FIX: stuck notification for mentions within threads (#30546)

For mentions within threads, the mentioned user can experience a stuck notification. This is due to thread memberships only being created for users who interact with a thread. Without the membership we cannot track if the message containing the mention was read by the user.

The solution to this explored in this PR is:

- auto add memberships for mentioned users (only direct mentions for performance reasons).
- update channel/thread unread queries to check notification read status AND thread membership last read message id when counting mentions.

Previously the mention count would remain until the user notification (containing the mention) was read. However this only happens if the user clicks the notification or clicks dismiss all notifications. When a user navigated to the thread without clicking the notification, the green/urgent badge on chat would remain even after a hard page refresh.

plugins/chat/app/models/chat/message.rb

@@ -381,6 +381,10 @@ module Chat
       new_mentions = parsed_mentions.direct_mentions.pluck(:id)
       delete_mentions("Chat::UserMention", old_mentions - new_mentions)
       insert_mentions("Chat::UserMention", new_mentions - old_mentions)
+
+      # add users to threads when they are mentioned to track read status
+      return if new_mentions.empty? || !in_thread?
+      User.where(id: new_mentions).each { |user| thread.add(user, notification_level: :normal) }
     end
   end
 end

plugins/chat/app/queries/chat/channel_unreads_query.rb

@@ -37,15 +37,17 @@ module Chat
         (
           SELECT COUNT(*) AS mention_count
           FROM notifications
-          INNER JOIN user_chat_channel_memberships ON user_chat_channel_memberships.user_id = :user_id
+          INNER JOIN user_chat_channel_memberships AS uccm ON uccm.user_id = :user_id
           INNER JOIN chat_messages ON (data::json->>'chat_message_id')::bigint = chat_messages.id
           LEFT JOIN chat_threads ON chat_threads.id = chat_messages.thread_id
+          LEFT JOIN user_chat_thread_memberships AS uctm ON uctm.thread_id = chat_messages.thread_id AND uctm.user_id = :user_id
           WHERE NOT read
-          AND user_chat_channel_memberships.chat_channel_id = memberships.chat_channel_id
+          AND uccm.chat_channel_id = memberships.chat_channel_id
           AND notifications.user_id = :user_id
           AND notifications.notification_type = :notification_type_mention
-          AND (data::json->>'chat_message_id')::bigint > COALESCE(user_chat_channel_memberships.last_read_message_id, 0)
           AND (data::json->>'chat_channel_id')::bigint = memberships.chat_channel_id
+          AND (((chat_messages.thread_id IS NULL OR chat_messages.id = chat_threads.original_message_id) AND chat_messages.id > COALESCE(uccm.last_read_message_id, 0))
+          OR (chat_messages.thread_id IS NOT NULL AND uctm.id IS NOT NULL AND chat_messages.id > COALESCE(uctm.last_read_message_id, 0)))
         ) AS mention_count,
         (
           SELECT COUNT(*) AS watched_threads_unread_count

plugins/chat/app/queries/chat/thread_unreads_query.rb

@@ -64,16 +64,17 @@ module Chat
           FROM notifications
           INNER JOIN chat_messages ON chat_messages.id = (data::json->>'chat_message_id')::bigint
           INNER JOIN chat_channels ON chat_channels.id = chat_messages.chat_channel_id
-          INNER JOIN user_chat_channel_memberships ON user_chat_channel_memberships.chat_channel_id = chat_messages.chat_channel_id
-          LEFT JOIN chat_threads ON chat_threads.id = chat_messages.thread_id
+          INNER JOIN user_chat_channel_memberships AS uccm ON uccm.chat_channel_id = chat_messages.chat_channel_id
+          INNER JOIN user_chat_thread_memberships AS uctm ON uctm.thread_id = chat_messages.thread_id AND uctm.user_id = :user_id
           WHERE NOT read
           AND notifications.user_id = :user_id
           AND notifications.notification_type = :notification_type_mention
-          AND user_chat_channel_memberships.user_id = :user_id
+          AND uccm.user_id = :user_id
           AND chat_channels.threading_enabled
           AND chat_messages.deleted_at IS NULL
           AND chat_messages.thread_id = memberships.thread_id
-          AND NOT user_chat_channel_memberships.muted
+          AND (uctm.id IS NOT NULL AND chat_messages.id > COALESCE(uctm.last_read_message_id, 0))
+          AND NOT uccm.muted
         ) AS mention_count,
         (
           SELECT COUNT(*) AS watched_threads_unread_count

plugins/chat/assets/javascripts/discourse/components/chat-channel-unread-indicator.gjs

@@ -39,7 +39,7 @@ export default class ChatChannelUnreadIndicator extends Component {
   }
 
   get urgentBadgeCount() {
-    let totalCount = this.urgentCount;
+    const totalCount = this.urgentCount;
     return totalCount > MAX_UNREAD_COUNT ? `${MAX_UNREAD_COUNT}+` : totalCount;
   }
 

plugins/chat/assets/javascripts/discourse/components/chat/header/icon/unread-indicator.gjs

@@ -69,7 +69,7 @@ export default class ChatHeaderIconUnreadIndicator extends Component {
   }
 
   get urgentCountLabel() {
-    let totalCount = this.onlyMentions ? this.mentionCount : this.urgentCount;
+    const totalCount = this.onlyMentions ? this.mentionCount : this.urgentCount;
     return totalCount > MAX_UNREAD_COUNT ? `${MAX_UNREAD_COUNT}+` : totalCount;
   }
 

plugins/chat/spec/models/chat/message_spec.rb

@@ -787,6 +787,22 @@ describe Chat::Message do
         expect(message.user_mentions.pluck(:target_id)).to match_array(already_mentioned)
         expect(message.user_mentions.pluck(:id)).to include(*existing_mention_ids) # the mentions weren't recreated
       end
+
+      it "creates thread memberships for mentioned users when replying to a thread" do
+        thread = Fabricate(:chat_thread)
+        thread_message =
+          Fabricate(
+            :chat_message,
+            chat_channel: thread.channel,
+            thread: thread,
+            message: "cc @#{user3.username} and @#{user4.username}",
+          )
+
+        thread_message.cook
+        thread_message.upsert_mentions
+
+        expect(thread.user_chat_thread_memberships.pluck(:user_id)).to include(user3.id, user4.id)
+      end
     end
 
     context "with group mentions" do

plugins/chat/spec/queries/chat/channel_unreads_query_spec.rb

@@ -210,7 +210,7 @@ describe Chat::ChannelUnreadsQuery do
     end
 
     context "for unread mentions in a thread" do
-      fab!(:thread_om) { Fabricate(:chat_message, chat_channel: channel_1) }
+      fab!(:thread_om) { Fabricate(:chat_message, chat_channel: channel_1, user: current_user) }
       fab!(:thread) { Fabricate(:chat_thread, channel: channel_1, original_message: thread_om) }
 
       it "does include the original message in the mention count" do
@@ -230,6 +230,7 @@ describe Chat::ChannelUnreadsQuery do
         thread_message_2 = Fabricate(:chat_message, chat_channel: channel_1, thread: thread)
         create_mention(thread_message_1, channel_1)
         create_mention(thread_message_2, channel_1)
+
         expect(query.first).to eq(
           {
             mention_count: 2,