#32156: Add __class_getitem__ to support runtime type parameters for more
classes
-------------------------------------+-------------------------------------
Reporter: Brady Kieffer | Owner: Brady
| Kieffer
Type: New feature | Status: assigned
Component: Utilities | Version: 2.2
Severity: Normal | Resolution:
Keywords: types, mypy, | Triage Stage:
django-stubs | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Comment (by Brady Kieffer):
Hi Carlton,
Thanks for the speedy response. I guess I just want to preface everything
here by saying I pretty squarely fall into the bucket of being a user of
both `Django` + `django-stubs`. I definitely agree that the code is a bit
boilerplate-y. I don't actually think this is a mypy issue, it's more
about how we choose to reconcile the true implementation of Django with
third party libraries attempting to type it in a simple manner. So, when
it comes to:
{{{
@classmethod
def __class_getitem__(cls, *args, **kwargs):
return cls
}}}
I tend to agree that it's pretty annoying that we have to modify Django to
make it usable with `django-stubs`. In defense of `mypy` and typing in
general, there's a more idiomatic approach to this problem by defining a
class as a `Generic` ([https://mypy.readthedocs.io/en/stable/generics.html
#defining-generic-classes docs for Generics here]). I _believe_ the reason
that adding `Generic` as a base for `QuerySet` + `Manager` was avoided
because it could have an impact downstream but, I don't really know why
this was decided. So, `mypy` would recommend we use `Generic`, which we
likely will not, and it sort of leaves open the question of what should we
reasonably expect to do with Django **if** we want to support third party
typing libraries. I'm not super opinionated, but I would definitely rather
not have to monkeypatch every codebase that uses django-stubs if it can be
avoided. If we do go down this path though, I would agree that your second
point will likely never be satisfied.
Type checking is really cool, and it's saved us from some very weird bugs.
But, it definitely feels like we're in a weird middle ground where there
isn't "the one perfect way" of doing it.
--
Ticket URL: <https://code.djangoproject.com/ticket/32156#comment:3>
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