Fixed #25971 -- Made BrokenLinkEmailsMiddleware ignore APPEND_SLASH redirects.

If APPEND_SLASH=True and the referer is the URL without a trailing '/', then
BrokenLinkEmailsMiddleware shouldn't send an email.

django/middleware/common.py

@@ -162,18 +162,24 @@ class BrokenLinkEmailsMiddleware(object):
     def is_ignorable_request(self, request, uri, domain, referer):
         """
         Return True if the given request *shouldn't* notify the site managers
-        according to project settings or in three specific situations:
+        according to project settings or in situations outlined by the inline
-         - If the referer is empty.
+        comments.
-         - If a '?' in referer is identified as a search engine source.
-         - If the referer is equal to the current URL, ignoring the scheme
-           (assumed to be a poorly implemented bot).
         """
+        # The referer is empty.
         if not referer:
             return True
 
+        # APPEND_SLASH is enabled and the referer is equal to the current URL
+        # without a trailing slash indicating an internal redirect.
+        if settings.APPEND_SLASH and uri.endswith('/') and referer == uri[:-1]:
+            return True
+
+        # A '?' in referer is identified as a search engine source.
         if not self.is_internal_request(domain, referer) and '?' in referer:
             return True
 
+        # The referer is equal to the current URL, ignoring the scheme (assumed
+        # to be a poorly implemented bot).
         parsed_referer = urlparse(referer)
         if parsed_referer.netloc in ['', domain] and parsed_referer.path == uri:
             return True

tests/middleware/tests.py

@@ -417,6 +417,20 @@ class BrokenLinkEmailsMiddlewareTest(SimpleTestCase):
         BrokenLinkEmailsMiddleware().process_response(self.req, self.resp)
         self.assertEqual(len(mail.outbox), 1)
 
+    @override_settings(APPEND_SLASH=True)
+    def test_referer_equal_to_requested_url_without_trailing_slash_when_append_slash_is_set(self):
+        self.req.path = self.req.path_info = '/regular_url/that/does/not/exist/'
+        self.req.META['HTTP_REFERER'] = self.req.path_info[:-1]
+        BrokenLinkEmailsMiddleware().process_response(self.req, self.resp)
+        self.assertEqual(len(mail.outbox), 0)
+
+    @override_settings(APPEND_SLASH=False)
+    def test_referer_equal_to_requested_url_without_trailing_slash_when_append_slash_is_unset(self):
+        self.req.path = self.req.path_info = '/regular_url/that/does/not/exist/'
+        self.req.META['HTTP_REFERER'] = self.req.path_info[:-1]
+        BrokenLinkEmailsMiddleware().process_response(self.req, self.resp)
+        self.assertEqual(len(mail.outbox), 1)
+
 
 @override_settings(ROOT_URLCONF='middleware.cond_get_urls')
 class ConditionalGetMiddlewareTest(SimpleTestCase):