Make predicate mismatches not hide other possible valid views.

This is mostly an issue for REST style views that use request_method
predicates and are registered for context interfaces.

See Issue #409

2 files changed, 92 insertions, 2 deletions

diff --git a/pyramid/router.py b/pyramid/router.py
index 9b6138ea9..bb2466ec3 100644
--- a/pyramid/router.py
+++ b/pyramid/router.py
@@ -1,4 +1,5 @@
 from zope.interface import (
+    Interface,
     implementer,
     providedBy,
     )
@@ -24,6 +25,7 @@ from pyramid.events import (
     NewResponse,
     )
 
+from pyramid.exceptions import PredicateMismatch
 from pyramid.httpexceptions import HTTPNotFound
 from pyramid.request import Request
 from pyramid.threadlocal import manager
@@ -158,8 +160,24 @@ class Router(object):
                 msg = request.path_info
             raise HTTPNotFound(msg)
         else:
-            response = view_callable(context, request)
-
+            try:
+                response = view_callable(context, request)
+            except PredicateMismatch:
+                # look for other views that meet the predicate
+                # criteria
+                for iface in [i for i in context_iface.flattened()
+                              if i != Interface]:
+                    view_callable = adapters.lookup(
+                        (IViewClassifier, request.request_iface, iface),
+                        IView, name=view_name, default=None)
+                    if view_callable is not None:
+                        try:
+                            response = view_callable(context, request)
+                            break
+                        except PredicateMismatch:
+                            pass
+                else:
+                    raise
         return response
 
     def invoke_subrequest(self, request, use_tweens=False):
diff --git a/pyramid/tests/test_router.py b/pyramid/tests/test_router.py
index 65152ca05..32e74a3b3 100644
--- a/pyramid/tests/test_router.py
+++ b/pyramid/tests/test_router.py
@@ -1164,6 +1164,78 @@ class TestRouter(unittest.TestCase):
         start_response = DummyStartResponse()
         self.assertRaises(RuntimeError, router, environ, start_response)
 
+    def test_call_view_raises_predicate_mismatch(self):
+        from pyramid.exceptions import PredicateMismatch
+        from pyramid.interfaces import IViewClassifier
+        from pyramid.interfaces import IRequest
+        view = DummyView(DummyResponse(), raise_exception=PredicateMismatch)
+        self._registerView(view, '', IViewClassifier, IRequest, None)
+        environ = self._makeEnviron()
+        router = self._makeOne()
+        start_response = DummyStartResponse()
+        self.assertRaises(PredicateMismatch, router, environ, start_response)
+
+    def test_call_view_predicate_mismatch_doesnt_hide_views(self):
+        from pyramid.exceptions import PredicateMismatch
+        from pyramid.interfaces import IViewClassifier
+        from pyramid.interfaces import IRequest, IResponse
+        from pyramid.response import Response
+        from zope.interface import Interface, implementer
+        class IContext(Interface):
+            pass
+        @implementer(IContext)
+        class DummyContext:
+            pass
+        context = DummyContext()
+        self._registerTraverserFactory(context)
+        view = DummyView(DummyResponse(), raise_exception=PredicateMismatch)
+        self._registerView(view, '', IViewClassifier, IRequest,
+                           DummyContext)
+        good_view = DummyView('abc')
+        self._registerView(self.config.derive_view(good_view),
+                            '', IViewClassifier, IRequest, IContext)
+        router = self._makeOne()
+        def make_response(s):
+            return Response(s)
+        router.registry.registerAdapter(make_response, (str,), IResponse)
+        environ = self._makeEnviron()
+        start_response = DummyStartResponse()
+        app_iter = router(environ, start_response)
+        self.assertEqual(app_iter, [b'abc'])
+
+    def test_call_view_multiple_predicate_mismatches_dont_hide_views(self):
+        from pyramid.exceptions import PredicateMismatch
+        from pyramid.interfaces import IViewClassifier
+        from pyramid.interfaces import IRequest, IResponse
+        from pyramid.response import Response
+        from zope.interface import Interface, implementer
+        class IBaseContext(Interface):
+            pass
+        class IContext(IBaseContext):
+            pass
+        @implementer(IContext)
+        class DummyContext:
+            pass
+        context = DummyContext()
+        self._registerTraverserFactory(context)
+        view1 = DummyView(DummyResponse(), raise_exception=PredicateMismatch)
+        self._registerView(view1, '', IViewClassifier, IRequest,
+                           DummyContext)
+        view2 = DummyView(DummyResponse(), raise_exception=PredicateMismatch)
+        self._registerView(view2, '', IViewClassifier, IRequest,
+                           IContext)
+        good_view = DummyView('abc')
+        self._registerView(self.config.derive_view(good_view),
+                            '', IViewClassifier, IRequest, IBaseContext)
+        router = self._makeOne()
+        def make_response(s):
+            return Response(s)
+        router.registry.registerAdapter(make_response, (str,), IResponse)
+        environ = self._makeEnviron()
+        start_response = DummyStartResponse()
+        app_iter = router(environ, start_response)
+        self.assertEqual(app_iter, [b'abc'])
+
 class DummyPredicate(object):
     def __call__(self, info, request):
         return True