Merge "Fix issubclass() hook behavior in PluginInterface"

neutron/api/extensions.py

@@ -51,6 +51,10 @@ class PluginInterface(object):
         marked with the abstractmethod decorator is
         provided by the plugin class.
         """
+
+        if not cls.__abstractmethods__:
+            return NotImplemented
+
         for method in cls.__abstractmethods__:
             if any(method in base.__dict__ for base in klass.__mro__):
                 continue

neutron/tests/unit/test_extensions.py

@@ -15,6 +15,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import abc
+
 import mock
 import routes
 import webob
@@ -57,6 +59,47 @@ class FakePluginWithExtension(db_base_plugin_v2.NeutronDbPluginV2):
         self._log("method_to_support_foxnsox_extension", context)
 
 
+class PluginInterfaceTest(base.BaseTestCase):
+    def test_issubclass_hook(self):
+        class A(object):
+            def f(self):
+                pass
+
+        class B(extensions.PluginInterface):
+            @abc.abstractmethod
+            def f(self):
+                pass
+
+        self.assertTrue(issubclass(A, B))
+
+    def test_issubclass_hook_class_without_abstract_methods(self):
+        class A(object):
+            def f(self):
+                pass
+
+        class B(extensions.PluginInterface):
+            def f(self):
+                pass
+
+        self.assertFalse(issubclass(A, B))
+
+    def test_issubclass_hook_not_all_methods_implemented(self):
+        class A(object):
+            def f(self):
+                pass
+
+        class B(extensions.PluginInterface):
+            @abc.abstractmethod
+            def f(self):
+                pass
+
+            @abc.abstractmethod
+            def g(self):
+                pass
+
+        self.assertFalse(issubclass(A, B))
+
+
 class ResourceExtensionTest(base.BaseTestCase):
 
     class ResourceExtensionController(wsgi.Controller):