#23641: Apps.set_installed_apps causes signals registered with apps as senders
not
to be received
------------------------------+------------------------------------
Reporter: wrwrwr | Owner: nobody
Type: Bug | Status: new
Component: Core (Other) | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by wrwrwr):
Thanks for the quick response. Good news is that scanning the source for
".connect(", "@receiver(" and "sender=" didn't reveal any other cases of
using `AppConfig` as a sender, so for consistency I've only also moved
`post_migrate` registration for `auth` and `contenttypes` to `ready` (both
need to be called for every migration, not just their app migration, so
don't specify any sender to `connect`).
On the other hand, theoretically the issue can be triggered without
directly using `set_installed_apps`; the following test fails as is, but
succeeds if you comment out the `modify_settings` decorator:
{{{#!python
from django.apps import apps
from django.dispatch import Signal, receiver
from django.test import TestCase, modify_settings
some_signal = Signal()
app_label = 'auth' # Something installed.
handler_called = False
@receiver(some_signal, sender=apps.get_app_config(app_label))
def signal_handler(sender, **kwargs):
global handler_called
handler_called = True
@modify_settings(INSTALLED_APPS={})
class Test(TestCase):
def test_handler(self):
some_signal.send(apps.get_app_config(app_label))
self.assertTrue(handler_called)
}}}
This is probably an edge case no one will ever run into, nevertheless the
behavior may be somewhat surprising.
How about adding a note to the docs, say something like:
If you provide an `AppConfig` instance as the sender argument, please
ensure that the signal is registered in `AppConfig.ready` as app configs
can be reinstantiated during testing.
at the [https://docs.djangoproject.com/en/dev/ref/signals/#management-
signals `pre/post_migrate/syncdb` documentation] (seems unlikely that
anyone would use an app config as a sender for any other signal)?
--
Ticket URL: <https://code.djangoproject.com/ticket/23641#comment:2>
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