basic ExtensionManager implementation

setup.py

@@ -57,7 +57,12 @@ setup(
     #                                only_in_packages=False,
     #                                ),
 
-    entry_points={},
+    entry_points={
+        'stevedore.test.extension': [
+            't1 = stevedore.tests.test_extension:FauxExtension',
+            't2 = stevedore.tests.test_extension:FauxExtension',
+            ],
+        },
 
     zip_safe=False,
     )

stevedore/extension.py

@@ -0,0 +1,43 @@
+"""ExtensionManager
+"""
+
+import pkg_resources
+
+import logging
+
+
+LOG = logging.getLogger(__name__)
+
+
+class Extension(object):
+
+    def __init__(self, name, entry_point, plugin, obj):
+        self.name = name
+        self.entry_point = entry_point
+        self.plugin = plugin
+        self.obj = obj
+
+
+class ExtensionManager(object):
+
+    def __init__(self, namespace, invoke_on_load=False, invoke_args=(), invoke_kwds={}):
+        self.namespace = namespace
+        self.extensions = []
+        for ep in pkg_resources.iter_entry_points(self.namespace):
+            LOG.debug('found extension %r', ep.name)
+            try:
+                plugin = ep.load()
+                if invoke_on_load:
+                    obj = plugin(ep.name, *invoke_args, **invoke_kwds)
+                else:
+                    obj = None
+            except KeyboardInterrupt:
+                raise
+            except Exception as err:
+                LOG.error('Could not load %s: %s', ep.name, err)
+            else:
+                self.extensions.append(Extension(ep.name, ep, plugin, obj))
+        return
+
+    def names(self):
+        return [e.name for e in self.extensions]

stevedore/tests/test_extension.py

@@ -0,0 +1,29 @@
+"""Tests for stevedore.extension
+"""
+
+from stevedore import extension
+
+
+class FauxExtension(object):
+    def __init__(self, name, *args, **kwds):
+        self.name = name
+        self.args = args
+        self.kwds = kwds
+
+
+def test_detect_plugins():
+    em = extension.ExtensionManager('stevedore.test.extension')
+    names = sorted(em.names())
+    assert names == ['t1', 't2']
+
+
+def test_invoke_on_load():
+    em = extension.ExtensionManager('stevedore.test.extension',
+                                    invoke_on_load=True,
+                                    invoke_args=('a',),
+                                    invoke_kwds={'b': 'B'},
+                                    )
+    assert len(em.extensions) == 2
+    for e in em.extensions:
+        assert e.obj.args == ('a',)
+        assert e.obj.kwds == {'b': 'B'}