add prevent_auto flag to cache control

2 files changed, 14 insertions, 5 deletions

diff --git a/pyramid/config.py b/pyramid/config.py
index aa02c3d69..53daf3b56 100644
--- a/pyramid/config.py
+++ b/pyramid/config.py
@@ -1140,6 +1140,12 @@ class Configurator(object):
           tuple as ``http_cache`` with the first element of ``None``, e.g.:
           ``(None, {'public':True})``.
 
+          If you wish to prevent a view that uses ``http_cache`` in its
+          configuration from having its response changed by ``http_cache`` ,
+          set ``response.cache_control.prevent_auto = True`` before returning
+          the response.  This effectively disables any HTTP caching done by
+          ``http_cache`` for that response.
+
         wrapper
 
           The :term:`view name` of a different :term:`view
@@ -2990,7 +2996,9 @@ class ViewDeriver(object):
 
         def wrapper(context, request):
             response = view(context, request)
-            response.cache_expires(seconds, **options)
+            cache_control = response.cache_control
+            if not hasattr(cache_control, 'prevent_auto'):
+                response.cache_expires(seconds, **options)
             return response
 
         return wrapper
diff --git a/pyramid/tests/test_config.py b/pyramid/tests/test_config.py
index ad5e5a89a..d7e62da0a 100644
--- a/pyramid/tests/test_config.py
+++ b/pyramid/tests/test_config.py
@@ -4318,19 +4318,20 @@ class TestViewDeriver(unittest.TestCase):
         self.assertFalse('Expires' in headers)
         self.assertEqual(headers['Cache-Control'], 'public')
 
-    def test_http_cached_view_nonresponse_object_returned_downstream(self):
+    def test_http_cached_view_prevent_auto_set(self):
         from pyramid.response import Response
         response = Response()
+        response.cache_control.prevent_auto = True
         def inner_view(context, request):
             return response
         deriver = self._makeOne(http_cache=3600)
         result = deriver(inner_view)
-        self.assertFalse(result is inner_view)
-        self.assertEqual(inner_view.__module__, result.__module__)
-        self.assertEqual(inner_view.__doc__, result.__doc__)
         request = self._makeRequest()
         result = result(None, request)
         self.assertEqual(result, response) # doesn't blow up
+        headers = dict(result.headerlist)
+        self.assertFalse('Expires' in headers)
+        self.assertFalse('Cache-Control' in headers)
 
     def test_http_cached_view_bad_tuple(self):
         from pyramid.exceptions import ConfigurationError