Make RegexURLResolver easier to subclass

[Kenneth Arnold]

Referencing ​the django-developers discussion, here's some simple patches to make the URL resolver easier to customize.

First is a nearly minimal patch to convert the url_patterns property to an accessor, get_url_patterns, to ease subclassing, and make the other methods use that consistently instead of duplicating its functionality. With only this patch you can make your own URL resolver without duplicating code, but it's still not clean.

The second patch cleans up the situation by abstracting the core functionality of a regex URL resolver into BaseRegexURLResolver.

The third patch is an example of how newforms-admin might use this for URL dispatching. I don't have a deep understanding about what's going on, so treat what I did just as an example. Perhaps the cleanest way to accomplish some of what the old ad-hoc resolver did is to override resolve, and if super().resolve returns None, do the ad-hoc stuff.

You'd use a custom resolver in your urlconf like this:

urlpatterns += [AdminSite(r'^admin/')]

i.e., like a normal include (at least, what that include looks like under the hood).

The newforms-admin change would be backwards-incompatible, so if people think it's a good idea, it should get a separate ticket.

About the accessor: properties don't inherit well. Could add a url_patterns = property(lambda self: self.get_url_patterns()) if that's not too ugly.

[Kenneth Arnold]

Patch 2: extract base functionality

[Kenneth Arnold]

Example nfa change (Example Only)

[Kenneth Arnold]

nearly minimal patch

[Erik Allik]

Wouldn't this also solve the issue of not being able to reverse or {% url %} "into" the admin interface?

[Alex Gaynor]

Yes, but so does #6470

[Erik Allik]

I cannot see how. If #6470 was applied, would I be able to do {% url admin_edit_view mymodel %}?

[Alex Gaynor]

me of a few years ago was silly, any way to better organize the code is a good idea.

[Mariusz Felisiak]

It seems that this ticket is not valid after #28593.