Add check that all items in url patterns are url instances

[Alasdair Nicol]

If you include a tuple instead of a url() instance in your urlpatterns, the checks framework throws an error which isn't very helpful.

urlpatterns = ['', # leading string might be left by users converting from patterns() in earlier Django versions
    (r'^$', my_view),
    url(r'^admin/', admin.site.urls),
]

  File "site-packages/django/core/checks/urls.py", line 67, in check_pattern_startswith_slash
    regex_pattern = pattern.regex.pattern
AttributeError: 'tuple' object has no attribute 'regex'

I suggest that we should create a new warning if the pattern is not a url() instance.

[Alasdair Nicol]

I thought this might be a good ticket if somebody's looking for a ticket during the Djangocon EU sprints. If it's not picked up, then I'll take a look at it next week.

[Tim Graham]

Left comments for improvement on the ​PR.

[Alasdair Nicol]

I've created a new pr, which builds on burhan's work.

​https://github.com/django/django/pull/6514

[Alasdair Nicol]

Sorry for changing the patch after it had been reviewed. I've added a couple more patches to the pull request

• Added explicit test that URL checks are recursive, and simplified other url configs
• Added hints when users have a string or tuple instead of a url() instance

I think the text of the hints could be improved. I'm not 100% sure that the tuple hint is necessary - maybe saying the main warning 'Ensure that urlpatterns is a list' is enough.

[Tim Graham <timograham@…>]

In eb5d7bc2:

Fixed #26440 -- Added a warning for non-url()s in urlpatterns.

Thanks Burhan Khalid for the initial patch and knbk/timgraham
for review.