fix: initialize batch_id before try block in start_processing to prevent UnboundLocalError

Agent-Logs-Url: https://github.com/microsoft/Modernize-your-code-solution-accelerator/sessions/1182bdcf-25b8-4af7-b0e9-da0938566ee0

Co-authored-by: Abdul-Microsoft <192570837+Abdul-Microsoft@users.noreply.github.com>

Author: Copilot

src/backend/api/api_routes.py

@@ -91,6 +91,7 @@ async def start_processing(request: Request):
       500:
         description: Internal server error
     """
+    batch_id = None
     try:
         payload = await request.json()
         batch_id = payload.get("batch_id")
@@ -113,7 +114,10 @@ async def start_processing(request: Request):
             "message": "Files processed",
         }
     except Exception as e:
-        track_event_if_configured("ProcessingFailed", {"batch_id": batch_id, "error": str(e)})
+        event_data = {"error": str(e)}
+        if batch_id is not None:
+            event_data["batch_id"] = batch_id
+        track_event_if_configured("ProcessingFailed", event_data)
         record_exception_to_trace(e)
         raise HTTPException(status_code=500, detail=str(e)) from e
 

src/tests/backend/api/api_routes_test.py

@@ -138,6 +138,22 @@ async def test_start_processing_exception(self, mock_process_batch, mock_track_e
                 await start_processing(mock_request)
             assert exc_info.value.status_code == 500
 
+    @pytest.mark.asyncio
+    async def test_start_processing_json_parse_error(self, mock_track_event):
+        """Test processing start when request.json() raises before batch_id is assigned."""
+        mock_request = AsyncMock()
+        mock_request.json = AsyncMock(side_effect=Exception("Invalid JSON"))
+
+        with patch("backend.api.api_routes.record_exception_to_trace"):
+            with pytest.raises(HTTPException) as exc_info:
+                await start_processing(mock_request)
+            assert exc_info.value.status_code == 500
+            # batch_id should not be in the telemetry event data when it was never assigned
+            called_args = mock_track_event.call_args
+            assert called_args is not None
+            event_data = called_args[0][1]
+            assert "batch_id" not in event_data
+
 
 class TestDownloadFiles:
     """Tests for download_files endpoint."""