Auto register Django auth models using custom admin site

1. Create your own AdminSite with a simple __init__() override.
2. Import your admin in urls.py.

Replacing the Django Admin and getting the autodiscover() behavior is possible with minimal effort. Here's a project structure generated in the typical django-admin startproject project fashion:

project/
    manage.py
    project/
        __init__.py
        settings.py
        urls.py
        wsgi.py
        admin.py  # CREATE THIS FILE

project/admin.py: (I think it makes the most sense to do this at the project level.)

from django.contrib.admin import *  # PART 1

class MyAdminSite(AdminSite):
    site_header = "My Site"

    def __init__(self, *args, **kwargs):
        super(MyAdminSite, self).__init__(*args, **kwargs)
        self._registry.update(site._registry)  # PART 2

site = MyAdminSite()

project/urls.py (snippet):

from . import admin  # PART 3

urlpatterns = [
    url(r'^admin/', admin.site.urls),
]

Part 1 is simple Python. By importing everything from django.contrib.admin into your namespace, it acts as a drop-in replacement. I suppose you don't have to do this, but it helps preserve expectations. Part 3, simply connect up your admin. Part 2 is the real trick. As the documentation says, autodiscover() is called to do the work. All autodiscover does is go through INSTALLED_APPS attempting to import a file called admin.py. Importing runs the code of course and that code is doing the same thing you do to register models (example by decorator and example by method). No magic. You don't have to register your models with your customized admin (as the documentation says).

Autodiscover looks smarter than it is with its register_to kwarg. That indicates you could call autodiscover() yourself passing your own admin. Nope; there's no wiring connected there (future feature?). The assignment happens here and is fixed to the native AdminSite instance here (or here using the decorator). Django contrib models register to that instance and so will any third-party libraries. It's not something you can hook into.

Here's the trick though, _registry is just a dictionary mapping. Let Django autodiscover all the things and then just copy the mapping. That's why self._registry.update(site._registry) works. "self" is your customized AdminSite instance, "site" is Django's instance and you can register your models with either.

(Final note: If models are missing, it's because of import order. All the registration to Django's AdminSite needs to happen before you copy _registry. Registering directly to your customized admin is probably the easiest thing.)

The Django docs suggest using SimpleAdminConfig with a custom admin site.

INSTALLED_APPS = (
    ...
    'django.contrib.admin.apps.SimpleAdminConfig',
    ...
)

That prevents the models being registered with the default AdminSite.

The docs seem to assume that you will import the models individually and add them to your custom admin site:

from django.contrib.auth.models import Group, User
from django.contrib.auth.admin import GroupAdmin, UserAdmin

admin_site.register(Group, GroupAdmin)
admin_site.register(User, UserAdmin)

This would be very repetitive if you have models in many apps. It doesn't offer any advice how to automatically register models from all your apps with your custom site.

You could try monkey patching admin, and replacing admin.site with your own.

from django.contrib import admin
admin.site = OptiAdmin(name='opti_admin')

Then, when code called admin.site.register(), it would register the model with your admin site. This code would have to run before any models were registered. You could try putting it in the AppConfig for your app, and make sure that your app is above django.contrib.admin.