Typesafe Django Framework

This package contains type stubs and a custom mypy plugin to provide more precise static types and type inference for Django framework. Django uses some Python "magic" that makes having precise types for some code patterns problematic. This is why we need this project. The final goal is to be able to get precise types for most common patterns.

Installation

pip install django-stubs

See Configuration section to get started.

Configuration

To make mypy happy, you will need to add:

[mypy]
plugins =
    mypy_django_plugin.main
    
[mypy.plugins.django-stubs]
django_settings_module = "myproject.settings"

in your mypy.ini or setup.cfg file.

Two things happeining here:

We need to explicitly list our plugin to be loaded by mypy
Our plugin also requires django settings module (what you put into DJANGO_SETTINGS_MODULE variable) to be specified

This fully working typed boilerplate can serve you as an example.

Version compatibility

We rely on different django and mypy versions:

django-stubs	mypy version	django version	python version
1.6.0	0.780	2.2.x \|\| 3.x	^3.6
1.5.0	0.770	2.2.x \|\| 3.x	^3.6
1.4.0	0.760	2.2.x \|\| 3.x	^3.6
1.3.0	0.750	2.2.x \|\| 3.x	^3.6
1.2.0	0.730	2.2.x	^3.6
1.1.0	0.720	2.2.x	^3.6
0.12.x	old semantic analyzer (<0.711), dmypy support	2.1.x	^3.6

FAQ

Is this an official Django project?

No, it is not. We are indendepent from Django at the moment. There's a proposal to merge our project into the Django itself. You show your support by linking the PR.

Is it safe to use this in production?

Yes, it is! This project does not affect your runtime at all. It only affects mypy type checking process.

But, it does not make any sense to use this project without mypy.

mypy crashes when I run it with this plugin installed

Current implementation uses Django runtime to extract models information, so it will crash, if your installed apps or models.py is not correct. For this same reason, you cannot use reveal_type inside global scope of any Python file that will be executed for django.setup().

In other words, if your manage.py runserver crashes, mypy will crash too. You can also run mypy with --tb option to get extra information about the error.

I cannot use QuerySet or Manager with type annotations

You can get a TypeError: 'type' object is not subscriptable when you will try to use QuerySet[MyModel] or Manager[MyModel].

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

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

Currently we are working on providing __class_getitem__ to the classes where we need them.

How can I create a HttpRequest that's guaranteed to have an authenticated user?

Django's built in HttpRequest has the attribute user that resolves to the type

Union[User, AnonymousUser]

where User is the user model specified by the AUTH_USER_MODEL setting.

If you want a HttpRequest that you can type-annotate with where you know that the user is authenticated you can subclass the normal HttpRequest class like so:

from django.http import HttpRequest
from my_user_app.models import MyUser

class AuthenticatedHttpRequest(HttpRequest):
    user: MyUser

And then use AuthenticatedHttpRequest instead of the standard HttpRequest for when you know that the user is authenticated. For example in views using the @login_required decorator.

Related projects

awesome-python-typing - Awesome list of all typing-related things in Python.
djangorestframework-stubs - Stubs for Django REST Framework.
pytest-mypy-plugins - pytest plugin that we use for testing mypy stubs and plugins.
wemake-django-template - Create new typed Django projects in seconds.

To get help

We have Gitter here: https://gitter.im/mypy-django/Lobby

If you think you have more generic typing issue, please refer to https://github.com/python/mypy and their Gitter.

vgel/django-stubs