FIX: handle thread participants limit on the frontend (#23839)

Workaround for an issue we are experiencing on thread index frontend where thread loads participants correctly (up to 10), then refreshes the threads and then limits to 3 participants.

There is an issue with storing threads for the main channel view and the thread list in the same store so handling the max participants on the frontend is a workaround until channel.threadsManager is updated.

I've adjusted the tests to handle the additional data being returned from ThreadParticipantQuery.

plugins/chat/app/queries/chat/thread_participant_query.rb

@@ -17,10 +17,12 @@ module Chat
   # and if there is a delay in updating them based on message
   # count it is not a big deal.
   class ThreadParticipantQuery
+    MAX_PARTICIPANTS = 10
+
     # @param thread_ids [Array<Integer>] The IDs of the threads to query.
     # @param preview [Boolean] Determines the number of participants to return.
     # @return [Hash<Integer, Hash>] A hash of thread IDs to participant data.
-    def self.call(thread_ids:, preview: true)
+    def self.call(thread_ids:)
       return {} if thread_ids.blank?
 
       # We only want enough data for BasicUserSerializer, since the participants
@@ -64,8 +66,6 @@ module Chat
           hash
         end
 
-      total_participants = preview ? 2 : 9
-
       thread_participants = {}
       thread_participant_stats.each do |thread_participant_stat|
         thread_id = thread_participant_stat.thread_id
@@ -75,7 +75,7 @@ module Chat
 
         # If we want to return more of the top N users in the thread we
         # can just increase the number here.
-        if thread_participants[thread_id][:users].length < total_participants &&
+        if thread_participants[thread_id][:users].length < (MAX_PARTICIPANTS - 1) &&
              thread_participant_stat.user_id != most_recent_participants[thread_id][:id]
           thread_participants[thread_id][:users].push(
             {

plugins/chat/app/services/chat/lookup_channel_threads.rb

@@ -135,8 +135,7 @@ module Chat
     end
 
     def fetch_participants(threads:, **)
-      context.participants =
-        ::Chat::ThreadParticipantQuery.call(thread_ids: threads.map(&:id), preview: false)
+      context.participants = ::Chat::ThreadParticipantQuery.call(thread_ids: threads.map(&:id))
     end
 
     def build_load_more_url(contract:, **)

plugins/chat/assets/javascripts/discourse/components/chat/thread/participants.gjs

@@ -37,11 +37,17 @@ export default class ChatThreadParticipants extends Component {
   }
 
   get participantsUsers() {
+    const users = this.args.thread.preview.participantUsers;
+
     if (this.includeOriginalMessageUser) {
-      return this.args.thread.preview.participantUsers;
+      if (users.length > 3) {
+        return users.slice(0, 2).concat(users[users.length - 1]);
+      } else {
+        return users;
+      }
     }
 
-    return this.args.thread.preview.participantUsers.filter((user) => {
+    return users.filter((user) => {
       return user.id !== this.args.thread.originalMessage.user.id;
     });
   }

plugins/chat/spec/queries/chat/thread_participant_query_spec.rb

@@ -35,16 +35,15 @@ RSpec.describe Chat::ThreadParticipantQuery do
       )
     end
 
-    it "does not return more than 3 thread participants by default" do
-      thread_1.add(Fabricate(:user))
+    it "returns up to 10 thread participants" do
       result = described_class.call(thread_ids: [thread_1.id])
-      expect(result[thread_1.id][:users].length).to eq(3)
+      expect(result[thread_1.id][:users].length).to eq(4)
     end
 
     it "calculates the top messagers in a thread as well as the last messager" do
       result = described_class.call(thread_ids: [thread_1.id, thread_2.id])
-      expect(result[thread_1.id][:users].map { |u| u[:id] }).to eq(
-        [user_1.id, user_2.id, user_3.id],
+      expect(result[thread_1.id][:users].map { |u| u[:id] }).to match_array(
+        [thread_1.original_message_user_id, user_1.id, user_2.id, user_3.id],
       )
     end
 
@@ -82,8 +81,8 @@ RSpec.describe Chat::ThreadParticipantQuery do
       Fabricate(:chat_message, thread: thread_2, user: user_2)
       Fabricate(:chat_message, thread: thread_2, user: user_2)
       result = described_class.call(thread_ids: [thread_1.id, thread_2.id])
-      expect(result[thread_1.id][:users].map { |u| u[:id] }).to eq(
-        [user_1.id, user_2.id, user_3.id],
+      expect(result[thread_1.id][:users].map { |u| u[:id] }).to match_array(
+        [thread_1.original_message_user_id, user_1.id, user_2.id, user_3.id],
       )
       expect(result[thread_2.id][:users].map { |u| u[:id] }).to eq(
         [thread_2.original_message_user_id, user_2.id],
@@ -119,11 +118,11 @@ RSpec.describe Chat::ThreadParticipantQuery do
       end
     end
 
-    it "does not return more than 10 thread participants when preview is false" do
+    it "does not return more than 10 thread participants" do
       other_user = Fabricate(:user)
       thread_3.add(other_user)
       Fabricate(:chat_message, thread: thread_3, user: other_user)
-      result = described_class.call(thread_ids: [thread_3.id], preview: false)
+      result = described_class.call(thread_ids: [thread_3.id])
       expect(result[thread_3.id][:users].length).to eq(10)
     end
   end