diff --git a/django/middleware/common.py b/django/middleware/common.py index b705f72b81..3d55baebde 100644 --- a/django/middleware/common.py +++ b/django/middleware/common.py @@ -5,7 +5,9 @@ from django.conf import settings from django.core.exceptions import PermissionDenied from django.core.mail import mail_managers from django.urls import is_valid_path -from django.utils.cache import get_conditional_response, set_response_etag +from django.utils.cache import ( + cc_delim_re, get_conditional_response, set_response_etag, +) from django.utils.deprecation import MiddlewareMixin from django.utils.encoding import force_text from django.utils.http import unquote_etag @@ -113,7 +115,7 @@ class CommonMiddleware(MiddlewareMixin): if self.should_redirect_with_slash(request): return self.response_redirect_class(self.get_full_path_with_slash(request)) - if settings.USE_ETAGS: + if settings.USE_ETAGS and self.needs_etag(response): if not response.has_header('ETag'): set_response_etag(response) @@ -130,6 +132,13 @@ class CommonMiddleware(MiddlewareMixin): return response + def needs_etag(self, response): + """ + Return True if an ETag header should be added to response. + """ + cache_control_headers = cc_delim_re.split(response.get('Cache-Control', '')) + return all(header.lower() != 'no-store' for header in cache_control_headers) + class BrokenLinkEmailsMiddleware(MiddlewareMixin): diff --git a/tests/middleware/tests.py b/tests/middleware/tests.py index f9ef951b44..07e1d4ea5a 100644 --- a/tests/middleware/tests.py +++ b/tests/middleware/tests.py @@ -275,6 +275,20 @@ class CommonMiddlewareTest(SimpleTestCase): res = StreamingHttpResponse(['content']) self.assertFalse(CommonMiddleware().process_response(req, res).has_header('ETag')) + @override_settings(USE_ETAGS=True) + def test_no_etag_no_store_cache(self): + req = HttpRequest() + res = HttpResponse('content') + res['Cache-Control'] = 'No-Cache, No-Store, Max-age=0' + self.assertFalse(CommonMiddleware().process_response(req, res).has_header('ETag')) + + @override_settings(USE_ETAGS=True) + def test_etag_extended_cache_control(self): + req = HttpRequest() + res = HttpResponse('content') + res['Cache-Control'] = 'my-directive="my-no-store"' + self.assertTrue(CommonMiddleware().process_response(req, res).has_header('ETag')) + @override_settings(USE_ETAGS=True) def test_if_none_match(self): first_req = HttpRequest()