#16368: Custom sites model overridden by contrib.sites.model.Site
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Reporter: | Owner: nobody
briehan.lombaard@… | Status: reopened
Type: Bug | Component: contrib.sites
Milestone: | Severity: Normal
Version: SVN | Keywords:
Resolution: | Has patch: 0
Triage Stage: Accepted | Needs tests: 0
Needs documentation: 0 | Easy pickings: 0
Patch needs improvement: 0 |
UI/UX: 0 |
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Changes (by lakin):
* status: closed => reopened
* resolution: duplicate =>
Comment:
I'm re-opening this as I feel that I can better explain what is happening
here. It is the combination of a few different, but important aspects and
there may be a few different fixes that are in order.
First off - from the sites documentation -
https://docs.djangoproject.com/en/dev/ref/contrib/sites/#requestsite-
objects There are parts of django that use the sites framework even if
it's not installed. So ultimately, there valid use cases where the sites
app is NOT installed, but it IS imported. This is an important
distinction. In these case, I feel that it is reasonable that one should
be able to make a new sites app with a model called Site.
The above is not a bug, in and of itself. However, when the sites app is
imported, its models.py is also imported. When the models.py is imported
the ModelBase metaclass runs and prepares this model. It also caches this
model for future use so that subsequent imports don't go through the
costly process of preparing the model a second time. However, it caches
the model based on the app_label and model class name, which in this case
is 'sites.Site'. When the new, custom app is imported, the same process
occurs. However - this time around it notices that it already prepared a
'sites.Site' - so rather than making a new one, it returns a reference to
the old one. However, in this particular case it will always the wrong
reference. It will always be a reference to the non-used
django.contrib.sites.models.Site model instead of the custom one. For
reference, this is the code that does the caching:
https://code.djangoproject.com/browser/django/trunk/django/db/models/base.py#L91
There are many potential solutions to this - but I'm not sure which is the
appropriate one. Ultimately I feel that django's use of app_labels as
unique across all installed apps is the actual errant decision - but this
ticket isn't about fixing that. This ticket is about fixing it so that
one can use a custom sites.models.Site model when the
django.contrib.sites.models.Site is not being used.
I think the appropriate usage would be to update it so that the Meta class
for django's models only caches models that it has prepared when they are
part of an installed application. If they are not part of an installed
application then they should be ignored.
You can test this using the same attached example, but this time include
django.contrib.admin in the INSTALLED_APPS (which imports sites). Or you
can import the contenttypes app which also uses it.
Does that help explain the issue?
--
Ticket URL: <https://code.djangoproject.com/ticket/16368#comment:15>
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