Reverse for 'tagged' with arguments '('',)' not found. 1 pattern(s) tried: ['^tag/(?P<slug>[-\w]+)/$']

Question

I keep getting this error message:

Reverse for 'tagged' with arguments '('',)' not found. 1 pattern(s) tried: ['\^tag/\(\?P(?P[^/]+)\[\-\\w\]\+\)/\$$']

when trying to load my base.html, because of an anchor tag. I have looked at other posts with the same issue, but I still don't know where I'm going wrong.

views.py

class TagIndexView(TagMixin, ListView):
    template_name = 'post/index.html'
    model = Post
    paginate_by = '10'
    context_object_name = 'posts'

    def get_queryset(self):
        return Post.objects.filter(tags__slug=self.kwargs.get('slug'))

def tagged(request):
    return render(request, 'blog/tagged.html', {'title': 'Tagged'})

urls.py

path(r'^tag/(?P<slug>[-\w]+)/$',TagIndexView.as_view, name='tagged')

base.html
The anchor tag:

<li class="list-group-item"><a href="{% url 'tagged' tag.slug %}">Tags</a></li>

But I keep getting a NoReverseMatch. In the anchor tag I have tried "tag.slug", "tag.id", "tag.pk" and some others.

Answer 1

1. Use re_path() instead of path() for regular expressions.

   Reference: https://docs.djangoproject.com/en/3.2/topics/http/urls/#using-regular-expressions

2. Use [-\w]* (0 or more) instead of [-\w]+ (1 or more) to allow empty string ('',).

3. Call .as_view with .as_view() to create the view function.

#  path(r'^tag/(?P<slug>[-\w]+)/$', TagIndexView.as_view,   name='tagged')
re_path(r'^tag/(?P<slug>[-\w]*)/$', TagIndexView.as_view(), name='tagged')