Provide a means to get all installed plugins

Particular for use in writing error messages and help text it can be
useful to get a list of all the plugins that are installed on the
system. Provide a version that returns the classes as well so that you
don't have to reload the modules if the user is picking one.

Closes-Bug: #1423711
Change-Id: I021249eac8156c2d3ccbbacb7503184b6eb6e784

keystoneclient/auth/__init__.py

@@ -20,6 +20,8 @@ __all__ = [
     # auth.base
     'AUTH_INTERFACE',
     'BaseAuthPlugin',
+    'get_available_plugin_names',
+    'get_available_plugin_classes',
     'get_plugin_class',
     'IDENTITY_AUTH_HEADER_NAME',
     'PLUGIN_NAMESPACE',

keystoneclient/auth/base.py

@@ -27,6 +27,34 @@ PLUGIN_NAMESPACE = 'keystoneclient.auth.plugin'
 IDENTITY_AUTH_HEADER_NAME = 'X-Auth-Token'
 
 
+def get_available_plugin_names():
+    """Get the names of all the plugins that are available on the system.
+
+    This is particularly useful for help and error text to prompt a user for
+    example what plugins they may specify.
+
+    :returns: A list of names.
+    :rtype: frozenset
+    """
+    mgr = stevedore.ExtensionManager(namespace=PLUGIN_NAMESPACE,
+                                     invoke_on_load=False)
+    return frozenset(mgr.names())
+
+
+def get_available_plugin_classes():
+    """Retrieve all the plugin classes available on the system.
+
+    :returns: A dict with plugin entrypoint name as the key and the plugin
+              class as the value.
+    :rtype: dict
+    """
+    mgr = stevedore.ExtensionManager(namespace=PLUGIN_NAMESPACE,
+                                     propagate_map_exceptions=True,
+                                     invoke_on_load=False)
+
+    return dict(mgr.map(lambda ext: (ext.entry_point.name, ext.plugin)))
+
+
 def get_plugin_class(name):
     """Retrieve a plugin class by its entrypoint name.
 

keystoneclient/tests/unit/auth/test_auth.py

@@ -0,0 +1,36 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from keystoneclient import auth
+from keystoneclient.auth import identity
+from keystoneclient.tests.unit.auth import utils
+
+
+class AuthTests(utils.TestCase):
+
+    def test_plugin_names_in_available(self):
+        plugins = auth.get_available_plugin_names()
+
+        for p in ('password', 'v2password', 'v3password',
+                  'token', 'v2token', 'v3token'):
+            self.assertIn(p, plugins)
+
+    def test_plugin_classes_in_available(self):
+        plugins = auth.get_available_plugin_classes()
+
+        self.assertIs(plugins['password'], identity.Password)
+        self.assertIs(plugins['v2password'], identity.V2Password)
+        self.assertIs(plugins['v3password'], identity.V3Password)
+
+        self.assertIs(plugins['token'], identity.Token)
+        self.assertIs(plugins['v2token'], identity.V2Token)
+        self.assertIs(plugins['v3token'], identity.V3Token)