I ran into a problem with mypy on the Meta classes of Django models. The mypy issue tracker redirected my to this place.

Do you have an answer for this question? https://github.com/python/mypy/issues/3855

I made some new stubs for django dispatch and some core features. I also added the __setattr__ and __getattr__ so that people can tack on attributes dynamically (which is apparently a common pattern).

WIP: I also want to update MultiValueDict, as the get methods are not correctly typed.

mypy-lang has moved to mypy now, so in order to install the latest mypy `pip install mypy is needed, not mypy-lang.

More details here:

• https://github.com/python/mypy/commit/339ba96d1c36894577db072a0f90656fea83a05a#diff-04c6e90faac2675aa89e2176d2eec7d8

Bug Report

when trying to run "mypy" on my company's existing codebase I'm getting an error as follows:

root@826a40544ab8:/app/wwau/wwau# mypy --config-file=./setup.cfg ./wwau/settings.py 
Error constructing plugin instance of NewSemanalDjangoPlugin

Traceback (most recent call last):
  File "/usr/local/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/usr/local/lib/python3.6/site-packages/mypy/__main__.py", line 8, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "mypy/main.py", line 90, in main
  File "mypy/build.py", line 180, in build
  File "mypy/build.py", line 229, in _build
  File "mypy/build.py", line 472, in load_plugins
  File "mypy/build.py", line 450, in load_plugins_from_config
  File "/usr/local/lib/python3.6/site-packages/mypy_django_plugin/main.py", line 100, in __init__
    self.django_context = DjangoContext(django_settings_module)
  File "/usr/local/lib/python3.6/site-packages/mypy_django_plugin/django/context.py", line 88, in __init__
    apps, settings = initialize_django(self.django_settings_module)
  File "/usr/local/lib/python3.6/site-packages/mypy_django_plugin/django/context.py", line 70, in initialize_django
    settings._setup()
  File "/usr/local/lib/python3.6/site-packages/django/conf/__init__.py", line 66, in _setup
    self._wrapped = Settings(settings_module)
  File "/usr/local/lib/python3.6/site-packages/django/conf/__init__.py", line 157, in __init__
    mod = importlib.import_module(self.SETTINGS_MODULE)
  File "/usr/local/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/app/wwau/wwau/wwau/settings.py", line 5, in <module>
    from common_settings import CommonBase, CommonLocal, CommonCI, CommonServer, VerboseLoggingMixin
  File "/app/shared/common_settings.py", line 17, in <module>
    class CommonBase(Configuration):
  File "/usr/local/lib/python3.6/site-packages/configurations/base.py", line 28, in __new__
    raise ImproperlyConfigured(install_failure)
django.core.exceptions.ImproperlyConfigured: django-configurations settings importer wasn't correctly installed. Please use one of the starter functions to install it as mentioned in the docs: https://django-configurations.readthedocs.io/

To Reproduce

Unable to reproduce in a similar django project sadly.

Expected Behavior

Just like in the other project - I'd like to see the mypy type errors in the console.

Actual Behavior

as above

Your Environment

• Mypy version used: mypy 0.790
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): [mypy] files=wwau,../../shared ignore_missing_imports=true plugins = mypy_django_plugin.main

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

• Python version used: Python 3.6.10
• Operating system and version: Linux 826a40544ab8 5.8.16-2-MANJARO #1 SMP PREEMPT Mon Oct 19 11:33:03 UTC 2020 x86_64 GNU/Linux

Encountered against the latest checkouts, with mypy==0.521

Two lines:

from django.views import View # type: ignore
from django.db import models  # type: ignore

Errors:

$ MYPYPATH=mypy-django mypy --strict-optional --disallow-untyped-calls test_mypy.py 
mypy-django/django/views/generic/list.pyi:3: error: No library stub file for module 'django.db.models'
mypy-django/django/views/generic/list.pyi:3: note: (Stub files are from https://github.com/python/typeshed)
mypy-django/django/views/generic/list.pyi:4: error: No library stub file for module 'django.db.models.query'

One line:

from django.views import View # type: ignore

Errors:

$ MYPYPATH=mypy-django mypy --strict-optional --disallow-untyped-calls test_mypy.py 
mypy-django/django/views/generic/dates.pyi:4: error: No library stub file for module 'django.db'
mypy-django/django/views/generic/dates.pyi:4: note: (Stub files are from https://github.com/python/typeshed)
mypy-django/django/views/generic/detail.pyi:3: error: No library stub file for module 'django.db'
mypy-django/django/views/generic/edit.pyi:3: error: No library stub file for module 'django.db'
mypy-django/django/views/generic/list.pyi:3: error: No library stub file for module 'django.db.models'
mypy-django/django/views/generic/list.pyi:4: error: No library stub file for module 'django.db.models.query'

This is stripped down from a more reasonably-sized file that actually did things, but it seems to be the imports themselves that triggered the issues.

I think this must be some kind of import-order issue.

(I forget why I was ignoring both lines, but it doesn't seem to really have a tangible effect on the output.)

Hi, @dmoisset!

I really like the initiative taken by you and your collegues over at Machinalis. Static type checking for Django on a general basis would be great!

For the moment it is really difficult to investigate the state of static type checking in the Django community. When searching around I have found this repository and several Google usergroup threads heavily involving you, but more recent information is hard to come by.

Is it possible to adress this in the README in this repository? Questions I have are:

• Are there any plans for pulling these stubs into the official python/typeshed repository?
• Or is it still the plan to pursue pulling this into upstream Django?
• What has been your general impression of the Django maintainers interest in doing so?
• Is the plan to wait for Django 2.0, where Python version 3 can be assumed?

Thanks, Jakob

In order to develop any project, automated testing is essential. I reckon the type stubs can be tested by creating a directory with example files, and by testing the output of mypy after running mypy on those files. We can then ensure that certain symbols are stubbed, that certain types are inferred, etc.

I have some modified stubs for QuerySet and Manager so they accept type parameters. This makes the following possible.

for foo in Foo.objects.all(): # The type of foo is inferred as Foo

Using it requires stubbing models like so.

# foo.py
from django.db import models


class Foo(models.Model):
    bar = models.CharField(max_length=255)

# foo.pyi
from django.db import models


class Foo(models.Model):
    objects = ... # type: models.Manager['Foo']
    bar = ... # type: str

Would you be interested in adding this to the project if I create a pull request?