Django middleware to remove trailing slashes

redirect.py

from django import http
from django.conf import settings
from django.core import urlresolvers
from django.core.exceptions import ImproperlyConfigured
from django.utils.deprecation import MiddlewareMixin


class AppendOrRemoveSlashMiddleware(MiddlewareMixin):
    """
    This middleware removes a given trailing slash if the resulting path is
    valid. It doesn't change admin-URLs.
    Inspiration: https://github.com/dghubble/django-unslashed/blob/master/
                 unslashed/middleware.py
    """

    def process_request(self, request):
        new_url = old_url = request.path_info
        if getattr(settings, 'APPEND_SLASH'):
            raise ImproperlyConfigured("APPEND_SLASH may not both be True if "
                                       "this middleware is used.")
        # Remove trailing slash if the URL has one except for some url-parts
        append_parts = ['/admin']
        append = False
        for sp in append_parts:
            if sp in old_url:
                append = True
        if append and not new_url.endswith('/'):
            new_url += '/'
        elif not append and new_url.endswith('/'):
            new_url = new_url[:-1]
        if new_url != old_url:
            urlconf = getattr(request, 'urlconf', None)
            if urlresolvers.is_valid_path(new_url, urlconf):
                # keep given query-params
                qs = request.META.get('QUERY_STRING', False)
                if qs:
                    new_url += '?' + qs
                if settings.DEBUG and request.method == 'POST':
                    raise RuntimeError(
                        ("You called this URL via POST, but the URL ends in a "
                         "slash. Django can't redirect to the non-slash URL "
                         "while maintaining POST data. Change your form to "
                         "point to '%s' (without a trailing slash).") %
                        (new_url))
                return http.HttpResponsePermanentRedirect(new_url)
        return