test_fetch_last_ai_and_tool_messages_no_ai_message() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/test_fetch_last_ai_and_tool_messages.py lines 48–65

def test_fetch_last_ai_and_tool_messages_no_ai_message() -> None:
    """Test handling when no AIMessage exists in messages.

    This is the edge case that caused issue #34792 - UnboundLocalError
    when using RemoveMessage(id=REMOVE_ALL_MESSAGES) to clear thread messages.
    The function now returns None for the AIMessage, allowing callers to
    handle this edge case explicitly.
    """
    messages = [
        HumanMessage(content="Hello"),
        SystemMessage(content="You are a helpful assistant"),
    ]

    ai_msg, tool_msgs = _fetch_last_ai_and_tool_messages(messages)

    # Should return None when no AIMessage is found
    assert ai_msg is None
    assert len(tool_msgs) == 0