Pydantic str type coercion from numeric types

[fahminlb33]

Hello, I faced this simple error today about type coercion. The error is raised when an int are passed into str type in signature. Below is my signature class.

class LaptopSpecification(dspy.Signature):
    """Extracts laptop technical specification."""

    description: str = dspy.InputField()

    brand: Optional[str] = dspy.OutputField()
    series_model: Optional[str] = dspy.OutputField()
    processor: Optional[str] = dspy.OutputField()
    memory: Optional[str] = dspy.OutputField()
    storage: Optional[str] = dspy.OutputField()
    graphics_card: Optional[str] = dspy.OutputField()

Below is the result from dspy.inspect_history()

{
    "reasoning": "The laptop is suitable for general use and office work due to its Intel Core i5 processor, 16GB of RAM, and 512GB SSD storage.",
    "brand": "HP",
    "series_model": "14",
    "processor": "Intel Core i5-1235U (up to 4.4 GHz with Intel Turbo Boost Technology)",
    "memory": "16GB DDR4-3200 MHz RAM",
    "storage": "512GB PCIe NVMe M.2 SSD",
    "graphics_card": "Intel Iris Xe Graphics"
}

I guess the problem is this: because the series_model is just the string 14, the adapter incorrectly parsed it into an int and then the error is raised in this line:

dspy/dspy/adapters/json_adapter.py

Line 139 in 526bc19

return TypeAdapter(annotation).validate_python(parsed_value)

For Pydantic models, we can do coerce_numbers_to_str=True to solve this type coercion problem, but currently I can't find any documentation in DSPy that allows me to set the model_config of a signature nor the DSPy respect the model_config in the signature class.

model_config = ConfigDict(coerce_numbers_to_str=True)

For now, this is my hack to solve this number coercion problem.

return TypeAdapter(annotation, config=ConfigDict(coerce_numbers_to_str=True)).validate_python(parsed_value)

Is there a plan to allow signature class to accept a ConfigDict or specify it somewhere to control this behavior?

Thanks

Edit:
Python: 3.11
Package manager: uv 0.5.9
DSPy: 2.5.43

[okhat]

Hey @fahminlb33 ! Thanks a lot for opening this. It looks like a bug to me, but I should check deeper.

I don't think the best fix is via coerce_numbers_to_str. We may need to change the order in which parsing happens.

[fahminlb33]

I agree, the issue might lie somewhere else, and passing a custom ConfigDict is a temporary fix in this case.

I think it would be beneficial to also expose a way to set a custom ConfigDict for a signature. It would offer more control of the signature parsing behavior.