the reverse function does not work in the current application, which was included in the URL using namespace

[blins]

in app/urls.py

urlpatterns = [
    url(r'^$', Index.as_view(), name = 'index'),
    url(r'^all/$', All.as_view(), name = 'all'),
]

in project urls.py

...
    path('app/', include('app.urls', namespace='app')),
...

and in index template app/index.html

{%url all %}

function produces an error "NoReverseMatch at /app/. Reverse for 'all' not found. 'all' is not a valid view function or pattern name."

[blins]

patch

[Tim Graham]

When I setup ULRconfs as you describe, I see "ImproperlyConfigured: Specifying a namespace in include() without providing an app_name is not supported. Set the app_name attribute in the included module, or pass a 2-tuple containing the list of patterns and app_name instead." Maybe the steps to reproduce aren't complete... can you provide a sample project?

[blins]

Sample project

[blins]

I add project.zip in attachements

[Carlton Gibson]

See the docs on ​Reversing namespaced URLs.

Basically you need to include the namespace when using reverse (or the url template tag).

You'll want this:

{%url 'app:all' %}

Also: You've included the app_name in your app/urls.py so your call to include already provides an application_namespace. It's not necessary here to use the namespace parameter as well. (This adds an instance_namespace, which you very likely don't need.)

It's worth reviewing the whole ​URL Namespaces section slowly, and the ​`include()` docs to make sure you're clear on the behaviour here.