Bug: Unsupported type: ForwardRef on field for pydantic ModelFactory

[mshonichev]

Description

Seems like Polyfactory don't respect forward type annotations when generating factories for Pydantic models.

When Pydantic model references another model and the latter is not yet defined, it is advised to either explicitly put type annotation in quotes to annotate type in forward or use implicit automatic forward annotations by doing from __future__ import annotations.

For such models, Polyfactory fails to create proper working ModelFactory which raises exceptions upon model build.

URL to code causing the issue

No response

MCVE

from __future__ import annotations

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


class Resp(BaseModel):
    name: str | None = Field(default=None, examples=["response"])
    coll: Coll | None


class Item(BaseModel):
    name: str = Field(..., examples=["item"])
    field: str | None = None


class Coll(BaseModel):
    items: list[Item] | None = None


# Resp.model_rebuild()


class RespFactory(ModelFactory[Resp]):
    ...


def test_inc() -> None:
    resp = RespFactory.build(name="9287")
    print(resp)

Steps to reproduce

1. Run example

Expected: No errors, model built

Actual: 

E       polyfactory.exceptions.ParameterException: Unsupported type: ForwardRef('Coll | None') on field 'coll' from class RespFactory.
E       
E       Either use 'add_provider', extend the providers map, or add a factory function for the field on the model.

(partial) workaround:
Sometimes <Model>.model_rebuild() helps fix forward annotations.

Sometimes if one to remove from __future__ import annotations and reorder model classes definitions so that no forward annotations occur, then ModelFactory works as expected.

However, this is not always the case, due to e.g. legacy imported code or circular referencing data structures.

Screenshots

"In the format of: ![SCREENSHOT_DESCRIPTION](SCREENSHOT_LINK.png)"

Logs

Release Version

2.20.0

Platform

• Linux
• Mac
• Windows
• Other (Please specify in the description above)

[adhtruong]

PRs welcome to fix. I think for main use case here can call BaseModel.model_rebuild - either in your base class or in ModelFactory.__init_subclass__.

Probably out of scope to support all models for unbuilt schema and try resolve references in general and try delegate this to exposed pydantic api if possible