Resolves Issue #590

CHANGELOG.md

@@ -4,8 +4,10 @@
 
 Bugs:
 
-- `[ext.argparse]` Parse (`self._parser`) not accessible inside `_pre_argument_parsing`
-
+- `[ext.argparse]` Parser (`self._parser`) not accessible inside `_pre_argument_parsing` when `stacked_type = 'embedded'`
+    - [Issue #569](https://github.com/datafolklabs/cement/issues/569)
+- `[ext.configparser]` Overriding config options with environment variables doesn't work correctly with surrounding underscore characters 
+    - [Issue #590](https://github.com/datafolklabs/cement/issues/590)
 
 Features:
 

cement/ext/ext_configparser.py

@@ -149,11 +149,12 @@ def _get_env_var(self, section, key):
                 self.app._meta.config_section, section, key)
 
         env_var = env_var.upper()
-        env_var = re.sub('[^0-9a-zA-Z]+', '_', env_var)
+        env_var = re.sub('[^0-9a-zA-Z_]+', '_', env_var)
         return env_var
 
     def get(self, section, key, **kwargs):
         env_var = self._get_env_var(section, key)
+
         if env_var in os.environ.keys():
             return os.environ[env_var]
         else:

tests/ext/test_ext_configparser.py

@@ -55,6 +55,16 @@ def test_env_var_override():
         section_dict = app.config.get_section_dict('dummy')
         assert section_dict['foo'] == 'dummy-not-bar'
 
+        # issue/590 - don't sub underscores
+
+        app.config.set('testapp', '__foo__', 'bar')
+        env_var = "TESTAPP___FOO__"
+
+        os.environ[env_var] = 'not-bar'
+        assert app.config.get('testapp', '__foo__') == 'not-bar'
+        section_dict = app.config.get_section_dict('testapp')
+        assert section_dict['__foo__'] == 'not-bar'
+
 
 def test_get_boolean():
     with TestApp(config_section='testapp') as app: