Fixed #26293 -- Fixed CommonMiddleware to process PREPEND_WWW and APPEND_SLASH independently.

django/middleware/common.py

@@ -54,18 +54,19 @@ class CommonMiddleware(object):
 
         # Check for a redirect based on settings.PREPEND_WWW
         host = request.get_host()
+        must_prepend = settings.PREPEND_WWW and host and not host.startswith('www.')
+        redirect_url = ('%s://www.%s' % (request.scheme, host)) if must_prepend else ''
 
-        if settings.PREPEND_WWW and host and not host.startswith('www.'):
+        # Check if a slash should be appended
-            host = 'www.' + host
-
-            # Check if we also need to append a slash so we can do it all
-            # with a single redirect.
         if self.should_redirect_with_slash(request):
             path = self.get_full_path_with_slash(request)
         else:
             path = request.get_full_path()
 
-            return self.response_redirect_class('%s://%s%s' % (request.scheme, host, path))
+        # Return a redirect if necessary
+        if redirect_url or path != request.get_full_path():
+            redirect_url += path
+            return self.response_redirect_class(redirect_url)
 
     def should_redirect_with_slash(self, request):
         """

docs/releases/1.9.5.txt

@@ -34,3 +34,6 @@ Bugfixes
 * Fixed a crash when using a reverse lookup with a subquery when a
   ``ForeignKey`` has a ``to_field`` set to something other than the primary key
   (:ticket:`26373`).
+
+* Fixed a regression in ``CommonMiddleware`` that caused spurious warnings in
+  logs on requests missing a trailing slash (:ticket:`26293`).

tests/middleware/tests.py

@@ -67,10 +67,8 @@ class CommonMiddlewareTest(SimpleTestCase):
         APPEND_SLASH should redirect slashless URLs to a valid pattern.
         """
         request = self.rf.get('/slash')
-        response = HttpResponseNotFound()
+        r = CommonMiddleware().process_request(request)
-        r = CommonMiddleware().process_response(request, response)
         self.assertEqual(r.status_code, 301)
-        self.assertEqual(r.url, '/slash/')
 
     @override_settings(APPEND_SLASH=True)
     def test_append_slash_redirect_querystring(self):
@@ -301,9 +299,6 @@ class CommonMiddlewareTest(SimpleTestCase):
         request = self.rf.get('/slash')
         request.META['QUERY_STRING'] = force_str('drink=café')
         r = CommonMiddleware().process_request(request)
-        self.assertIsNone(r)
-        response = HttpResponseNotFound()
-        r = CommonMiddleware().process_response(request, response)
         self.assertEqual(r.status_code, 301)
 
     def test_response_redirect_class(self):