#31069: Change in behavior for optional re matches.
--------------------------------+------------------------------------
Reporter: Terence Honles | Owner: nobody
Type: Bug | Status: new
Component: Documentation | Version: 3.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by Terence Honles:
Old description:
> I am mainly pointing this out as it probably should have been called out
> as a breaking change from Django 2.X to 3.X (And I think the release
> notes should probably be adjusted if the old functionality is not to be
> restored). You can probably argue either way about if this is a bug since
> it's coming from re's `match.groupdict()`. It's related to
> https://code.djangoproject.com/ticket/31061 and caused by
> https://code.djangoproject.com/ticket/26431 /
> https://github.com/django/django/pull/11477
>
> The test is the following:
>
> {{{
> from django.urls import re_path
>
> def view(request, optional1, optional2): ...
>
> urlpatterns = [
> re_path(r'^(?P<optional1>\w+/)(?:(?P<optional2>\w+)/)', view)
> ]
> }}}
>
> For Django 2.X this would work as expected because named captures are
> returned even if they are `None`, however in Django 3.0 this would raise
> an error because positional parameter `optional2` is no longer provided.
> (i.e. `view() missing 1 required positional argument: 'optional2'`)
>
> You can argue that `optional2` should actually have had a default all
> along, but it didn't before and code may unexpectedly break because it is
> now required.
>
> I'm not very familiar with https://code.djangoproject.com/ticket/26431,
> but I think if possible it probably should have been fixed at a different
> level.
New description:
I am mainly pointing this out as it probably should have been called out
as a breaking change from Django 2.X to 3.X (And I think the release notes
should probably be adjusted if the old functionality is not to be
restored). You can probably argue either way about if this is a bug since
it's coming from re's `match.groupdict()`. It's related to
https://code.djangoproject.com/ticket/31061 and caused by
https://code.djangoproject.com/ticket/26431 /
https://github.com/django/django/pull/11477
The test is the following:
{{{
from django.urls import re_path
def view(request, optional1, optional2): ...
urlpatterns = [
re_path(r'^(?P<optional1>\w+/)(?:(?P<optional2>\w+)/)?', view)
]
}}}
For Django 2.X this would work as expected because named captures are
returned even if they are `None`, however in Django 3.0 this would raise
an error because positional parameter `optional2` is no longer provided.
(i.e. `view() missing 1 required positional argument: 'optional2'`)
You can argue that `optional2` should actually have had a default all
along, but it didn't before and code may unexpectedly break because it is
now required.
I'm not very familiar with https://code.djangoproject.com/ticket/26431,
but I think if possible it probably should have been fixed at a different
level.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/31069#comment:5>
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