Resolve UnboundLocalError

As discussed in bug 1841038, configuring a StrOpt with a regex parameter
and providing an invalid environment variable will result in an ugly
stacktrace due to an undefined 'alt_loc' variable. Resolve this by
creating said variable.

Change-Id: Id0fb6efdc435a2bd88d5dfea2b4720df453fbfec
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>
Closes-Bug: #1841038

oslo_config/cfg.py

@@ -2678,6 +2678,7 @@ class ConfigOpts(abc.Mapping):
             namespace = self._namespace
         if namespace is not None:
             try:
+                alt_loc = None
                 try:
                     val, alt_loc = opt._get_from_namespace(namespace,
                                                            group_name)
@@ -2692,6 +2693,10 @@ class ConfigOpts(abc.Mapping):
                     if val != sources._NoValue:
                         return (convert(val), alt_loc)
                 except KeyError:  # nosec: Valid control flow instruction
+                    alt_loc = LocationInfo(
+                        Locations.environment,
+                        self._env_driver.get_name(group_name, name),
+                    )
                     # If there was a KeyError looking at config files or
                     # command line, retry the env_val.
                     if env_val[0] != sources._NoValue:

oslo_config/sources/_environment.py

@@ -77,12 +77,19 @@ class EnvironmentConfigurationSource(sources.ConfigurationSource):
     """A configuration source for options in the environment."""
 
     @staticmethod
-    def _make_name(group_name, option_name):
+    def get_name(group_name, option_name):
+        """Return the expected environment variable name for the given option.
+
+        :param group_name: The group name or None. Defaults to 'DEFAULT' if
+            None.
+        :param option_name: The option name.
+        :returns: Th expected environment variable name.
+        """
         group_name = group_name or 'DEFAULT'
         return 'OS_{}__{}'.format(group_name.upper(), option_name.upper())
 
     def get(self, group_name, option_name, opt):
-        env_name = self._make_name(group_name, option_name)
+        env_name = self.get_name(group_name, option_name)
         try:
             value = os.environ[env_name]
             loc = oslo_config.cfg.LocationInfo(

oslo_config/tests/test_sources.py

@@ -15,6 +15,7 @@ import os
 from oslotest import base
 from requests import HTTPError
 import requests_mock
+import testtools
 
 from oslo_config import _list_opts
 from oslo_config import cfg
@@ -120,10 +121,13 @@ class TestEnvironmentConfigurationSource(base.BaseTestCase):
         self.conf = cfg.ConfigOpts()
         self.conf_fixture = self.useFixture(fixture.Config(self.conf))
         self.conf.register_opt(cfg.StrOpt('bar'), 'foo')
+        self.conf.register_opt(cfg.StrOpt('baz', regex='^[a-z].*$'), 'foo')
 
         def cleanup():
-            if 'OS_FOO__BAR' in os.environ:
-                del os.environ['OS_FOO__BAR']
+            for env in ('OS_FOO__BAR', 'OS_FOO__BAZ'):
+                if env in os.environ:
+                    del os.environ[env]
+
         self.addCleanup(cleanup)
 
     def test_simple_environment_get(self):
@@ -171,6 +175,14 @@ class TestEnvironmentConfigurationSource(base.BaseTestCase):
         self.conf(args=[], use_env=True)
         self.assertEqual(env_value, self.conf['foo']['bar'])
 
+    def test_invalid_env(self):
+        self.conf(args=[])
+        env_value = 'ABC'
+        os.environ['OS_FOO__BAZ'] = env_value
+
+        with testtools.ExpectedException(cfg.ConfigSourceValueError):
+            self.conf['foo']['baz']
+
 
 def make_uri(name):
     return "https://oslo.config/{}.conf".format(name)