Add a helpful exception message when ListView.get_queryset() returns None

[Bjorn Kristinsson]

One of my ListViews suddenly started raising TemplateDoesNotExist with a rather cryptic (to me) message:

Template-loader postmortem
 
Django tried loading these templates, in this order:
 
Using engine :
This engine did not provide a list of tried templates.

It took me a while to realise this was because my get_queryset wasn't returning anything. It did some filtering based on user settings, and I didn't have a fallback for when none of the filtering steps applied.

Thought it might be helpful to have a better message is no template names are found and object_list is None. Suggesting: "Expected a queryset, but found None. Please check that <cls>.get_queryset() returns a queryset." Pull request coming up.

[Bjorn Kristinsson]

Created a pull request, ​https://github.com/django/django/pull/9255, not entirely sure why the tests are failing.

[Bjorn Kristinsson]

Oki, guess someone else than me needs to move this forward. The PR is passing tests now, comments addressed - but someone else needs to accept or reject it.

[Herbert Fortes]

Hi,

I read the patch and ran the tests.

Ran 202 tests in 3.730s
OK

It seems that the patch does what the author wants. If
there is no information at all raise 'ImproperlyConfigured'.

patch ok
tests ok
docs ok

I am not changing to 'Ready for checkin' because this is
my first time doing a review.

Regards,
Herbert

[Tim Graham <timograham@…>]

In ac6a4eb:

Fixed #28719 -- Added a helpful exception if MultipleObjectTemplateResponseMixin doesn't generate any template names.