add loading config overrides from a filemount

.github/workflows/tests.yml

@@ -9,7 +9,6 @@ jobs:
     strategy:
       matrix:
         python-version:
-        - 3.9
         - '3.10'
         - 3.11
         - 3.12
@@ -23,7 +22,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install Dependencies
       run: |
-        python -m pip install .[tests]
+        python -m pip install .[tests,yaml]
     - name: Unit tests
       run: |
         make tests

docs/usage.rst

@@ -205,3 +205,34 @@ config object, you can specify the ENV_PREFIX attribute.
     >>> os.environ['FIGENV_USER'] = 'newuser'
     >>> Config.USER
     'newuser'
+
+Environment Files
+-----------------
+
+Some containerized runtimes use file mounts as a more secure access pattern for
+storing secrets. Figenv supports loading overrides for the config objects from
+those files. By default, it supports loading ``json`` data but if the ``yaml``
+extra is installed, then yaml environment files can be used.
+
+.. code-block:: yaml
+
+    # env.yaml
+    FOO: "eggs"
+    BAR: "spam"
+    BAZ: false
+
+.. code-block:: python
+
+    >>> import figenv
+    >>> class Config(metaclass=figenv.MetaConfig):
+    ...     ENV_FILE="files/test.json"
+    ...     FOO = "tofu"
+    ...     BAR = "tofurkey"
+    ...     BAZ = True
+    ...
+    >>> Config.FOO
+    'eggs'
+    >>> Config.BAR
+    'spam'
+    >>> Config.BAZ
+    False

figenv.py

@@ -21,6 +21,11 @@ class Config(metaclass=MetaConfig):
 except ImportError:
     NoneType = type(None)
 
+try:
+    import yaml
+except ImportError:
+    yaml = None
+
 _MISSING = type("MISSING", (object,), {"__repr__": lambda self: "<MISSING CONFIGURATION>"})()
 
 
@@ -33,7 +38,7 @@ def __init__(self, name, message=None):
 
 
 def _check_special_names(name):
-    return name in ('name', 'keys') or name.startswith('_')
+    return name in ('name', 'keys', 'environ') or name.startswith('_')
 
 
 def strict(f):
@@ -46,6 +51,16 @@ class MetaConfig(type):
     def __init__(cls, name, bases, dict):
         super().__init__(name, bases, dict)
         cls.name = name
+        cls.environ = os.environ
+        if "ENV_FILE" in dict:
+            if os.path.exists(dict["ENV_FILE"]):
+                with open(dict["ENV_FILE"]) as fh_:
+                    if yaml is not None:
+                        cls.environ = yaml.safe_load(fh_)
+                    else:
+                        cls.environ = json.load(fh_)
+            else:
+                print(f"Failed to load env_file: {dict['ENV_FILE']}")
         cls._dict = {}
         for base in bases:
             if not hasattr(base, '_dict'):
@@ -150,7 +165,7 @@ def __getattr__(cls, name):
         prefix = cls._dict.get('ENV_PREFIX', '')
         load_all = cls._dict.get('ENV_LOAD_ALL', False)
 
-        if (not load_all and name not in cls._dict) or (name not in cls._dict and prefix + name not in os.environ):
+        if (not load_all and name not in cls._dict) or (name not in cls._dict and prefix + name not in cls.environ):
             raise AttributeError(f"type object {cls.name} has no attribute '{name}'")
 
         value = func = cls._dict.get(name, _MISSING)
@@ -159,8 +174,8 @@ def __getattr__(cls, name):
         if callable(value) and getattr(func, "_strict", False):
             override_via_environment = False
 
-        if override_via_environment and prefix + name in os.environ:
-            value = os.environ[prefix + name]
+        if override_via_environment and prefix + name in cls.environ:
+            value = cls.environ[prefix + name]
 
         if value is _MISSING:
             # Configuration with no default and no value in the environment

files/test.json

@@ -0,0 +1,5 @@
+{
+    "FOO": "eggs",
+    "BAR": "spam",
+    "BAZ": false
+}

files/test.yaml

@@ -0,0 +1,3 @@
+FOO: eggs
+BAR: spam
+BAZ: false

setup.cfg

@@ -33,6 +33,9 @@ tests =
     codecov
     black
     unittest-xml-reporting
+    unittest2
 docs =
     sphinx
     sphinx-rtd-theme
+yaml =
+    pyyaml

test.py

@@ -6,6 +6,7 @@
 import xmlrunner
 
 
+import figenv
 from figenv import MetaConfig, strict, MissingConfigurationException, _MISSING
 
 
@@ -70,6 +71,44 @@ def test_default_settings(self):
         with self.assertRaises(RuntimeError):
             TestConfiguration["NO_DEFAULT_SETTING"]
 
+    def test_env_file_settings(self):
+        """Test that if the env file is set, settings get loaded from it."""
+        TestConfiguration = self._get_test_configuration(
+            ENV_FILE="files/test.json",
+            FOO='no',
+            BAR='yes',
+            BAZ=True,
+        )
+        self.assertEqual(TestConfiguration.FOO, 'eggs')
+        self.assertEqual(TestConfiguration.BAR, 'spam')
+        self.assertEqual(TestConfiguration.BAZ, False)
+
+    def test_env_file_settings_json(self):
+        """Test that if the env file is set, settings get loaded from it."""
+        figenv.yaml = None
+        TestConfiguration = self._get_test_configuration(
+            ENV_FILE="files/test.json",
+            FOO='no',
+            BAR='yes',
+            BAZ=True,
+        )
+        self.assertEqual(TestConfiguration.FOO, 'eggs')
+        self.assertEqual(TestConfiguration.BAR, 'spam')
+        self.assertEqual(TestConfiguration.BAZ, False)
+
+    def test_env_file_settings_missing_file(self):
+        """Test that if the env file is set, but file is missing, defaults are used"""
+        figenv.yaml = None
+        TestConfiguration = self._get_test_configuration(
+            ENV_FILE="files/missing.json",
+            FOO='no',
+            BAR='yes',
+            BAZ=True,
+        )
+        self.assertEqual(TestConfiguration.FOO, 'no')
+        self.assertEqual(TestConfiguration.BAR, 'yes')
+        self.assertEqual(TestConfiguration.BAZ, True)
+
     def test_invalid_setter(self):
         """users should not be able to set variables using attributes"""
         TestConfiguration = self._get_test_configuration(DEFAULT_SETTING='default_value', BOOL_SETTING=True)