[Django] #30019: Add __class_getitem__ method to managers and querysets
Django
-------------------------------------+-------------------------------------
Reporter: mkurnikov | Owner: nobody
Type: New | Status: new
feature |
Component: Database | Version: master
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
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I'm working on a pep561 stubs package for Django here
https://github.com/mkurnikov/django-stubs
In order to be able to fully support managers as a generics, one needs to
write
{{{
from django.db import models
class UserManager(models.Manager[User]):
def get_or_404(self) -> User:
pass
class User(models.Model):
objects = UserManager()
}}}
but it fails at {{{ models.Manager[User] }}}.
There's a new method {{{ __class_getitem__ }}} in python3.7 to get around
that, defined in pep560
https://www.python.org/dev/peps/pep-0560/
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Ticket URL: <https://code.djangoproject.com/ticket/30019>
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The Web framework for perfectionists with deadlines.
Django
-------------------------------------+-------------------------------------
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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* status: new => assigned
* owner: nobody => Greg
--
Ticket URL: <https://code.djangoproject.com/ticket/30019#comment:1>
Django
-------------------------------------+-------------------------------------
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Greg):
Is this the error you are getting:
NameError: name 'User' is not defined
If not, can you please let me know what the error is?
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Ticket URL: <https://code.djangoproject.com/ticket/30019#comment:2>
Django
-------------------------------------+-------------------------------------
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Comment (by Maxim Kurnikov):
{{{TypeError: 'type' object is not subscriptable}}}
Look at
https://www.python.org/dev/peps/pep-0560/#class-getitem
and how it was implemented before with {{{GenericMeta}}}
https://www.python.org/dev/peps/pep-0484/#user-defined-generic-types
Minimal repro should be this one
{{{
from django.db import models
class UserManager(models.Manager['User']):
pass
class User(models.Model):
objects = UserManager()
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/30019#comment:3>
Django
-------------------------------------+-------------------------------------
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
* cc: Herbert Fortes (added)
--
Ticket URL: <https://code.djangoproject.com/ticket/30019#comment:4>
Django
-------------------------------------+-------------------------------------
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Comment (by Greg W):
I got {{{ __class_getitem__}}} implemented. However, I am having an
issue with {{{models.Manager['User']}}}
Isn't {{{'User'}}} just a string which {{{__class_getitem__}}} would not
be valid on? I think the idea is to index the class User, but this class
has not been defined prior to {{{Manager[User]}}}.
Let me know if I am off base.
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Ticket URL: <https://code.djangoproject.com/ticket/30019#comment:5>
Django
-------------------------------------+-------------------------------------
Component: Database layer | Version: master
(models, ORM) |
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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* status: assigned => closed
* resolution: => needsinfo
Comment:
Hi Maxim.
I'm going to close this as needsinfo right now. Not because I'm against it
but because it's part of the wider discussion around Type Hinting in
Django.
I see you posted to the Django-Developers thread about this:
https://groups.google.com/d/topic/django-developers/trTEbURFhEY/discussion
Can I ask you to add your effort there? I think there's a group of people
who are there or there-abouts with this: as ever, it just needs a bit of a
nudge.
(There was talk of a DEP, of a working groups, of... — we just need to get
there.)
Thanks.
I'll post there to try and re-liven it.
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Ticket URL: <https://code.djangoproject.com/ticket/30019#comment:6>
Django
-------------------------------------+-------------------------------------
Type: New feature | Status: closed
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution: needsinfo
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Tim Graham):
(And #29299 is the Someday/Maybe ticket for adding type hints and variable
annotations.)
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Ticket URL: <https://code.djangoproject.com/ticket/30019#comment:7>