- Add find_interface API.

2 files changed, 36 insertions, 0 deletions

diff --git a/repoze/bfg/tests/test_traversal.py b/repoze/bfg/tests/test_traversal.py
index 61dff6d88..2cd02da5e 100644
--- a/repoze/bfg/tests/test_traversal.py
+++ b/repoze/bfg/tests/test_traversal.py
@@ -130,6 +130,34 @@ class NaivePublishTraverserTests(unittest.TestCase, PlacelessSetup):
         self.assertEqual(ctx.__parent__.__parent__.__parent__.__name__, None)
         self.assertEqual(ctx.__parent__.__parent__.__parent__.__parent__, None)
 
+class FindInterfaceTests(unittest.TestCase):
+    def _getFUT(self):
+        from repoze.bfg.traversal import find_interface
+        return find_interface
+
+    def test_it(self):
+        baz = DummyContext()
+        bar = DummyContext(baz)
+        foo = DummyContext(bar)
+        root = DummyContext(foo)
+        root.__parent__ = None
+        root.__name__ = 'root'
+        foo.__parent__ = root
+        foo.__name__ = 'foo'
+        bar.__parent__ = foo
+        bar.__name__ = 'bar'
+        baz.__parent__ = bar
+        baz.__name__ = 'baz'
+        request = DummyRequest()
+        from zope.interface import directlyProvides
+        from zope.interface import Interface
+        class IFoo(Interface):
+            pass
+        directlyProvides(root, IFoo)
+        finder = self._getFUT()
+        result = finder(baz, IFoo)
+        self.assertEqual(result.__name__, 'root')
+
 class DummyContext(object):
     def __init__(self, next=None):
         self.next = next
diff --git a/repoze/bfg/traversal.py b/repoze/bfg/traversal.py
index a9f127841..ee66ae887 100644
--- a/repoze/bfg/traversal.py
+++ b/repoze/bfg/traversal.py
@@ -3,6 +3,7 @@ import urllib
 from zope.interface import classProvides
 from zope.interface import implements
 from zope.location.location import located
+from zope.location.location import LocationIterator
 from zope.location.interfaces import ILocation
 
 from repoze.bfg.interfaces import ITraverser
@@ -63,3 +64,10 @@ class NaiveTraverser(object):
 
         return ob, name, path
 
+def find_interface(context, interface):
+    """ Return an object providing 'interface' anywhere in the parent
+    chain of 'context' or None if no object providing that interface
+    can be found in the parent chain """
+    for location in LocationIterator(context):
+        if interface.providedBy(location):
+            return location