error: DateTimeField is nullable but its generic get type parameter is not optional

[vinko-rx]

Bug report

What's wrong

After upgrading to 5.2.1, I am getting the following issue for any field that has null=True argument.

error: DateTimeField is nullable but its generic get type parameter is not optional  [misc]
...
error: ForeignKey is nullable but its generic get type parameter is not optional  [misc]
...
error: CharField is nullable but its generic get type parameter is not optional  [misc]

As a temporary measure, I downgraded to 5.2.0 and mypy to 1.15.0.

How is that should be

System information

• OS: MacOS Sequoia 15.5; Ubuntu 24.04.2 (GitHub Actions)
• python version: 3.13.4
• django version: 5.2.3
• mypy version: 1.16.1
• django-stubs version: 5.2.1
• django-stubs-ext version: 5.2.1

[sobolevn]

Do you have a repro?

[martin-thoma]

I have the same issue after upgrading to 5.2.1 (in a non-public repo).

Also for OneToOneField

[UnknownPlatypus]

A minimal snippet to reproduce would be very useful

[martin-thoma]

I tried to do that: https://github.com/martin-thoma/django-stubs-2724

Interestingly, this does NOT fail

[martin-thoma]

Do you think it could be related to other installed packages? django-money caused issues in the past, IIRC

My real app has those:

INSTALLED_APPS = [
    "django.contrib.admin",
    "django.contrib.auth",
    "django.contrib.contenttypes",
    "django.contrib.sessions",
    "django.contrib.messages",
    "django.contrib.staticfiles",
    "core", # my project
    "corefoo",  # another private one
    # Not added to the test so far:
    "oauth2_provider",
    "rest_framework",
    "polymorphic",
    "djmoney",
    "drf_spectacular",
    "django_extensions",
    "constance",
]

my mypy config:

[mypy]
show_error_codes = True
warn_unused_ignores = False
show_traceback = True
ignore_missing_imports = True
python_version = 3.13
files = mysettings,core
plugins = mypy_django_plugin.main, mypy_drf_plugin.main
strict_optional = True

[mypy.plugins.django-stubs]
django_settings_module = mysettings.settings_base

[martin-thoma]

@vinko-rx Does your private project have some overlap with my projects INSTALLED_APPS or mypy config?

[BMourguesFieldbox]

I have the same issue with nullable fields

django-stubs = "~5.2.1"
django-stubs-ext = ">=5.2.1"

Mypy config:

[mypy]
python_version = 3.12
ignore_missing_imports = True
warn_redundant_casts = True
warn_unused_ignores = True
strict_optional = False
implicit_reexport = True
plugins =
    mypy_django_plugin.main,
    mypy_drf_plugin.main
mypy_path = backend/foo

[mypy-*.migrations.*]
ignore_errors = True

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

[martin-thoma]

@BMourguesFieldbox Can you adjust https://github.com/martin-thoma/django-stubs-2724 so that the issue can be reproduced?

[malo-malo]

For reference the issue seems to be linked to mypy version 1.16.1.
In our repo we have django stubs version 5.1.3 with mypy 1.15.0, which works fine. However bumping mypy to 1.16.0 (while keeping django stubs 5.1.3) leads to a bunch of ... is nullable but its generic get type parameter is not optional errors (on all kind of fields)

[martin-thoma]

But that seems to be not the whole story. Because https://github.com/martin-thoma/django-stubs-2724 has mypy==1.16.1 and django-stubs==5.2.1. It does not fail. Even with django-stubs==5.1.3

[malo-malo]

True, I tried adding all the dependencies and installed apps from my repo to that example one, and still did not manage make mypy fail on it

[malo-malo]

I managed to reproduce on your repo, by just adding the strict_optional = false config flag. We use that flag in our repo so I suspect that's the cause. I'll try finding out which mypy commit introduced the regression.

martin-thoma/django-stubs-2724#1

[malo-malo]

I did a git bisect between mypy versions 1.15.0 and 1.16.0 on the minmal reproduction, which gave me the following commit as the one that introduced the regression

python/mypy@4629de4
Related issue python/mypy#7724

[martin-thoma]

You're awesome @malo-malo <3

We have the following in our tox.ini in the private project I mentioned:

[mypy]
strict_optional = True

[mypy-core.*]
strict_optional = False <------------------

And all failing parts are in mypy core. So I guess we have the same issue / same root cause.