contenttypes.views.shortcut fails if a FK to Site returns None

[Jaap Roes]

The contenttypes.views.shortcut assumes that a FK to Site is never nullable. Causing it to raise an AttributeError when the field actually is null. This is happens e.g. when clicking the "view on site" link in the admin on an object that has an empty Site relation.

# Next, look for a many-to-one relationship to Site.
if object_domain is None:
    for field in obj._meta.fields:
        if field.rel and field.rel.to is Site:
            try:
                object_domain = getattr(obj, field.name).domain
            except Site.DoesNotExist:
                pass

Either explicitly checking that the result of the getattr call is not None or catching a AttributeError will fix this.

[Fabien Schwob]

Created a PR. Feedback needed, it's my first PR to Django.
​https://github.com/django/django/pull/5986

[Claude Paroz]

​PR (test failures)

[dani poni]

Created a PR to fix the test problem as suggested by claudep.
​https://github.com/django/django/pull/6427

[Tim Graham]

Left some comments for improvement on the updated PR.

[Jaap Roes]

Sorry, I'm of the opinion that raising a 404 is the wrong solution. All other exceptions that are caught (IndexError, Site.DoesNotExist) are silently ignored, I think the same should be done for a None value.

The reason I stumbled upon this issue in the first place is that in my use case objects with no explicit site relation are available on all sites. So raising a 404 would be not be much of an improvement over raising a 500 ;-).

[Claude Paroz]

Makes sense.

[dani poni]

Changed the PR according to jaap3's suggestion

[Tim Graham]

Left a few cosmetic comments and tests aren't passing on databases other than SQLite.

[Tim Graham <timograham@…>]

In d29d11b:

Fixed #26085 -- Fixed contenttypes shortcut() view crash with a null fk to Site.

Thanks Fabien Schwob for the initial patch.

[Tim Graham <timograham@…>]

In 2a9bcb5:

Refs #26085, #11505 -- Cleared Site cache in contenttypes_tests.