id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
17648	Allow `GenericForeignKey` to retreive/store proxy model content type.	Simon Charette	Simon Charette	"The actual `ContentTypeManager`'s `get_for_model` and `get_for_models` methods always return the `ContentType` of the concrete class of a proxy model. This behaviour is causing `GenericForeignKey` to save the concrete class of proxy model and creates inconsistencies in the `ContentTypeManager`'s `get_...` API:
{{{
from django.contrib.auth.models import User
from django.contrib.contenttypes.models import ContentType

class Worker(User):
    class Meta:
      app_label = 'app'
      proxy = True

ct_get_for_model = ContentType.objects.get_for_model(Worker)
ct_natural_key = ContentType.objects.get_by_natural_key('app', 'worker')
assert ct_natural_key == ct_get_for_model # raises AssertionError
}}}

I don't know if it was a design decision (IHMO it's a mistake and a bug) to do so but changing it now would introduce a small backward compatibility issue for any app relying on `get_for_model` directly or indirectly through the use of `GenericForeignKey' since they would now ''benefit'' from getting the exact ct they were referencing.

If I'm not mistaken, by looking at [https://github.com/charettes/django/blob/master/tests/regressiontests/defer_regress/tests.py#L65-71 regressiontests.defer_regress.tests.DeferRegressionTest] and #10738, I assume this was introduced by r10523 to make sure deferred models are handled correctly by `get_for_model`. Checks for proxy reversing should be made against `model._defered` and not `model._meta.proxy'.

A discussion recently emerged of #11154 (which is caused by this behaviour) suggesting to either remove the proxy following routine of `get_for_model(s?)` or to allow passing a flag (`follow_proxy`) to ''opt-in'' for the ''correct'' behaviour.

I'm attaching a simple patch that only replaces the checks in `_get_opts` (and automatically fixes #11154) and I'll be marking the ticket as 'DDN' since it involves a small backward compatibility issue that requires feedbac.
"	New feature	closed	contrib.contenttypes	dev	Normal	fixed	contenttype proxy	charette.s@… danny.adair@… anssi.kaariainen@…	Accepted	1	1	0	1	0	0