django-types

django-types

Type stubs for Django.

Note: this project was forked from https://github.com/typeddjango/django-stubs with the goal of removing the mypy plugin dependency so that mypy can't crash due to Django config, and that non-mypy type checkers like pyright will work better with Django.

install

pip install django-types

You can get a TypeError: 'type' object is not subscriptable when you will try to use QuerySet[MyModel], Manager[MyModel] or some other Django-based Generic types.

This happens because these Django classes do not support __class_getitem__ magic method in runtime.

1. You can go with django_stubs_ext helper, that patches all the types we use as Generic in django.

   Install it:

   pip install django-stubs-ext  # as a production dependency
   

   And then place in your top-level settings:

   import django_stubs_ext
   
   django_stubs_ext.monkeypatch()
   

   You can add extra types to patch with django_stubs_ext.monkeypatch(extra_classes=[YourDesiredType])

2. You can use strings instead: 'QuerySet[MyModel]' and 'Manager[MyModel]', this way it will work as a type for type-checking and as a regular str in runtime.

usage

ForeignKey ids and related names as properties in ORM models

When defining a Django ORM model with a foreign key, like so:

class User(models.Model):
    team = models.ForeignKey(
        "Team",
        null=True,
        on_delete=models.SET_NULL,
    )
    role = models.ForeignKey(
        "Role",
        null=True,
        on_delete=models.SET_NULL,
        related_name="users",
    )

two properties are created, team as expected, and team_id. Also, a related manager called user_set is created on Team for the reverse access.

In order to properly add typing to the foreign key itself and also for the created ids you can do something like this:

from typing import TYPE_CHECKING

from someapp.models import Team
if TYPE_CHECKING:
    # In this example Role cannot be imported due to circular import issues,
    # but doing so inside TYPE_CHECKING will make sure that the typing below
    # knows what "Role" means
    from anotherapp.models import Role


class User(models.Model):
    team_id: Optional[int]
    team = models.ForeignKey(
        Team,
        null=True,
        on_delete=models.SET_NULL,
    )
    role_id: int
    role = models.ForeignKey["Role"](
        "Role",
        null=False,
        on_delete=models.SET_NULL,
        related_name="users",
    )


reveal_type(User().team)
# note: Revealed type is 'Optional[Team]'
reveal_type(User().role)
# note: Revealed type is 'Role'

This will make sure that team_id and role_id can be accessed. Also, team and role will be typed to their right objects.

To be able to access the related manager Team and Role you could do:

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    # This doesn't really exists on django so it always need to be imported this way
    from django.db.models.manager import RelatedManager
    from user.models import User


class Team(models.Model):
    if TYPE_CHECKING:
        user_set = RelatedManager["User"]()


class Role(models.Model):
    if TYPE_CHECKING:
        users = RelatedManager["User"]()

reveal_type(Team().user_set)
# note: Revealed type is 'RelatedManager[User]'
reveal_type(Role().users)
# note: Revealed type is 'RelatedManager[User]'

An alternative is using annotations:

from __future__ import annotations  # or just be in python 3.11

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from django.db.models import Manager
    from user.models import User


class Team(models.Model):
    user_set: Manager[User]


class Role(models.Model):
    users: Manager[User]

reveal_type(Team().user_set)
# note: Revealed type is 'Manager[User]'
reveal_type(Role().users)
# note: Revealed type is 'Manager[User]'

id Field

By default Django will create an AutoField for you if one doesn't exist.

For type checkers to know about the id field you'll need to declare the field explicitly.

# before
class Post(models.Model):
    ...

# after
class Post(models.Model):
    id = models.AutoField(primary_key=True)
    # OR
    id: int

HttpRequest's user property

The HttpRequest's user property has a type of Union[AbstractBaseUser, AnonymousUser], but for most of your views you'll probably want either an authed user or an AnonymousUser.

So we can define a subclass for each case:

class AuthedHttpRequest(HttpRequest):
    user: User  # type: ignore [assignment]

And then you can use it in your views:

@auth.login_required
def activity(request: AuthedHttpRequest, team_id: str) -> HttpResponse:
    ...

You can also get more strict with your login_required decorator so that the first argument of the function it is decorating is AuthedHttpRequest:

from typing import Any, Union, TypeVar, cast
from django.http import HttpRequest, HttpResponse
from typing_extensions import Protocol
from functools import wraps

class RequestHandler1(Protocol):
    def __call__(self, request: AuthedHttpRequest) -> HttpResponse:
        ...


class RequestHandler2(Protocol):
    def __call__(self, request: AuthedHttpRequest, __arg1: Any) -> HttpResponse:
        ...


RequestHandler = Union[RequestHandler1, RequestHandler2]


# Verbose bound arg due to limitations of Python typing.
# see: https://github.com/python/mypy/issues/5876
_F = TypeVar("_F", bound=RequestHandler)


def login_required(view_func: _F) -> _F:
    @wraps(view_func)
    def wrapped_view(
        request: AuthedHttpRequest, *args: object, **kwargs: object
    ) -> HttpResponse:
        if request.user.is_authenticated:
            return view_func(request, *args, **kwargs)  # type: ignore [call-arg]
        raise AuthenticationRequired

    return cast(_F, wrapped_view)

Then the following will type error:

@auth.login_required
def activity(request: HttpRequest, team_id: str) -> HttpResponse:
    ...

related

• https://github.com/sbdchd/djangorestframework-types
• https://github.com/sbdchd/celery-types
• https://github.com/sbdchd/mongo-types
• https://github.com/sbdchd/msgpack-types