FIX: Error when publishing TopicTrackingState updates for certain topics (#19812)

When a topic belongs to category that is read restricted but permission
has not been granted to any groups, publishing ceratin topic tracking state
updates for the topic will result in the `MessageBus::InvalidMessageTarget` error being raised
because we're passing `nil` to `group_ids` which is not support by
MessageBus.

This commit ensures that for said category above, we will publish the
updates to the admin groups.

app/models/topic_tracking_state.rb

@@ -53,7 +53,7 @@ class TopicTrackingState
 
     message = { topic_id: topic.id, message_type: NEW_TOPIC_MESSAGE_TYPE, payload: payload }
 
-    group_ids = topic.category && topic.category.secure_group_ids
+    group_ids = secure_category_group_ids(topic)
 
     MessageBus.publish("/new", message.as_json, group_ids: group_ids)
     publish_read(topic.id, 1, topic.user)
@@ -84,8 +84,9 @@ class TopicTrackingState
       if whisper
         [Group::AUTO_GROUPS[:staff], *SiteSetting.whispers_allowed_group_ids]
       else
-        topic.category && topic.category.secure_group_ids
+        secure_category_group_ids(topic)
       end
+
     MessageBus.publish("/latest", message.as_json, group_ids: group_ids)
   end
 
@@ -171,7 +172,7 @@ class TopicTrackingState
   end
 
   def self.publish_recover(topic)
-    group_ids = topic.category && topic.category.secure_group_ids
+    group_ids = secure_category_group_ids(topic)
 
     message = { topic_id: topic.id, message_type: RECOVER_MESSAGE_TYPE }
 
@@ -179,7 +180,7 @@ class TopicTrackingState
   end
 
   def self.publish_delete(topic)
-    group_ids = topic.category && topic.category.secure_group_ids
+    group_ids = secure_category_group_ids(topic)
 
     message = { topic_id: topic.id, message_type: DELETE_MESSAGE_TYPE }
 
@@ -187,7 +188,7 @@ class TopicTrackingState
   end
 
   def self.publish_destroy(topic)
-    group_ids = topic.category && topic.category.secure_group_ids
+    group_ids = secure_category_group_ids(topic)
 
     message = { topic_id: topic.id, message_type: DESTROY_MESSAGE_TYPE }
 
@@ -546,4 +547,15 @@ class TopicTrackingState
     opts = { readers_count: post.readers_count, reader_id: user_id }
     post.publish_change_to_clients!(:read, opts)
   end
+
+  def self.secure_category_group_ids(topic)
+    ids = topic&.category&.secure_group_ids
+
+    if ids.blank?
+      [Group::AUTO_GROUPS[:admin]]
+    else
+      ids
+    end
+  end
+  private_class_method :secure_category_group_ids
 end

spec/models/topic_tracking_state_spec.rb

@@ -10,7 +10,26 @@ RSpec.describe TopicTrackingState do
   fab!(:private_message_post) { Fabricate(:private_message_post) }
   let(:private_message_topic) { private_message_post.topic }
 
-  describe "#publish_latest" do
+  fab!(:read_restricted_category) { Fabricate(:category, read_restricted: true) }
+  fab!(:read_restricted_topic) { Fabricate(:topic, category: read_restricted_category) }
+
+  describe ".publish_new" do
+    it "should publish message only to admin group when category is read restricted but no groups have been granted access" do
+      message =
+        MessageBus
+          .track_publish("/new") { described_class.publish_new(read_restricted_topic) }
+          .first
+
+      data = message.data
+
+      expect(data["topic_id"]).to eq(read_restricted_topic.id)
+      expect(data["message_type"]).to eq(described_class::NEW_TOPIC_MESSAGE_TYPE)
+      expect(message.group_ids).to contain_exactly(Group::AUTO_GROUPS[:admin])
+      expect(message.user_ids).to eq(nil)
+    end
+  end
+
+  describe ".publish_latest" do
     it "can correctly publish latest" do
       message = MessageBus.track_publish("/latest") { described_class.publish_latest(topic) }.first
 
@@ -36,6 +55,20 @@ RSpec.describe TopicTrackingState do
       expect(message.group_ids).to contain_exactly(whisperers_group.id, Group::AUTO_GROUPS[:staff])
     end
 
+    it "should publish message only to admin group when category is read restricted but no groups have been granted access" do
+      message =
+        MessageBus
+          .track_publish("/latest") { described_class.publish_latest(read_restricted_topic) }
+          .first
+
+      data = message.data
+
+      expect(data["topic_id"]).to eq(read_restricted_topic.id)
+      expect(data["message_type"]).to eq(described_class::LATEST_MESSAGE_TYPE)
+      expect(message.group_ids).to contain_exactly(Group::AUTO_GROUPS[:admin])
+      expect(message.user_ids).to eq(nil)
+    end
+
     describe "private message" do
       it "should not publish any message" do
         messages =
@@ -699,4 +732,52 @@ RSpec.describe TopicTrackingState do
       expect(state.map(&:topic_id)).to contain_exactly(topic.id)
     end
   end
+
+  describe ".publish_recover" do
+    it "should publish message only to admin group when category is read restricted but no groups have been granted access" do
+      message =
+        MessageBus
+          .track_publish("/recover") { described_class.publish_recover(read_restricted_topic) }
+          .first
+
+      data = message.data
+
+      expect(data["topic_id"]).to eq(read_restricted_topic.id)
+      expect(data["message_type"]).to eq(described_class::RECOVER_MESSAGE_TYPE)
+      expect(message.group_ids).to contain_exactly(Group::AUTO_GROUPS[:admin])
+      expect(message.user_ids).to eq(nil)
+    end
+  end
+
+  describe ".publish_delete" do
+    it "should publish message only to admin group when category is read restricted but no groups have been granted access" do
+      message =
+        MessageBus
+          .track_publish("/delete") { described_class.publish_delete(read_restricted_topic) }
+          .first
+
+      data = message.data
+
+      expect(data["topic_id"]).to eq(read_restricted_topic.id)
+      expect(data["message_type"]).to eq(described_class::DELETE_MESSAGE_TYPE)
+      expect(message.group_ids).to contain_exactly(Group::AUTO_GROUPS[:admin])
+      expect(message.user_ids).to eq(nil)
+    end
+  end
+
+  describe ".publish_destroy" do
+    it "should publish message only to admin group when category is read restricted but no groups have been granted access" do
+      message =
+        MessageBus
+          .track_publish("/destroy") { described_class.publish_destroy(read_restricted_topic) }
+          .first
+
+      data = message.data
+
+      expect(data["topic_id"]).to eq(read_restricted_topic.id)
+      expect(data["message_type"]).to eq(described_class::DESTROY_MESSAGE_TYPE)
+      expect(message.group_ids).to contain_exactly(Group::AUTO_GROUPS[:admin])
+      expect(message.user_ids).to eq(nil)
+    end
+  end
 end