FIX: Make sure marking channels read propagates to all tabs (#20802)

Instead of just marking the state read in JS for each channel
after the AJAX call, we can instead just rely on the MessageBus
user-tracking-state chat channel, and publish the state to all
the channels affected in MarkAllUserChannelsRead. This will make
it so the blue dots for the channels are cleared across all tabs.

plugins/chat/app/services/chat/mark_all_user_channels_read.rb

@@ -17,6 +17,7 @@ module Chat
     transaction do
       step :update_last_read_message_ids
       step :mark_associated_mentions_as_read
+      step :publish_user_tracking_state
     end
 
     private
@@ -51,5 +52,15 @@ module Chat
         channel_ids: updated_memberships.map(&:channel_id),
       )
     end
+
+    def publish_user_tracking_state(guardian:, updated_memberships:, **)
+      updated_memberships.each do |membership|
+        Chat::Publisher.publish_user_tracking_state(
+          guardian.user,
+          membership.channel_id,
+          membership.last_read_message_id,
+        )
+      end
+    end
   end
 end

plugins/chat/assets/javascripts/discourse/services/chat-channels-manager.js

@@ -85,17 +85,8 @@ export default class ChatChannelsManager extends Service {
 
   @debounce(300)
   async markAllChannelsRead() {
-    return this.chatApi.markAllChannelsAsRead().then((response) => {
+    // The user tracking state for each channel marked read will be propagated by MessageBus
-      response.updated_memberships.forEach((membership) => {
+    return this.chatApi.markAllChannelsAsRead();
-        let channel = this.channels.findBy("id", membership.channel_id);
-        if (channel) {
-          channel.currentUserMembership.unread_count = 0;
-          channel.currentUserMembership.unread_mentions = 0;
-          channel.currentUserMembership.last_read_message_id =
-            membership.last_read_message_id;
-        }
-      });
-    });
   }
 
   remove(model) {

plugins/chat/spec/services/chat/mark_all_user_channels_read_spec.rb

@@ -128,6 +128,13 @@ RSpec.describe Chat::MarkAllUserChannelsRead do
           ).count
         }.by(-2)
       end
+
+      it "publishes tracking state for all affected channels" do
+        messages = MessageBus.track_publish { result }
+        expect(
+          messages.select { |m| m.channel == "/chat/user-tracking-state/#{current_user.id}" }.count,
+        ).to eq(3)
+      end
     end
   end
 end