FIX: Missing notification for watching first post users when topic is recategorized.

https://meta.discourse.org/t/not-receiving-notifications-for-announcements/87275/2?u=tgxworld

app/models/topic.rb

@@ -677,10 +677,16 @@ SQL
         post = self.ordered_posts.first
 
         if post
-          PostAlerter.new.notify_post_users(
+          post_alerter = PostAlerter.new
+
+          post_alerter.notify_post_users(
             post,
             [post.user, post.last_editor].uniq
           )
+
+          post_alerter.notify_first_post_watchers(
+            post, post_alerter.category_watchers(self)
+          )
         end
       end
 

app/services/post_alerter.rb

@@ -101,28 +101,31 @@ class PostAlerter
       topic = post.topic
 
       if topic.present?
-        cat_watchers = topic.category_users
-          .where(notification_level: CategoryUser.notification_levels[:watching_first_post])
-          .pluck(:user_id)
-
-        tag_watchers = topic.tag_users
-          .where(notification_level: TagUser.notification_levels[:watching_first_post])
-          .pluck(:user_id)
-
-        group_ids = topic.allowed_groups.pluck(:group_id)
-
-        group_watchers = GroupUser.where(
-          group_id: group_ids,
-          notification_level: GroupUser.notification_levels[:watching_first_post]
-        ).pluck(:user_id)
-
-        watchers = [cat_watchers, tag_watchers, group_watchers].flatten
-
+        watchers = category_watchers(topic) + tag_watchers(topic) + group_watchers(topic)
         notify_first_post_watchers(post, watchers)
       end
     end
   end
 
+  def group_watchers(topic)
+    GroupUser.where(
+      group_id: topic.allowed_groups.pluck(:group_id),
+      notification_level: GroupUser.notification_levels[:watching_first_post]
+    ).pluck(:user_id)
+  end
+
+  def tag_watchers(topic)
+    topic.tag_users
+      .where(notification_level: TagUser.notification_levels[:watching_first_post])
+      .pluck(:user_id)
+  end
+
+  def category_watchers(topic)
+    topic.category_users
+      .where(notification_level: CategoryUser.notification_levels[:watching_first_post])
+      .pluck(:user_id)
+  end
+
   def notify_first_post_watchers(post, user_ids)
     return if user_ids.blank?
     user_ids.uniq!

spec/models/topic_spec.rb

@@ -1212,7 +1212,7 @@ describe Topic do
           expect(category.reload.topic_count).to eq(0)
         end
 
-        describe 'user that watching the new category' do
+        describe 'user that is watching the new category' do
           it 'should generate the notification for the topic' do
             topic.posts << Fabricate(:post)
 
@@ -1222,16 +1222,31 @@ describe Topic do
               new_category.id
             )
 
+            another_user = Fabricate(:user)
+
+            CategoryUser.set_notification_level_for_category(
+              another_user,
+              CategoryUser::notification_levels[:watching_first_post],
+              new_category.id
+            )
+
             expect do
               topic.change_category_to_id(new_category.id)
-            end.to change { Notification.count }.by(1)
+            end.to change { Notification.count }.by(2)
 
-            notification = Notification.last
+            expect(Notification.where(
+              user_id: user.id,
+              topic_id: topic.id,
+              post_number: 1,
+              notification_type: Notification.types[:posted]
+            ).exists?).to eq(true)
 
-            expect(notification.notification_type).to eq(Notification.types[:posted])
-            expect(notification.topic_id).to eq(topic.id)
-            expect(notification.user_id).to eq(user.id)
-            expect(notification.post_number).to eq(1)
+            expect(Notification.where(
+              user_id: another_user.id,
+              topic_id: topic.id,
+              post_number: 1,
+              notification_type: Notification.types[:watching_first_post]
+            ).exists?).to eq(true)
           end
         end