FIX: Notify group members when someone quotes or replies to their post. (#15295)

When a member set a group PM notification level to Normal, we didn't notify group members if someone quoted or replied to one of their posts.

app/services/post_alerter.rb

@@ -157,7 +157,7 @@ class PostAlerter
     # private messages
     if new_record
       if post.topic.private_message?
-        notify_pm_users(post, reply_to_user, notified)
+        notify_pm_users(post, reply_to_user, quoted_users, notified)
       elsif notify_about_reply?(post)
         notify_post_users(post, notified, new_record: new_record)
       end
@@ -582,9 +582,9 @@ class PostAlerter
   # TODO: Move to post-analyzer?
   # Returns a list of users who were quoted in the post
   def extract_quoted_users(post)
-    post.raw.scan(/\[quote=\"([^,]+),.+\"\]/).uniq.map do |m|
-      User.find_by("username_lower = :username AND id != :id", username: m.first.strip.downcase, id: post.user_id)
-    end.compact
+    usernames = post.raw.scan(/\[quote=\"([^,]+),.+\"\]/).uniq.map { |q| q.first.strip.downcase }
+
+    User.where.not(id: post.user_id).where(username_lower: usernames)
   end
 
   def extract_linked_users(post)
@@ -622,7 +622,7 @@ class PostAlerter
     users
   end
 
-  def notify_pm_users(post, reply_to_user, notified)
+  def notify_pm_users(post, reply_to_user, quoted_users, notified)
     return unless post.topic
 
     warn_if_not_sidekiq
@@ -653,11 +653,18 @@ class PostAlerter
     users.each do |user|
       case TopicUser.get(post.topic, user)&.notification_level
       when TopicUser.notification_levels[:watching]
-        # only create a notification when watching the group
-        create_notification(user, Notification.types[:private_message], post, skip_send_email_to: emails_to_skip_send)
+        create_pm_notification(user, post, emails_to_skip_send)
       when TopicUser.notification_levels[:tracking]
+        if is_replying?(user, reply_to_user, quoted_users)
+          create_pm_notification(user, post, emails_to_skip_send)
+        else
           notify_group_summary(user, post)
         end
+      when TopicUser.notification_levels[:regular]
+        if is_replying?(user, reply_to_user, quoted_users)
+          create_pm_notification(user, post, emails_to_skip_send)
+        end
+      end
     end
   end
 
@@ -842,4 +849,12 @@ class PostAlerter
       User.where(id: user_ids_batch).includes(:do_not_disturb_timings).each { |user| yield(user) }
     end
   end
+
+  def create_pm_notification(user, post, emails_to_skip_send)
+    create_notification(user, Notification.types[:private_message], post, skip_send_email_to: emails_to_skip_send)
+  end
+
+  def is_replying?(user, reply_to_user, quoted_users)
+    reply_to_user == user || quoted_users.include?(user)
+  end
 end

spec/services/post_alerter_spec.rb

@@ -125,6 +125,69 @@ describe PostAlerter do
         expect(message_data.dig(:last_notification, :notification, :data, :inbox_count)).to eq(starting_count + 1)
         expect(message_data[:unread_notifications]).to eq(1)
       end
+
+      it 'sends a PM notification when replying to a member tracking the topic' do
+        group.add(user1)
+
+        post = Fabricate(:post, topic: pm, user: user1)
+        TopicUser.change(user1.id, pm.id, notification_level: TopicUser.notification_levels[:tracking])
+
+        expect {
+          create_post_with_alerts(
+            raw: 'this is a reply to your post...', topic: pm, user: user2,
+            reply_to_post_number: post.post_number
+          )
+        }.to change(
+          user1.notifications.where(notification_type: Notification.types[:private_message]),
+          :count
+        ).by(1)
+      end
+
+      it 'notifies a group member if someone replies to their post' do
+        group.add(user1)
+
+        post = Fabricate(:post, topic: pm, user: user1)
+        TopicUser.change(user1.id, pm.id, notification_level: TopicUser.notification_levels[:regular])
+
+        expect {
+          create_post_with_alerts(
+            raw: 'this is a reply to your post...', topic: pm, user: user2,
+            reply_to_post_number: post.post_number
+          )
+        }.to change(user1.notifications, :count).by(1)
+      end
+
+      it 'nofies a group member if someone quotes their post' do
+        group.add(user1)
+
+        post = Fabricate(:post, topic: pm, user: user1)
+        TopicUser.change(user1.id, pm.id, notification_level: TopicUser.notification_levels[:regular])
+        quote_raw = <<~STRING
+          [quote="#{user1.username}, post:1, topic:#{pm.id}"]#{post.raw}[/quote]
+        STRING
+
+        expect {
+          create_post_with_alerts(
+            raw: quote_raw, topic: pm, user: user2,
+          )
+        }.to change(user1.notifications, :count).by(1)
+      end
+
+      it "Doesn't notify non-admin users when their post is quoted inside a whisper" do
+        admin = Fabricate(:admin)
+        group.add(admin)
+
+        TopicUser.change(user2.id, pm.id, notification_level: TopicUser.notification_levels[:regular])
+        quote_raw = <<~STRING
+          [quote="#{user2.username}, post:1, topic:#{pm.id}"]#{op.raw}[/quote]
+        STRING
+
+        expect {
+          create_post_with_alerts(
+            raw: quote_raw, topic: pm, user: admin, post_type: Post.types[:whisper]
+          )
+        }.to change(user2.notifications, :count).by(0)
+      end
     end
   end