FIX: On tag change notify only users watching the tag. (#7707)

app/jobs/regular/notify_tag_change.rb

@@ -9,7 +9,6 @@ module Jobs
 
       if post&.topic&.visible?
         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

lib/post_revisor.rb

@@ -94,8 +94,7 @@ class PostRevisor
         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)
+          Jobs.enqueue(:notify_tag_change, post_id: post.id)
         end
       end
     end

spec/services/post_alerter_spec.rb

@@ -989,15 +989,16 @@ describe PostAlerter do
         SiteSetting.tagging_enabled = true
         Jobs.run_immediately!
         TagUser.change(user.id, watched_tag.id, TagUser.notification_levels[:watching_first_post])
+        TopicUser.change(Fabricate(:user).id, post.topic.id, notification_level: TopicUser.notification_levels[:watching])
       end
 
       it "triggers a notification" do
         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 { PostRevisor.new(post).revise!(Fabricate(:user), tags: [other_tag.name, watched_tag.name]) }.to change { Notification.count }.by(1)
         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 { PostRevisor.new(post).revise!(Fabricate(:user), tags: [watched_tag.name, other_tag.name]) }.to change { Notification.count }.by(0)
         expect(user.notifications.where(notification_type: Notification.types[:watching_first_post]).count).to eq(1)
       end