Load only predefined variables by default

README.rst

@@ -86,6 +86,12 @@ ENV_PREFIX
   The prefix will be removed from the environment variable name when setting in the configuration.
   (default: :code:`''`, example: :code:`ENV_PREFIX = 'MYAPP_'`)
 
+ENV_LOAD_ALL
+  Whether or not to load all environment variables for the configuration object.
+  When :code:`False` only settings predefined on the configuration object are loaded, all others are ignored.
+  When :code:`True` all environment variables defined in :code:`os.environ` will get loaded into your configuration object.
+  (default :code:`False`)
+
 
 Setting configuration values
 ----------------------------
@@ -99,3 +105,4 @@ You can set the :code:`flask-env` configuration settings directly on your Flask
 
    class Configuration(metaclass=MetaFlaskEnv):
        ENV_PREFIX = 'MYAPP_'
+       ENV_LOAD_ALL = False

flask_env.py

@@ -13,6 +13,7 @@ class MetaFlaskEnv(type):
 
         # Get our internal settings
         prefix = dict.get('ENV_PREFIX', '')
+        load_all = dict.get('ENV_LOAD_ALL', False)
 
         # Override default configuration from environment variables
         for key, value in os.environ.items():
@@ -23,6 +24,11 @@ class MetaFlaskEnv(type):
             # Strip the prefix from the environment variable name
             key = key[len(prefix):]
 
+            # Unless we specify that we want to load all environment variables
+            #   only load variables that we have predefined on our object
+            if not load_all and not hasattr(cls, key):
+                continue
+
             # If value is "true" or "false", parse as a boolean
             # Otherwise, if it contains a "." then try to parse as a float
             # Otherwise, try to parse as an integer

test_flask_env.py

@@ -5,16 +5,17 @@ from flask_env import MetaFlaskEnv
 
 
 class TestFlaskEnv(unittest.TestCase):
-    def _get_test_configuration(self, env_prefix=''):
+    def _get_test_configuration(self, env_prefix='', env_load_all=False, **kwargs):
         """Helper to define a new configuration class using our MetaFlaskEnv"""
         return MetaFlaskEnv('TestConfiguration', (object, ), dict(
             ENV_PREFIX=env_prefix,
-            DEFAULT_SETTING='default_value',
+            ENV_LOAD_ALL=env_load_all,
+            **kwargs
         ))
 
     def test_default_settings(self):
         """A test to ensure that if no environment variable is set, we get the default value that is set"""
-        TestConfiguration = self._get_test_configuration()
+        TestConfiguration = self._get_test_configuration(DEFAULT_SETTING='default_value')
         self.assertEqual(TestConfiguration.DEFAULT_SETTING, 'default_value')
 
     def test_override_from_env(self):
@@ -22,7 +23,7 @@ class TestFlaskEnv(unittest.TestCase):
         # DEV: We have to set the environment variable first, since they get loaded into the class on definition
         os.environ['DEFAULT_SETTING'] = 'set_by_env'
 
-        TestConfiguration = self._get_test_configuration()
+        TestConfiguration = self._get_test_configuration(DEFAULT_SETTING='default_value')
         self.assertEqual(TestConfiguration.DEFAULT_SETTING, 'set_by_env')
 
     def test_only_set_on_env(self):
@@ -30,15 +31,20 @@ class TestFlaskEnv(unittest.TestCase):
         # DEV: We have to set the environment variable first, since they get loaded into the class on definition
         os.environ['NEW_SETTING'] = 'set_by_env'
 
-        TestConfiguration = self._get_test_configuration()
+        # When configured to load all environment variables
+        TestConfiguration = self._get_test_configuration(env_load_all=True)
         self.assertEqual(TestConfiguration.NEW_SETTING, 'set_by_env')
 
+        # When configured to not load all environment variables
+        TestConfiguration = self._get_test_configuration(env_load_all=False)
+        self.assertFalse(hasattr(TestConfiguration, 'NEW_SETTING'))
+
     def test_env_prefix(self):
         """A test to ensure that the ENV_PREFIX setting functions as needed"""
         # DEV: We have to set the environment variable first, since they get loaded into the class on definition
         os.environ['TEST_DEFAULT_SETTING'] = 'set_by_env'
 
-        TestConfiguration = self._get_test_configuration(env_prefix='TEST_')
+        TestConfiguration = self._get_test_configuration(env_prefix='TEST_', DEFAULT_SETTING='default_value')
         self.assertEqual(TestConfiguration.DEFAULT_SETTING, 'set_by_env')
 
     def test_env_prefix_non_matching(self):
@@ -46,7 +52,7 @@ class TestFlaskEnv(unittest.TestCase):
         # DEV: We have to set the environment variable first, since they get loaded into the class on definition
         os.environ['DEFAULT_SETTING'] = 'set_by_env'
 
-        TestConfiguration = self._get_test_configuration(env_prefix='MYAPP_')
+        TestConfiguration = self._get_test_configuration(env_prefix='MYAPP_', DEFAULT_SETTING='default_value')
         self.assertEqual(TestConfiguration.DEFAULT_SETTING, 'default_value')
 
     def test_parsing_boolean(self):
@@ -57,7 +63,8 @@ class TestFlaskEnv(unittest.TestCase):
         os.environ['IS_FALSE'] = 'FALSE'
         os.environ['IS_WACKY_FALSE'] = 'FaLSe'
 
-        TestConfiguration = self._get_test_configuration()
+        # DEV: Set `env_load_all=True` to keep from having to make default values for each variable
+        TestConfiguration = self._get_test_configuration(env_load_all=True)
         self.assertEqual(TestConfiguration.IS_TRUE, True)
         self.assertEqual(TestConfiguration.IS_NOT_TRUE, 'true-ish')
         self.assertEqual(TestConfiguration.IS_FALSE, False)
@@ -71,7 +78,8 @@ class TestFlaskEnv(unittest.TestCase):
         os.environ['LEADING_DOT'] = '.12'
         os.environ['IS_NOT_FLOAT'] = 'This is 6.5'
 
-        TestConfiguration = self._get_test_configuration()
+        # DEV: Set `env_load_all=True` to keep from having to make default values for each variable
+        TestConfiguration = self._get_test_configuration(env_load_all=True)
         self.assertEqual(TestConfiguration.IS_FLOAT, 12.5)
         self.assertEqual(TestConfiguration.TRAILING_DOT, 12.0)
         self.assertEqual(TestConfiguration.LEADING_DOT, 0.12)
@@ -84,7 +92,8 @@ class TestFlaskEnv(unittest.TestCase):
         os.environ['IS_ZERO'] = '0'
         os.environ['IS_NOT_INT'] = '12fa'
 
-        TestConfiguration = self._get_test_configuration()
+        # DEV: Set `env_load_all=True` to keep from having to make default values for each variable
+        TestConfiguration = self._get_test_configuration(env_load_all=True)
         self.assertEqual(TestConfiguration.IS_INT, 12)
         self.assertEqual(TestConfiguration.IS_ZERO, 0)
         self.assertEqual(TestConfiguration.IS_NOT_INT, '12fa')