Bug: Incorrect generation on literal values

[scott-boost]

Description

When a pydantic model has a field that is a union of literals, the factory doesn't generate correct values

URL to code causing the issue

No response

MCVE

from typing import Literal

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

type MyFieldType = Literal["a"] | Literal["b"]

class MyModel(BaseModel):
    my_field: MyFieldType


class MyModelFactory(ModelFactory[MyModel]):
    pass

MyModelFactory.build()

Steps to reproduce

run the MCVE

Screenshots

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

Logs

venv/bin/python my_file.py 
venv/lib/python3.14/site-packages/polyfactory/factories/pydantic_factory.py:86: UserWarning: Core Pydantic V1 functionality isn't compatible with Python 3.14 or greater.
  import pydantic.v1 as pydantic_v1  # type: ignore[no-redef]
Traceback (most recent call last):
  File "my_file.py", line 15, in <module>
    MyModelFactory.build()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "venv/lib/python3.14/site-packages/polyfactory/factories/pydantic_factory.py", line 548, in build
    return cls._create_model(kwargs["_build_context"], **processed_kwargs)
           ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "venv/lib/python3.14/site-packages/polyfactory/factories/pydantic_factory.py", line 577, in _create_model
    return cls.__model__(**kwargs)
           ~~~~~~~~~~~~~^^^^^^^^^^
  File "venv/lib/python3.14/site-packages/pydantic/main.py", line 250, in __init__
    validated_self = self.__pydantic_validator__.validate_python(data, self_instance=self)
pydantic_core._pydantic_core.ValidationError: 2 validation errors for MyModel
my_field.literal['a']
  Input should be 'a' [type=literal_error, input_value=typing.Literal['a'], input_type=_LiteralGenericAlias]
    For further information visit https://errors.pydantic.dev/2.12/v/literal_error
my_field.literal['b']
  Input should be 'b' [type=literal_error, input_value=typing.Literal['a'], input_type=_LiteralGenericAlias]
    For further information visit https://errors.pydantic.dev/2.12/v/literal_error

Release Version

3.0.0

Platform

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

[adhtruong]

Thanks for reporting.

This seems like a 3.14 specific bug due to https://docs.python.org/3/whatsnew/3.14.html#typing and handling of union representation. polyfactory doesn't support 3.14 officially yet so may run into edge cases like this but looking to support soon