list is not equivalent to typing.List under combination of generics and futures #6130
Description
Initial Checks
- I have searched GitHub for a duplicate issue and I'm sure this is something new
- I have searched Google & StackOverflow for a solution and couldn't find anything
- I have read and followed the docs and still think this is a bug
- I am confident that the issue is with pydantic (not my code, or another library in the ecosystem like FastAPI or mypy)
Description
This is a strange one - under the below conditions, exchanging typing.List for the more modern list produces the below error. I can't reproduce in a simpler example than this - it looks to me like a bug in pydantic:
Traceback (most recent call last):
File "pydantic/validators.py", line 751, in pydantic.validators.find_validators
TypeError: issubclass() arg 1 must be a class
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "{path_to_test}/test.py", line 11, in <module>
outer = Outer["Inner"]
File "{path_to_pydantic}/pydantic/generics.py", line 163, in __class_getitem__
_prepare_model_fields(created_model, fields, instance_type_hints, typevars_map)
File "{path_to_pydantic}/pydantic/generics.py", line 389, in _prepare_model_fields
field.prepare()
File "pydantic/fields.py", line 552, in pydantic.fields.ModelField.prepare
File "pydantic/fields.py", line 758, in pydantic.fields.ModelField._type_analysis
File "pydantic/fields.py", line 808, in pydantic.fields.ModelField._create_sub_type
File "pydantic/fields.py", line 436, in pydantic.fields.ModelField.__init__
File "pydantic/fields.py", line 557, in pydantic.fields.ModelField.prepare
File "pydantic/fields.py", line 831, in pydantic.fields.ModelField.populate_validators
File "pydantic/validators.py", line 760, in find_validators
RuntimeError: error checking inheritance of 'Inner' (type: str)
I've also displayed the minimal example below - thanks!
Example Code
from typing import Generic, List, TypeVar
from pydantic import BaseModel
from pydantic.generics import GenericModel
ChangingType = TypeVar("ChangingType")
class Outer(GenericModel, Generic[ChangingType]):
fields_: list[ChangingType] # Swapping list -> List on this line fixes the bug
outer = Outer["Inner"]
class Inner(BaseModel):
new: list[outer]
outer.update_forward_refs()
Inner.update_forward_refs()
out = Inner.parse_obj({"new": [{"fields_": []}]})
print(out)Python, Pydantic & OS Version
pydantic version: 1.10.9
pydantic compiled: True
install path: /{package location}/.venv/lib64/python3.10/site-packages/pydantic
python version: 3.10.10 (main, Feb 8 2023, 00:00:00) [GCC 12.2.1 20221121 (Red Hat 12.2.1-4)]
platform: Linux-5.10.16.3-microsoft-standard-WSL2-x86_64-with-glibc2.35
optional deps. installed: ['typing-extensions']
Affected Components
- Compatibility between releases
- Data validation/parsing
- Data serialization -
.dict()and.json() - JSON Schema
- Dataclasses
- Model Config
- Field Types - adding or changing a particular data type
- Function validation decorator
- Generic Models
- Other Model behaviour -
construct(), pickling, private attributes, ORM mode - Plugins and integration with other tools - mypy, FastAPI, python-devtools, Hypothesis, VS Code, PyCharm, etc.