From bb5d643b83cde30d2fa37aaae21a8d4b225f584b Mon Sep 17 00:00:00 2001
From: Chris McDonough <chrism@agendaless.com>
Date: Sun, 20 Jul 2008 03:04:58 +0000
Subject:   - Add find_interface API.

---
 CHANGES.txt                        |  4 ++++
 docs/api/traversal.rst             | 10 ++++++++++
 docs/index.rst                     |  1 +
 repoze/bfg/tests/test_traversal.py | 28 ++++++++++++++++++++++++++++
 repoze/bfg/traversal.py            |  8 ++++++++
 5 files changed, 51 insertions(+)
 create mode 100644 docs/api/traversal.rst

diff --git a/CHANGES.txt b/CHANGES.txt
index d94b25e99..f1945e814 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,3 +1,7 @@
+After 0.2
+
+  - Add find_interface API.
+
 0.2
 
   - Add wsgiapp decorator.
diff --git a/docs/api/traversal.rst b/docs/api/traversal.rst
new file mode 100644
index 000000000..56dad2290
--- /dev/null
+++ b/docs/api/traversal.rst
@@ -0,0 +1,10 @@
+.. _traversal_module:
+
+:mod:`repoze.bfg.traversal`
+---------------------------
+
+.. currentmodule:: repoze.bfg.traversal
+
+.. autofunction:: find_interface
+
+
diff --git a/docs/index.rst b/docs/index.rst
index ceb2e5fd9..28b2d91d4 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -35,6 +35,7 @@ and run a web application.
    api/router
    api/security
    api/template
+   api/traversal
    api/wsgi
 
 Indices and tables
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
-- 
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