#9318: "Virtual" behaviour for signal dispatcher and model inheritance
-------------------------------------+-------------------------------------
Reporter: Alexander Artemenko | Owner: (none)
Type: Bug | Status: new
Component: Core (Other) | Version: 1.0
Severity: Normal | Resolution:
Keywords: model inheritance, | Triage Stage: Accepted
signals, dispatch, proxy, |
subclass |
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Aymeric Augustin):
* type: New feature => Bug
Comment:
I hit this bug today.
It's really a silent data loss issue: creating a proxy model shouldn't
disable behavior of the original model.
I'm applying the following patch to Django until this is resolved:
{{{
--- a/django/db/models/base.py 2016-12-07 17:09:16.000000000 +0100
+++ b/django/db/models/base.py 2016-12-07 17:13:18.000000000 +0100
@@ -810,13 +810,12 @@
using = using or router.db_for_write(self.__class__,
instance=self)
assert not (force_insert and (force_update or update_fields))
assert update_fields is None or len(update_fields) > 0
- cls = origin = self.__class__
- # Skip proxies, but keep the origin as the proxy model.
+ cls = self.__class__
if cls._meta.proxy:
cls = cls._meta.concrete_model
meta = cls._meta
if not meta.auto_created:
- signals.pre_save.send(sender=origin, instance=self, raw=raw,
using=using,
+ signals.pre_save.send(sender=cls, instance=self, raw=raw,
using=using,
update_fields=update_fields)
with transaction.atomic(using=using, savepoint=False):
if not raw:
@@ -829,7 +828,7 @@
# Signal that the save is complete
if not meta.auto_created:
- signals.post_save.send(sender=origin, instance=self,
created=(not updated),
+ signals.post_save.send(sender=cls, instance=self,
created=(not updated),
update_fields=update_fields, raw=raw,
using=using)
save_base.alters_data = True
}}}
IMO this is the correct way to fix the issue. I understand the concern
about backwards compatibility but I have a hard time figuring out a
realistic scenario where developers would purposefully rely on this bug.
--
Ticket URL: <https://code.djangoproject.com/ticket/9318#comment:31>
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