Mypy plugin crashes when encountering from_orm method on user's classes

[ThirVondukr]

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

I have a OrmMixin (provided in example code) to help with mapping sqlalchemy models into strawberry-graphql models.

Mypy plugin seems to have problems with from_orm method and works fine if it's renamed, for example into from_orm_.

$ mypy main.py
main.py:19: error: The pydantic mypy plugin ran into unexpected behavior: ctx.type: Type[main.OrmMixin[_TModel`1, _TType`2]] (of type TypeType)
Please consider reporting this bug at https://github.com/pydantic/pydantic/issues/new/choose so we can try to fix it!  [pydantic-unexpected]       
main.py:23: error: The pydantic mypy plugin ran into unexpected behavior: ctx.type: Type[main.OrmMixin[_TModel`1, _TType`2]] (of type TypeType)
Please consider reporting this bug at https://github.com/pydantic/pydantic/issues/new/choose so we can try to fix it!  [pydantic-unexpected]       
Found 2 errors in 1 file (checked 1 source file)

Example Code

import abc
from collections.abc import Iterable
from typing import Generic, TypeVar

_TModel = TypeVar("_TModel")
_TType = TypeVar("_TType")


class OrmMixin(Generic[_TModel, _TType]):
    @classmethod
    @abc.abstractmethod
    def from_orm(cls, model: _TModel) -> _TType:
        raise NotImplementedError

    @classmethod
    def from_orm_optional(cls, model: _TModel | None) -> _TType | None:
        if model is None:
            return None
        return cls.from_orm(model)

    @classmethod
    def from_orm_list(cls, models: Iterable[_TModel]) -> list[_TType]:
        return [cls.from_orm(model) for model in models]

Python, Pydantic & OS Version

pydantic version: 1.10.6
pydantic compiled: True
install path: .venv\Lib\site-packages\pydantic
python version: 3.11.1 (tags/v3.11.1:a7a450f, Dec  6 2022, 19:58:39) [MSC v.1934 64 bit (AMD64)]
platform: Windows-10-10.0.19044-SP0
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.

[jtc42]

I'm having to just # type: ignore these lines for now, which seems to stop the crash at least. Thanks for reporting!

[dmontagu]

Can you share some code showing how you are using it to produce this error?

[dmontagu]

I don't get this error running mypy over the code in the snippet you've shared; however, I looked into it a bit and I see where it needs handling, and I think I it should be straightforward to fix if you can give me some code that shows how to reproduce the issue.

[dmontagu]

Oh also — could you share what version of mypy you are using? (You can find this by running mypy --version)

[ThirVondukr]

$ mypy --version
mypy 1.1.1 (compiled: yes)

It errors out on provided code:

import abc
from collections.abc import Iterable
from typing import Generic, TypeVar

_TModel = TypeVar("_TModel")
_TType = TypeVar("_TType")


class OrmMixin(Generic[_TModel, _TType]):
    @classmethod
    @abc.abstractmethod
    def from_orm(cls, model: _TModel) -> _TType:
        raise NotImplementedError

    @classmethod
    def from_orm_optional(cls, model: _TModel | None) -> _TType | None:
        if model is None:
            return None
        return cls.from_orm(model)

    @classmethod
    def from_orm_list(cls, models: Iterable[_TModel]) -> list[_TType]:
        return [cls.from_orm(model) for model in models]

Mypy config:

[tool.mypy]
python_version = "3.11"
plugins = [
    "pydantic.mypy",
]

check_untyped_defs = true
disallow_untyped_calls = true
disallow_untyped_defs = true
disallow_incomplete_defs = true
disallow_any_generics = true
no_implicit_optional = true

warn_redundant_casts = true
warn_unused_ignores = true
warn_return_any = true
warn_unreachable = true

strict_optional = true
strict_equality = true

[ThirVondukr]

# pyproject.toml
dependencies = [
    "mypy>=1.1.1",
    "pydantic>=1.10.6",
]

$ pip freeze
mypy==1.1.1
mypy-extensions==1.0.0
pydantic==1.10.6
typing_extensions==4.5.0

[samuelcolvin]

see #5192

[ThirVondukr]

Same behavior with 1.0.1

[dmontagu]

@ThirVondukr thank you for your help/patience. This turned out to have an easy fix so I was able to get it in. That said, I think some of the other issues listed in #5192 will be more involved to resolve, so I don't want to promise as quick of a turn-around on those.

[ThirVondukr]

Don't stress it, thanks for your help 😃

[dmontagu]

Closed by #5193 and #5194