- We now clear ``request.response`` before we invoke an exception view; an

  exception view will be working with a request.response that has not been
  touched by any code prior to the exception.

4 files changed, 37 insertions, 6 deletions

diff --git a/CHANGES.txt b/CHANGES.txt
index ea83827cc..21bea6572 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -45,6 +45,10 @@ Bug Fixes
   inappropriately used ``DBSession.rollback()`` instead of
   ``transaction.abort()`` in one place.
 
+- We now clear ``request.response`` before we invoke an exception view; an
+  exception view will be working with a request.response that has not been
+  touched by any code prior to the exception.
+
 Documentation
 -------------
 
diff --git a/TODO.txt b/TODO.txt
index 84bd14153..56fd89584 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -1,12 +1,6 @@
 Pyramid TODOs
 =============
 
-Must-Have
----------
-
-- Investigate whether we should replace request.response before we invoke an
-  exception view.
-
 Should-Have
 -----------
 
diff --git a/pyramid/router.py b/pyramid/router.py
index 880429424..0a92b5cd5 100644
--- a/pyramid/router.py
+++ b/pyramid/router.py
@@ -162,6 +162,12 @@ class Router(object):
 
                 # handle exceptions raised during root finding and view-exec
                 except Exception, why:
+                    # clear old generated request.response, if any; it may
+                    # have been mutated by the view, and its state is not
+                    # sane (e.g. caching headers)
+                    if 'response' in attrs:
+                        del attrs['response']
+
                     attrs['exception'] = why
 
                     for_ = (IExceptionViewClassifier,
diff --git a/pyramid/tests/test_router.py b/pyramid/tests/test_router.py
index af311cfc2..6cd86901e 100644
--- a/pyramid/tests/test_router.py
+++ b/pyramid/tests/test_router.py
@@ -403,6 +403,33 @@ class TestRouter(unittest.TestCase):
         why = exc_raised(HTTPNotFound, router, environ, start_response)
         self.assertEqual(why[0], 'notfound')
 
+    def test_call_view_raises_response_cleared(self):
+        from zope.interface import Interface
+        from zope.interface import directlyProvides
+        from pyramid.interfaces import IExceptionViewClassifier
+        class IContext(Interface):
+            pass
+        from pyramid.interfaces import IRequest
+        from pyramid.interfaces import IViewClassifier
+        context = DummyContext()
+        directlyProvides(context, IContext)
+        self._registerTraverserFactory(context, subpath=[''])
+        def view(context, request):
+            request.response.a = 1
+            raise KeyError
+        def exc_view(context, request):
+            self.failIf(hasattr(request.response, 'a'))
+            request.response.body = 'OK'
+            return request.response
+        environ = self._makeEnviron()
+        self._registerView(view, '', IViewClassifier, IRequest, IContext)
+        self._registerView(exc_view, '', IExceptionViewClassifier,
+                           IRequest, KeyError)
+        router = self._makeOne()
+        start_response = DummyStartResponse()
+        itera = router(environ, start_response)
+        self.assertEqual(itera, ['OK'])
+
     def test_call_request_has_response_callbacks(self):
         from zope.interface import Interface
         from zope.interface import directlyProvides