- A new internal exception class (*not* an API) named

  ``repoze.bfg.exceptions.PredicateMismatch`` now exists.  This
  exception is currently raised when no constituent view of a
  multiview can be called (due to no predicate match).  Previously, in
  this situation, a ``repoze.bfg.exceptions.NotFound`` was raised.  We
  provide backwards compatibility for code that expected a
  ``NotFound`` to be raised when no predicates match by causing
  ``repoze.bfg.exceptions.PredicateMismatch`` to inherit from
  ``NotFound``.  This will cause any exception view registered for
  ``NotFound`` to be called when a predicate mismatch occurs, as was
  the previous behavior.

  There is however, one perverse case that will expose a backwards
  incompatibility.  If 1) you had a view that was registered as a
  member of a multiview 2) this view explicitly raised a ``NotFound``
  exception *in order to* proceed to the next predicate check in the
  multiview, that code will now behave differently: rather than
  skipping to the next view match, a NotFound will be raised to the
  top-level exception handling machinery instead.  For code to be
  depending upon the behavior of a view raising ``NotFound`` to
  proceed to the next predicate match, would be tragic, but not
  impossible, given that ``NotFound`` is a public interface.
  ``repoze.bfg.exceptions.PredicateMismatch`` is not a public API and
  cannot be depended upon by application code, so you should not
  change your view code to raise ``PredicateMismatch``.  Instead, move
  the logic which raised the ``NotFound`` exception in the view out
  into a custom view predicate.

1 files changed, 15 insertions, 2 deletions

diff --git a/repoze/bfg/tests/test_configuration.py b/repoze/bfg/tests/test_configuration.py
index 4df7af1c2..17708bf63 100644
--- a/repoze/bfg/tests/test_configuration.py
+++ b/repoze/bfg/tests/test_configuration.py
@@ -3307,20 +3307,33 @@ class TestMultiView(unittest.TestCase):
         self.assertRaises(NotFound, mv, context, request)
 
     def test___call__intermediate_not_found(self):
-        from repoze.bfg.exceptions import NotFound
+        from repoze.bfg.exceptions import PredicateMismatch
         mv = self._makeOne()
         context = DummyContext()
         request = DummyRequest()
         request.view_name = ''
         expected_response = DummyResponse()
         def view1(context, request):
-            raise NotFound
+            raise PredicateMismatch
         def view2(context, request):
             return expected_response
         mv.views = [(100, view1, None), (99, view2, None)]
         response = mv(context, request)
         self.assertEqual(response, expected_response)
 
+    def test___call__raise_not_found_isnt_interpreted_as_pred_mismatch(self):
+        from repoze.bfg.exceptions import NotFound
+        mv = self._makeOne()
+        context = DummyContext()
+        request = DummyRequest()
+        request.view_name = ''
+        def view1(context, request):
+            raise NotFound
+        def view2(context, request):
+            """ """
+        mv.views = [(100, view1, None), (99, view2, None)]
+        self.assertRaises(NotFound, mv, context, request)
+
     def test___call__(self):
         mv = self._makeOne()
         context = DummyContext()