#17914: reverse() does not support namespaced view references
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Reporter: Bradley Ayers <bradley.ayers@…> | Owner: nobody
Type: Bug | Status: new
Component: Core (URLs) | Version: 1.3
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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It's not possible to reverse a URL by passing a function reference to
reverse()
that's hooked into the URLconf under a namespace.
Consider the trivial Django project (that doesn't work):
{{{
# urls.py
from django.conf.urls.defaults import patterns, include
from django.core.urlresolvers import reverse
from django.http import HttpResponse
def view(request):
# Return the URL to this view
return HttpResponse(reverse(view))
level2 = patterns('',
(r'^2/', view)
)
urlpatterns = patterns('',
(r'^1/', include(level2, namespace="foo"))
)
}}}
Removing ``, namespace="foo"`` will make it work.
My understanding of why this happens, is that `reverse()` traverses
`RegexURLResolver`s
*only* for strings. Function references are passed directly to the root
`RegexURLResolver.reverse`
method.:
{{{
# from django/core/urlresolvers.py ~ line 432
if not isinstance(viewname, basestring):
view = viewname
else:
# <snip> -- resolver traversal happens here to honor namespaces
# `resolver` is reassigned to last RegexURLResolver in namespace chain
return iri_to_uri(resolver._reverse_with_prefix(view, prefix, *args,
**kwargs))
}}}
Obviously traversing namespaces isn't possible for a function reference,
so what's needed is to add *all* descendent view references into each
`RegexURLResolver`'s
`reverse_dict` dictionary.
Populating `reverse_dict` is lazy and happens on first access, the work is
performed in `RegexURLResolver._populate`:
{{{
# django/core/urlresolvers.py ~ line 237
def _populate(self):
# <snip>
for pattern in reversed(self.url_patterns):
# <snip>
if isinstance(pattern, RegexURLResolver):
if pattern.namespace:
# <snip> -- tldr `self.reverse_dict` isn't populated,
`pattern` (the
# RegexURLResolver) is instead stored in
`self.namespace_dict`
else:
# <snip> -- tldr `self.reverse_dict` *is* populated with
the keys
# being the name of each URL (or the function
reference)
# defined in this level. (i.e. only children,
not all descendants)
else:
# <snip> -- tldr `self.reverse_dict` is again populated
}}}
This combination of behaviour by `RegexURLResolver._populate` and
`reverse()`
leads to the problem.
--
Ticket URL: <https://code.djangoproject.com/ticket/17914>
Django <https://code.djangoproject.com/>
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