Allow providing a default value to CLI loading

Allow users to specify a default value to loading auth plugins from the
CLI so that you can fallback to some default behaviour if the user
doesn't specify a plugin.

Change-Id: I44eb838f7ccc3b377dd1ba53dbb941e973e4a22e

2 files changed, 55 insertions, 8 deletions

diff --git a/keystoneclient/auth/cli.py b/keystoneclient/auth/cli.py
index 8bbed2a..f1f2de3 100644
--- a/keystoneclient/auth/cli.py
+++ b/keystoneclient/auth/cli.py
@@ -14,9 +14,11 @@ import argparse
 import os
 
 from keystoneclient.auth import base
+from keystoneclient import utils
 
 
-def register_argparse_arguments(parser, argv):
+@utils.positional()
+def register_argparse_arguments(parser, argv, default=None):
     """Register CLI options needed to create a plugin.
 
     The function inspects the provided arguments so that it can also register
@@ -24,13 +26,15 @@ def register_argparse_arguments(parser, argv):
 
     :param argparse.ArgumentParser: the parser to attach argparse options to.
     :param list argv: the arguments provided to the appliation.
+    :param str/class default: a default plugin name or a plugin object to use
+                              if one isn't specified by the CLI. default: None.
 
     :returns: The plugin class that will be loaded or None if not provided.
 
     :raises exceptions.NoMatchingPlugin: if a plugin cannot be created.
     """
     in_parser = argparse.ArgumentParser(add_help=False)
-    env_plugin = os.environ.get('OS_AUTH_PLUGIN')
+    env_plugin = os.environ.get('OS_AUTH_PLUGIN', default)
     for p in (in_parser, parser):
         p.add_argument('--os-auth-plugin',
                        metavar='<name>',
@@ -38,15 +42,18 @@ def register_argparse_arguments(parser, argv):
                        help='The auth plugin to load')
 
     options, _args = in_parser.parse_known_args(argv)
-    name = options.os_auth_plugin
 
-    if not name:
+    if not options.os_auth_plugin:
         return None
 
-    msg = 'Options specific to the %s plugin.' % name
-    group = parser.add_argument_group('Authentication Options', msg)
+    if isinstance(options.os_auth_plugin, type):
+        msg = 'Default Authentication options'
+        plugin = options.os_auth_plugin
+    else:
+        msg = 'Options specific to the %s plugin.' % options.os_auth_plugin
+        plugin = base.get_plugin_class(options.os_auth_plugin)
 
-    plugin = base.get_plugin_class(name)
+    group = parser.add_argument_group('Authentication Options', msg)
     plugin.register_argparse_arguments(group)
     return plugin
 
@@ -66,5 +73,9 @@ def load_from_argparse_arguments(namespace, **kwargs):
     if not namespace.os_auth_plugin:
         return None
 
-    plugin = base.get_plugin_class(namespace.os_auth_plugin)
+    if isinstance(namespace.os_auth_plugin, type):
+        plugin = namespace.os_auth_plugin
+    else:
+        plugin = base.get_plugin_class(namespace.os_auth_plugin)
+
     return plugin.load_from_argparse_arguments(namespace, **kwargs)
diff --git a/keystoneclient/tests/auth/test_cli.py b/keystoneclient/tests/auth/test_cli.py
index 4d3289e..fc09195 100644
--- a/keystoneclient/tests/auth/test_cli.py
+++ b/keystoneclient/tests/auth/test_cli.py
@@ -104,6 +104,42 @@ class CliTests(utils.TestCase):
         self.assertEqual(self.a_float, a['a_float'])
         self.assertEqual(3, a['a_int'])
 
+    @utils.mock_plugin
+    def test_with_default_string_value(self, m):
+        name = uuid.uuid4().hex
+        klass = cli.register_argparse_arguments(self.p, [], default=name)
+        self.assertIs(utils.MockPlugin, klass)
+        m.assert_called_once_with(name)
+
+    @utils.mock_plugin
+    def test_overrides_default_string_value(self, m):
+        name = uuid.uuid4().hex
+        default = uuid.uuid4().hex
+        argv = ['--os-auth-plugin', name]
+        klass = cli.register_argparse_arguments(self.p, argv, default=default)
+        self.assertIs(utils.MockPlugin, klass)
+        m.assert_called_once_with(name)
+
+    @utils.mock_plugin
+    def test_with_default_type_value(self, m):
+        klass = cli.register_argparse_arguments(self.p, [],
+                                                default=utils.MockPlugin)
+        self.assertIs(utils.MockPlugin, klass)
+        self.assertEqual(0, m.call_count)
+
+    @utils.mock_plugin
+    def test_overrides_default_type_value(self, m):
+        # using this test plugin would fail if called because there
+        # is no get_options() function
+        class TestPlugin(object):
+            pass
+        name = uuid.uuid4().hex
+        argv = ['--os-auth-plugin', name]
+        klass = cli.register_argparse_arguments(self.p, argv,
+                                                default=TestPlugin)
+        self.assertIs(utils.MockPlugin, klass)
+        m.assert_called_once_with(name)
+
     def test_deprecated_cli_options(self):
         TesterPlugin.register_argparse_arguments(self.p)
         val = uuid.uuid4().hex