FIX: Serialize channel title for DMs (#90)

app/serializers/ai_chat_channel_serializer.rb

@@ -1,5 +1,11 @@
 # frozen_string_literal: true
 
 class AiChatChannelSerializer < ApplicationSerializer
-  attributes :id, :chatable, :chatable_type, :chatable_url, :title, :slug
+  attributes :id, :chatable, :chatable_type, :chatable_url, :slug
+
+  def title
+    # Display all participants for a DM.
+    # For category channels, the argument is ignored.
+    object.title(nil)
+  end
 end

spec/serializers/ai_chat_channel_serializer_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+RSpec.describe AiChatChannelSerializer do
+  fab!(:admin) { Fabricate(:admin) }
+
+  describe "#title" do
+    context "when the channel is a DM" do
+      fab!(:dm_channel) { Fabricate(:direct_message_channel) }
+
+      it "display every participant" do
+        serialized = described_class.new(dm_channel, scope: Guardian.new(admin), root: nil)
+
+        expect(serialized.title).to eq(dm_channel.title(nil))
+      end
+    end
+
+    context "when the channel is a regular one" do
+      fab!(:channel) { Fabricate(:chat_channel) }
+
+      it "displays the category title" do
+        serialized = described_class.new(channel, scope: Guardian.new(admin), root: nil)
+
+        expect(serialized.title).to eq(channel.title)
+      end
+    end
+  end
+end