feat(signaling): implement existing_users event for late joiners

app/modules/meeting/ws_router.py

@@ -74,6 +74,19 @@ async def signaling_websocket(
         sender_id=user_id,  # Don't echo back to the joiner themselves
     )
 
+    # Tell the new user about all existing users so they can update their UI immediately
+    participants = await MeetingStateService().get_participants(room_code)
+    existing_users = [
+        {
+            "user_id": pid,
+            "display_name": pstate.get("display_name", ""),
+            "role": pstate.get("role", "guest"),
+        }
+        for pid, pstate in participants.items()
+        if pid != user_id
+    ]
+    await websocket.send_json({"type": "existing_users", "users": existing_users})
+
     try:
         while True:
             data = await websocket.receive_text()

tests/meeting/test_ws_router.py

@@ -60,12 +60,27 @@ def mock_kafka_consumer():
         yield consumer
 
 
-@pytest.mark.usefixtures("mock_room_participant")
+@pytest.fixture
+def mock_meeting_state():
+    with patch(
+        "app.modules.meeting.ws_router.MeetingStateService"
+    ) as mock_service_class:
+        service = MagicMock()
+        service.get_participants = AsyncMock(return_value={})
+        mock_service_class.return_value = service
+        yield service
+
+
+@pytest.mark.usefixtures("mock_room_participant", "mock_meeting_state")
 def test_signaling_websocket(mock_connection_manager):
     # This will connect, send a text message, and then close
     with client.websocket_connect(
         "/api/v1/ws/signaling/room1?token=mock_token"
     ) as websocket:
+        # Consume the initial existing_users message
+        data = websocket.receive_json()
+        assert data["type"] == "existing_users"
+
         websocket.send_text(json.dumps({"type": "offer", "target_user_id": "user2"}))
         # The connection manager's send_to_user should be called