Allow arbitrary client-specific options

There are occasionally some client-specific things that would be handy
to be able to configure about behaviors. For instance, the only config
file that ansible's openstack inventory has is clouds.yaml. Rather than
teaching os-client-config about such things, allow a pass-through config
section. Apply key normalization to _'s like other configs, and merge
the clouds and secure files so that the sections behave like other OCC
config sections.

Change-Id: If307e95006abf6e1efbbd77cfc99e5fdfed6c80a

os_client_config/config.py

@@ -253,6 +253,19 @@ class OpenStackConfig(object):
         # Flag location to hold the peeked value of an argparse timeout value
         self._argv_timeout = False
 
+    def get_extra_config(self, key, defaults=None):
+        """Fetch an arbitrary extra chunk of config, laying in defaults.
+
+        :param string key: name of the config section to fetch
+        :param dict defaults: (optional) default values to merge under the
+                                         found config
+        """
+        if not defaults:
+            defaults = {}
+        return _merge_clouds(
+            self._normalize_keys(defaults),
+            self._normalize_keys(self.cloud_config.get(key, {})))
+
     def _load_config_file(self):
         return self._load_yaml_json_file(self._config_files)
 

os_client_config/tests/base.py

@@ -121,6 +121,10 @@ USER_CONF = {
             'region_name': 'test-region',
         }
     },
+    'ansible': {
+        'expand-hostvars': False,
+        'use_hostnames': True,
+    },
 }
 SECURE_CONF = {
     'clouds': {

os_client_config/tests/test_config.py

@@ -372,6 +372,27 @@ class TestConfigArgparse(base.TestCase):
 
         self.assertDictEqual({'compute_api_version': 1}, fixed_args)
 
+    def test_extra_config(self):
+        c = config.OpenStackConfig(config_files=[self.cloud_yaml],
+                                   vendor_files=[self.vendor_yaml])
+
+        defaults = {'use_hostnames': False, 'other-value': 'something'}
+        ansible_options = c.get_extra_config('ansible', defaults)
+
+        # This should show that the default for use_hostnames above is
+        # overridden by the value in the config file defined in base.py
+        # It should also show that other-value key is normalized and passed
+        # through even though there is no corresponding value in the config
+        # file, and that expand-hostvars key is normalized and the value
+        # from the config comes through even though there is no default.
+        self.assertDictEqual(
+            {
+                'expand_hostvars': False,
+                'use_hostnames': True,
+                'other_value': 'something',
+            },
+            ansible_options)
+
     def test_register_argparse_cloud(self):
         c = config.OpenStackConfig(config_files=[self.cloud_yaml],
                                    vendor_files=[self.vendor_yaml])