Errors when reversing admin URLs when custom ModelAdmin doesn't provide model add/change URLs

[Ramiro Morales]

(Originally reported here)

Commit r16857 introduced a backward incompatible behavior of the admin app's master index and per-app index views.

The commit introduces changes in the template context building process that assume add and change permissions on models are always present when it is going to check for them. This fails with projects where these permissions might have been completely removed.

[Ramiro Morales]

Actually, I can't reproduce this, i.e. cant create a regression test.

Things tried:

• Removing the add Permission mode instance completely associated with a given model
• Returning False from the model's ModelAdmin has_add_permission() and
• Explicitly not granting the needed permission to the test user

And no NoReverseMatch exception gets triggered as originally reported here. I'm attaching the WIP patch for the tests and closing this worksforme.

I'm not going to change anything until we can reproduce the failing condition. It would be great if user kingtut that posted that comment can give us additional feedback, bonus points if he can modify the test case to fail.

[Jannis Leidel]

With regard to the original bug report, there is a fix out there, at least for django-mailchimp: ​https://github.com/JohnRandom/django-mailchimp/commit/a8bfef1581ce43a2ea6f56a3707f14a611596148

[Ramiro Morales]

Avoid NoRevereMatch when a custom ModelAdmin.get_urls() doesn't call super()

[Ramiro Morales]

In [17237]:

Stopped unconditionally reversing admin model add/change URLs.

Starting with [16857] this could cause HTTP 500 errors when
ModelAdmin.get_urls() has been customized to the point it doesn't
provide these standard URLs.

Fixes #17333. Refs #15294.