Fix Gemini API content filter handling (#746)

## Summary - avoid AttributeError when Gemini API returns `None` for chat message - return empty output if message is filtered - add regression test ## Testing - `make format` - `make lint` - `make mypy` - `make tests` Towards #744

Author: rm-openai

src/agents/models/openai_chatcompletions.py

@@ -71,12 +71,22 @@ async def get_response(
  stream=False,
  )
 
+ first_choice = response.choices[0]
+ message = first_choice.message
+
  if _debug.DONT_LOG_MODEL_DATA:
  logger.debug("Received model response")
  else:
- logger.debug(
- f"LLM resp:\n{json.dumps(response.choices[0].message.model_dump(), indent=2)}\n"
- )
+ if message is not None:
+ logger.debug(
+ "LLM resp:\n%s\n",
+ json.dumps(message.model_dump(), indent=2),
+ )
+ else:
+ logger.debug(
+ "LLM resp had no message. finish_reason: %s",
+ first_choice.finish_reason,
+ )
 
  usage = (
  Usage(
@@ -101,13 +111,15 @@ async def get_response(
  else Usage()
  )
  if tracing.include_data():
- span_generation.span_data.output = [response.choices[0].message.model_dump()]
+ span_generation.span_data.output = (
+ [message.model_dump()] if message is not None else []
+ )
  span_generation.span_data.usage = {
  "input_tokens": usage.input_tokens,
  "output_tokens": usage.output_tokens,
  }
 
- items = Converter.message_to_output_items(response.choices[0].message)
+ items = Converter.message_to_output_items(message) if message is not None else []
 
  return ModelResponse(
  output=items,

tests/test_openai_chatcompletions.py

@@ -191,6 +191,40 @@ async def patched_fetch_response(self, *args, **kwargs):
  assert fn_call_item.arguments == "{'x':1}"
 
 
+@pytest.mark.allow_call_model_methods
+@pytest.mark.asyncio
+async def test_get_response_with_no_message(monkeypatch) -> None:
+ """If the model returns no message, get_response should return an empty output."""
+ msg = ChatCompletionMessage(role="assistant", content="ignored")
+ choice = Choice(index=0, finish_reason="content_filter", message=msg)
+ choice.message = None # type: ignore[assignment]
+ chat = ChatCompletion(
+ id="resp-id",
+ created=0,
+ model="fake",
+ object="chat.completion",
+ choices=[choice],
+ usage=None,
+ )
+
+ async def patched_fetch_response(self, *args, **kwargs):
+ return chat
+
+ monkeypatch.setattr(OpenAIChatCompletionsModel, "_fetch_response", patched_fetch_response)
+ model = OpenAIProvider(use_responses=False).get_model("gpt-4")
+ resp: ModelResponse = await model.get_response(
+ system_instructions=None,
+ input="",
+ model_settings=ModelSettings(),
+ tools=[],
+ output_schema=None,
+ handoffs=[],
+ tracing=ModelTracing.DISABLED,
+ previous_response_id=None,
+ )
+ assert resp.output == []
+
+
 @pytest.mark.asyncio
 async def test_fetch_response_non_stream(monkeypatch) -> None:
  """