test_error_to_success_conversion() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_composition.py lines 212–241

    def test_error_to_success_conversion(self) -> None:
        """Test handler converting error to success response."""

        def outer_error_handler(
            request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
        ) -> ModelResponse | AIMessage:
            try:
                return handler(request)
            except Exception:
                # Middleware can return AIMessage - it will be normalized to ModelResponse
                return AIMessage(content="Fallback response")

        def inner_passthrough(
            request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
        ) -> ModelResponse:
            return handler(request)

        composed = _chain_model_call_handlers([outer_error_handler, inner_passthrough])
        assert composed is not None

        def mock_base_handler(req: ModelRequest) -> ModelResponse:
            msg = "Model failed"
            raise ValueError(msg)

        result = composed(create_test_request(), mock_base_handler)

        # AIMessage was automatically normalized into ExtendedModelResponse
        assert isinstance(result, _ComposedExtendedModelResponse)
        assert result.model_response.result[0].content == "Fallback response"
        assert result.model_response.structured_response is None