add hook manager

stevedore/hook.py

@@ -0,0 +1,16 @@
+from .named import NamedExtensionManager
+
+
+class HookManager(NamedExtensionManager):
+    """Coordinate execution of extensions using a shared name.
+    """
+
+    def __init__(self, namespace, name,
+                 invoke_on_load=False, invoke_args=(), invoke_kwds={}):
+        super(HookManager, self).__init__(
+            namespace,
+            [name],
+            invoke_on_load=invoke_on_load,
+            invoke_args=invoke_args,
+            invoke_kwds=invoke_kwds,
+            )

stevedore/named.py

@@ -8,7 +8,7 @@ class NamedExtensionManager(EnabledExtensionManager):
     configuration file, for example.
     """
 
-    def __init__(self, namespace, names=[],
+    def __init__(self, namespace, names,
                  invoke_on_load=False, invoke_args=(), invoke_kwds={}):
         def check(ep):
             return ep.name in names

stevedore/tests/test_hook.py

@@ -0,0 +1,13 @@
+from stevedore import hook
+
+
+def test_hook():
+    em = hook.HookManager(
+        'stevedore.test.extension',
+        't1',
+        invoke_on_load=True,
+        invoke_args=('a',),
+        invoke_kwds={'b': 'B'},
+        )
+    assert len(em.extensions) == 1
+    assert em.names() == ['t1']