ignore empty text parts (#466)

Author: samuelcolvin

pydantic_ai_slim/pydantic_ai/agent.py

@@ -841,11 +841,13 @@ async def _handle_model_response(
         """
         texts: list[str] = []
         tool_calls: list[_messages.ToolCallPart] = []
-        for item in model_response.parts:
-            if isinstance(item, _messages.TextPart):
-                texts.append(item.content)
+        for part in model_response.parts:
+            if isinstance(part, _messages.TextPart):
+                # ignore empty content for text parts, see #437
+                if part.content:
+                    texts.append(part.content)
             else:
-                tool_calls.append(item)
+                tool_calls.append(part)
 
         if texts:
             text = '\n\n'.join(texts)

tests/test_agent.py

@@ -1112,3 +1112,15 @@ def return_settings(_: list[ModelMessage], info: AgentInfo) -> ModelResponse:
     my_agent = Agent(FunctionModel(return_settings), model_settings={'temperature': 0.1})
     assert (await my_agent.run('Hello')).data == IsJson({'temperature': 0.1})
     assert (await my_agent.run('Hello', model_settings={'temperature': 0.5})).data == IsJson({'temperature': 0.5})
+
+
+async def test_empty_text_part():
+    def return_empty_text(_: list[ModelMessage], info: AgentInfo) -> ModelResponse:
+        assert info.result_tools is not None
+        args_json = '{"response": ["foo", "bar"]}'
+        return ModelResponse(parts=[TextPart(''), ToolCallPart.from_json(info.result_tools[0].name, args_json)])
+
+    agent = Agent(FunctionModel(return_empty_text), result_type=tuple[str, str])
+
+    result = await agent.run('Hello')
+    assert result.data == ('foo', 'bar')