Polyfactory and typing

[guillaume-alliander]

I am trying to have proper typing with polyfactory (python 3.12, pydantic 2, pyright)

from typing import Callable, Self, Type

from polyfactory.factories.pydantic_factory import ModelFactory
from pydantic import BaseModel

class Parent(BaseModel):
    @classmethod
    def generate_test_instance[T: BaseModel, **P](cls: Type[Callable[P, T]], *_: P.args, **kwargs: P.kwargs) -> T:
        class Factorio(ModelFactory[Self]):
            __model__ = cls # type: ignore

        return Factorio.build(**kwargs)

class Child(Parent):
    param: str

Child.generate_test_instance()

This is mostly correct (I have autocompletion of the Child parameters) but:

• there is a type: ignore inside my Factorio class, Expected when looking at the signature, but I cannot find a better one. At runtime, this works perfectly.
• Child.generate_test_instance() complains that param is mandatory. It is according to the Child spec, but because polyfactory fills up the parameters, it is actually not mandatory. Is there a way to fix this, as in having auto completion, an error if giving a wrong param, but no error if no params are given? In short, the parameters should be seen as optional.

[guacs]

@guillaume-alliander I'm so sorry, but I had missed this in my notifications. I'm not sure if what you're trying to achieve is possible, but I'll have to look into a bit to be really sure.

However, using it in this way (as a classmethod), you'll see a performance hit if you're creating a lot of instances since each time a new factory would be created which in turn means the model has to be parsed repeatedly.

[guillaume-alliander]

Thanks @guacs , I had not thought about the factory in the class method. This does not matter too much for me (it is only inside unit tests), but that is a good point I will look into.

I am aware that what I am trying to do (typing Optional) sounds quite tricky, that's why I am asking the expert :) Thanks for looking!