fix empty user message error (#15784)

Author: Sameerlite

litellm/llms/vertex_ai/common_utils.py

@@ -239,12 +239,12 @@ def _check_text_in_content(parts: List[PartType]) -> bool:
     """
     check that user_content has 'text' parameter.
         - Known Vertex Error: Unable to submit request because it must have a text parameter.
-        - 'text' param needs to be len > 0
+        - 'text' param needs to be present (empty strings are valid)
         - Relevant Issue: https://github.com/BerriAI/litellm/issues/5515
     """
     has_text_param = False
     for part in parts:
-        if "text" in part and part.get("text"):
+        if "text" in part and part.get("text") is not None:
             has_text_param = True
 
     return has_text_param

litellm/llms/vertex_ai/gemini/transformation.py

@@ -263,7 +263,6 @@ def _gemini_convert_messages_with_history(  # noqa: PLR0915
                 elif (
                     _message_content is not None
                     and isinstance(_message_content, str)
-                    and len(_message_content) > 0
                 ):
                     _part = PartType(text=_message_content)
                     user_content.append(_part)
@@ -335,9 +334,8 @@ def _gemini_convert_messages_with_history(  # noqa: PLR0915
                 elif (
                     _message_content is not None
                     and isinstance(_message_content, str)
-                    and _message_content
                 ):
-                    assistant_text = _message_content  # either string or none
+                    assistant_text = _message_content
                     assistant_content.append(PartType(text=assistant_text))  # type: ignore
 
                 ## HANDLE ASSISTANT FUNCTION CALL

tests/test_litellm/llms/vertex_ai/gemini/test_vertex_ai_gemini_transformation.py

@@ -1,6 +1,7 @@
 from litellm.llms.vertex_ai.gemini.transformation import (
     check_if_part_exists_in_parts,
     _transform_request_body,
+    _gemini_convert_messages_with_history,
 )
 
 
@@ -155,3 +156,23 @@ def test_metadata_to_labels_vertex_only():
     )
     assert "labels" in result
     assert result["labels"] == {"user": "john_doe", "project": "test-project"}
+
+
+def test_empty_content_handling():
+    """Test that empty content strings are properly handled in Gemini message transformation"""
+    # Test with empty content in user message
+    messages = [
+        {
+            "content": "",
+            "role": "user"
+        }
+    ]
+    
+    contents = _gemini_convert_messages_with_history(messages=messages)
+    
+    # Verify that the content was properly transformed
+    assert len(contents) == 1
+    assert contents[0]["role"] == "user"
+    assert len(contents[0]["parts"]) == 1
+    assert "text" in contents[0]["parts"][0]
+    assert contents[0]["parts"][0]["text"] == ""