, post_id: post.id, notified_user_ids: notified_user_ids)
+        end
+      end
     end
   end
 

spec/services/post_alerter_spec.rb

@@ -926,6 +926,29 @@ describe PostAlerter do
         expect(events).to include(event_name: :before_create_notifications_for_users, params: [[user], post])
       end
     end
+
+    context "on change" do
+      let(:user) { Fabricate(:user) }
+      let(:other_tag) { Fabricate(:tag) }
+      let(:watched_tag) { Fabricate(:tag) }
+      let(:post) { Fabricate(:post) }
+
+      before do
+        SiteSetting.tagging_enabled = true
+        SiteSetting.queue_jobs = false
+      end
+
+      it "triggers a notification" do
+        TagUser.change(user.id, watched_tag.id, TagUser.notification_levels[:watching_first_post])
+        expect(user.notifications.where(notification_type: Notification.types[:watching_first_post]).count).to eq(0)
+
+        PostRevisor.new(post).revise!(Fabricate(:user), tags: [other_tag.name, watched_tag.name])
+        expect(user.notifications.where(notification_type: Notification.types[:watching_first_post]).count).to eq(1)
+
+        PostRevisor.new(post).revise!(Fabricate(:user), tags: [watched_tag.name, other_tag.name])
+        expect(user.notifications.where(notification_type: Notification.types[:watching_first_post]).count).to eq(1)
+      end
+    end
   end
 
   describe '#extract_linked_users' do