django-stubs/README.md

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# pep484 stubs for Django

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This package contains [type stubs](https://www.python.org/dev/peps/pep-0561/) 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

```bash
pip install django-stubs[compatible-mypy]
```

To make mypy aware of the plugin, you need to add

```ini
[mypy]
plugins =
    mypy_django_plugin.main

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

in your `mypy.ini` or `setup.cfg` [file](https://mypy.readthedocs.io/en/latest/config_file.html).

[pyproject.toml](https://mypy.readthedocs.io/en/stable/config_file.html#using-a-pyproject-toml-file) configurations are also supported:

```toml
[tool.mypy]
plugins = ["mypy_django_plugin.main"]

[tool.django-stubs]
django_settings_module = "myproject.settings"
```

Two things happening here:

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

This fully working [typed boilerplate](https://github.com/wemake-services/wemake-django-template) can serve you as an example.

## Version compatibility

We rely on different `django` and `mypy` versions:

| django-stubs | mypy version | django version | python version
|--------------| ---- | ---- | ---- |
| 1.12.0       | 0.931+ | 3.2.x or 4.0.x | ^3.7
| 1.11.0       | 0.931+ | 3.2.x | ^3.7
| 1.10.0       | 0.931+ | 3.2.x | ^3.7
| 1.9.0        | 0.910 | 3.2.x | ^3.6
| 1.8.0        | 0.812 | 3.1.x | ^3.6
| 1.7.0        | 0.790 | 2.2.x \|\| 3.x | ^3.6
| 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 independent from Django at the moment.
There's a [proposal](https://github.com/django/deps/pull/65) to merge our project into the Django itself.
You can show your support by liking 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

The current implementation uses Django's runtime to extract information about models, so it might crash if your installed apps or `models.py` are broken.

In other words, if your `manage.py runserver` crashes, mypy will crash too.
You can also run `mypy` with [`--tb`](https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-show-traceback)
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]`, `Manager[MyModel]` or some other Django-based Generic types.

This happens because these Django classes do not support [`__class_getitem__`](https://www.python.org/dev/peps/pep-0560/#class-getitem) magic method in runtime.

1. You can go with our [`django_stubs_ext`](https://github.com/typeddjango/django-stubs/tree/master/django_stubs_ext) helper, that patches all the types we use as Generic in django.

   Install it:

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

   And then place in your top-level settings:

   ```python
   import django_stubs_ext

   django_stubs_ext.monkeypatch()
   ```

   Note: This monkey patching approach will only work when using Python 3.7 and higher, when the `__class_getitem__` magic method was introduced.

   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 `mypy` and as a regular `str` in runtime.

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

Django's built in [`HttpRequest`](https://docs.djangoproject.com/en/4.0/ref/request-response/#django.http.HttpRequest) has the attribute `user` that resolves to the type

```python
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:

```python
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.


### My QuerySet methods are returning Any rather than my Model

If you are using `MyQuerySet.as_manager()`:

Example:

```python
from django.db import models

class MyModelQuerySet(models.QuerySet):
    pass


class MyModel(models.Model):
    bar = models.IntegerField()
    objects = MyModelQuerySet.as_manager()


def use_my_model() -> int:
    foo = MyModel.objects.get(id=1) # Should now be `MyModel`
    return foo.xyz # Gives an error
```

Or if you're using `Manager.from_queryset`:

Example:

```python
from django.db import models


class MyModelQuerySet(models.QuerySet):
    pass


MyModelManager = models.Manager.from_queryset(MyModelQuerySet)


class MyModel(models.Model):
    bar = models.IntegerField()
    objects = MyModelManager()


def use_my_model() -> int:
    foo = MyModel.objects.get(id=1) # Should now be `MyModel`
    return foo.xyz # Gives an error
```

### Why am I getting incompatible return type errors on my custom managers?

If you declare your custom managers without generics and override built-in
methods you might see an error message about incompatible error messages,
something like this:

```python
from django.db import models

class MyManager(model.Manager):
    def create(self, **kwargs) -> "MyModel":
        pass
```

will cause this error message:

```
error: Return type "MyModel" of "create" incompatible with return type "_T" in supertype "BaseManager"
```

This is happening because the `Manager` class is generic, but without
specifying generics the built-in manager methods are expected to return the
generic type of the base manager, which is any model. To fix this issue you
should declare your manager with your model as the type variable:

```python
class MyManager(models.Manager["MyModel"]):
    ...
```

### How do I annotate cases where I called QuerySet.annotate?

Django-stubs provides a special type, `django_stubs_ext.WithAnnotations[Model]`, which indicates that the `Model` has
been annotated, meaning it allows getting/setting extra attributes on the model instance.

Optionally, you can provide a `TypedDict` of these attributes,
e.g. `WithAnnotations[MyModel, MyTypedDict]`, to specify which annotated attributes are present.

Currently, the mypy plugin can recognize that specific names were passed to `QuerySet.annotate` and
include them in the type, but does not record the types of these attributes.

The knowledge of the specific annotated fields is not yet used in creating more specific types for `QuerySet`'s
`values`, `values_list`, or `filter` methods, however knowledge that the model was annotated _is_ used to create a
broader type result type for `values`/`values_list`, and to allow `filter`ing on any field.

```python
from typing import TypedDict
from django_stubs_ext import WithAnnotations
from django.db import models
from django.db.models.expressions import Value


class MyModel(models.Model):
    username = models.CharField(max_length=100)


def func(m: WithAnnotations[MyModel]) -> str:
    return m.asdf  # OK, since the model is annotated as allowing any attribute


func(MyModel.objects.annotate(foo=Value("")).get(id=1))  # OK
func(
    MyModel.objects.get(id=1)
)  # Error, since this model will not allow access to any attribute


class MyTypedDict(TypedDict):
    foo: str


def func2(m: WithAnnotations[MyModel, MyTypedDict]) -> str:
    print(m.bar)  # Error, since field "bar" is not in MyModel or MyTypedDict.
    return m.foo  # OK, since we said field "foo" was allowed


func(MyModel.objects.annotate(foo=Value("")).get(id=1))  # OK
func(MyModel.objects.annotate(bar=Value("")).get(id=1))  # Error
```

## Related projects

- [`awesome-python-typing`](https://github.com/typeddjango/awesome-python-typing) - Awesome list of all typing-related things in Python.
- [`djangorestframework-stubs`](https://github.com/typeddjango/djangorestframework-stubs) - Stubs for Django REST Framework.
- [`pytest-mypy-plugins`](https://github.com/typeddjango/pytest-mypy-plugins) - `pytest` plugin that we use for testing `mypy` stubs and plugins.
- [`wemake-django-template`](https://github.com/wemake-services/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.

## Contributing

This project is open source and community driven. As such we encourage contributions big and small. You can contribute by doing any of the following:

1. Contribute code (e.g. improve stubs, add plugin capabilities, write tests etc) - to do so please follow the [contribution guide](./CONTRIBUTING.md).
2. Assist in code reviews and discussions in issues.
3. Identify bugs and issues and report these
4. Ask and answer questions on [StackOverflow](https://stackoverflow.com/questions/tagged/django-stubs)

You can always also reach out in gitter to discuss your contributions!