ETL-772: Fix/dlq empty response

VERSION

@@ -1 +1 @@
-3.7.2
+3.7.3

src/glassflow/etl/dlq.py

@@ -40,9 +40,9 @@ def consume(self, batch_size: int = 100) -> List[Dict[str, Any]]:
                 "GET", f"{self.endpoint}/consume", params={"batch_size": batch_size}
             )
             response.raise_for_status()
-            if response.status_code != 204:
-                return response.json()
-            return []
+            if response.status_code == 204 or not response.content:
+                return []
+            return response.json()
         except errors.UnprocessableContentError as e:
             raise InvalidBatchSizeError(
                 f"Invalid batch size: batch size should be larger than 1 "

src/glassflow/etl/models/stateless_transformation.py

@@ -16,7 +16,9 @@ class Transformation(BaseModel):
 
 
 class ExpressionConfig(BaseModel):
-    transform: List[Transformation] = Field(description="The transformation expression")
+    transform: Optional[List[Transformation]] = Field(
+        description="The transformation expression", default=None
+    )
 
 
 class StatelessTransformationConfig(BaseModel):
@@ -50,6 +52,11 @@ def validate(self) -> "StatelessTransformationConfig":
                 raise ValueError(
                     "config is required when stateless transformation is enabled"
                 )
+            else:
+                if not self.config.transform:
+                    raise ValueError(
+                        "transform is required when stateless transformation is enabled"
+                    )
         return self
 
     def update(

tests/test_dlq.py

@@ -33,6 +33,45 @@ def test_consume_success(self, dlq, mock_success):
                 {"id": "msg2", "content": "test message 2"},
             ]
 
+    def test_consume_returns_empty_list_when_no_messages(self, dlq, mock_success):
+        """Test DLQ consume returns empty list when there are no messages to consume."""
+        with mock_success(json_payloads=[[]]) as mock_get:
+            result = dlq.consume(batch_size=50)
+
+            mock_get.assert_called_once_with(
+                "GET", f"{dlq.endpoint}/consume", params={"batch_size": 50}
+            )
+            assert result == []
+
+    def test_consume_returns_empty_list_on_204_no_content(self, dlq):
+        """Test DLQ consume returns empty list when API responds with 204 No Content."""
+        mock_response = mock_responses.create_mock_response_factory()(
+            status_code=204,
+            json_data=None,
+        )
+        with patch("httpx.Client.request", return_value=mock_response) as mock_get:
+            result = dlq.consume(batch_size=50)
+
+            mock_get.assert_called_once_with(
+                "GET", f"{dlq.endpoint}/consume", params={"batch_size": 50}
+            )
+            assert result == []
+
+    def test_consume_returns_empty_list_on_200_empty_body(self, dlq):
+        """Test DLQ consume returns empty list when API returns 200 with empty body."""
+        mock_response = mock_responses.create_mock_response_factory()(
+            status_code=200,
+            json_data=None,
+        )
+        mock_response.content = b""
+        with patch("httpx.Client.request", return_value=mock_response) as mock_get:
+            result = dlq.consume(batch_size=50)
+
+            mock_get.assert_called_once_with(
+                "GET", f"{dlq.endpoint}/consume", params={"batch_size": 50}
+            )
+            assert result == []
+
     @pytest.mark.parametrize(
         "scenario",
         [