Make prototype with enterpolation before parsing

src/dependency_injector/providers.pyi

@@ -201,7 +201,7 @@ class ConfigurationOption(Provider[Any]):
     def is_required(self) -> bool: ...
     def update(self, value: Any) -> None: ...
     def from_ini(self, filepath: Union[Path, str], required: bool = False) -> None: ...
-    def from_yaml(self, filepath: Union[Path, str], required: bool = False, loader: Optional[Any]=None) -> None: ...
+    def from_yaml(self, filepath: Union[Path, str], required: bool = False, loader: Optional[Any] = None, envs_required: bool = False) -> None: ...
     def from_pydantic(self, settings: PydanticSettings, required: bool = False, **kwargs: Any) -> None: ...
     def from_dict(self, options: _Dict[str, Any], required: bool = False) -> None: ...
     def from_env(self, name: str, default: Optional[Any] = None, required: bool = False) -> None: ...
@@ -238,7 +238,7 @@ class Configuration(Object[Any]):
     def reset_cache(self) -> None: ...
     def update(self, value: Any) -> None: ...
     def from_ini(self, filepath: Union[Path, str], required: bool = False) -> None: ...
-    def from_yaml(self, filepath: Union[Path, str], required: bool = False, loader: Optional[Any]=None) -> None: ...
+    def from_yaml(self, filepath: Union[Path, str], required: bool = False, loader: Optional[Any] = None, envs_required: bool = False) -> None: ...
     def from_pydantic(self, settings: PydanticSettings, required: bool = False, **kwargs: Any) -> None: ...
     def from_dict(self, options: _Dict[str, Any], required: bool = False) -> None: ...
     def from_env(self, name: str, default: Optional[Any] = None, required: bool = False) -> None: ...

src/dependency_injector/providers.pyx

@@ -68,15 +68,18 @@ config_env_marker_pattern = re.compile(
     r'\${(?P<name>[^}^{:]+)(?P<separator>:?)(?P<default>.*?)}',
 )
 
-def _resolve_config_env_markers(config_value):
+def _resolve_config_env_markers(config_value, envs_required=False):
-    """"Replace environment variable markers with their values."""
+    """Replace environment variable markers with their values."""
-    for match in reversed(list(config_env_marker_pattern.finditer(config_value))):
+    findings = list(config_env_marker_pattern.finditer(config_value))
+
+    for match in reversed(findings):
+        env_name = match.group('name')
         has_default = match.group('separator') == ':'
 
-        value = os.getenv(match.group('name'))
+        value = os.getenv(env_name)
         if value is None:
-            if not has_default:
+            if not has_default and envs_required:
-                continue
+                raise ValueError(f'Missing required environment variable "{env_name}"')
             value = match.group('default')
 
         span_min, span_max = match.span()
@@ -85,17 +88,11 @@ def _resolve_config_env_markers(config_value):
 
 
 if sys.version_info[0] == 3:
-    class EnvInterpolation(iniconfigparser.BasicInterpolation):
-        """Interpolation which expands environment variables in values."""
-
-        def before_get(self, parser, section, option, value, defaults):
-            value = super().before_get(parser, section, option, value, defaults)
-            return _resolve_config_env_markers(value)
-
     def _parse_ini_file(filepath):
-        parser = iniconfigparser.ConfigParser(interpolation=EnvInterpolation())
+        parser = iniconfigparser.ConfigParser()
         with open(filepath) as config_file:
-            parser.read_file(config_file)
+            config_string = _resolve_config_env_markers(config_file.read())
+        parser.read_string(config_string)
         return parser
 else:
     import StringIO
@@ -109,27 +106,16 @@ else:
 
 
 if yaml:
-    # TODO: use SafeLoader without env interpolation by default in version 5.*
-    def yaml_env_marker_constructor(_, node):
-        """"Replace environment variable marker with its value."""
-        return _resolve_config_env_markers(node.value)
-
-    yaml.add_implicit_resolver('!path', config_env_marker_pattern)
-    yaml.add_constructor('!path', yaml_env_marker_constructor)
-
     class YamlLoader(yaml.SafeLoader):
-        """Custom YAML loader.
+        """YAML loader.
 
-        Inherits ``yaml.SafeLoader`` and add environment variables interpolation.
+        This loader mimics ``yaml.SafeLoader``.
         """
-
-    YamlLoader.add_implicit_resolver('!path', config_env_marker_pattern, None)
-    YamlLoader.add_constructor('!path', yaml_env_marker_constructor)
 else:
     class YamlLoader:
-        """Custom YAML loader.
+        """YAML loader.
 
-        Inherits ``yaml.SafeLoader`` and add environment variables interpolation.
+        This loader mimics ``yaml.SafeLoader``.
         """
 
 
@@ -1567,7 +1553,7 @@ cdef class ConfigurationOption(Provider):
             current_config = {}
         self.override(merge_dicts(current_config, config))
 
-    def from_yaml(self, filepath, required=UNDEFINED, loader=None):
+    def from_yaml(self, filepath, required=UNDEFINED, loader=None, envs_required=False):
         """Load configuration from the yaml file.
 
         Loaded configuration is merged recursively over existing configuration.
@@ -1581,6 +1567,9 @@ cdef class ConfigurationOption(Provider):
         :param loader: YAML loader, :py:class:`YamlLoader` is used if not specified.
         :type loader: ``yaml.Loader``
 
+        :param envs_required: When True, raises an error on undefined environment variable.
+        :type envs_required: bool
+
         :rtype: None
         """
         if yaml is None:
@@ -1595,7 +1584,7 @@ cdef class ConfigurationOption(Provider):
 
         try:
             with open(filepath) as opened_file:
-                config = yaml.load(opened_file, loader)
+                config_content = opened_file.read()
         except IOError as exception:
             if required is not False \
                     and (self._is_strict_mode_enabled() or required is True) \
@@ -1604,6 +1593,12 @@ cdef class ConfigurationOption(Provider):
                 raise
             return
 
+        config_content = _resolve_config_env_markers(
+            config_content,
+            envs_required=envs_required,
+        )
+        config = yaml.load(config_content, loader)
+
         current_config = self.__call__()
         if not current_config:
             current_config = {}
@@ -1988,7 +1983,7 @@ cdef class Configuration(Object):
             current_config = {}
         self.override(merge_dicts(current_config, config))
 
-    def from_yaml(self, filepath, required=UNDEFINED, loader=None):
+    def from_yaml(self, filepath, required=UNDEFINED, loader=None, envs_required=False):
         """Load configuration from the yaml file.
 
         Loaded configuration is merged recursively over existing configuration.
@@ -2002,6 +1997,9 @@ cdef class Configuration(Object):
         :param loader: YAML loader, :py:class:`YamlLoader` is used if not specified.
         :type loader: ``yaml.Loader``
 
+        :param envs_required: When True, raises an error on undefined environment variable.
+        :type envs_required: bool
+
         :rtype: None
         """
         if yaml is None:
@@ -2016,7 +2014,7 @@ cdef class Configuration(Object):
 
         try:
             with open(filepath) as opened_file:
-                config = yaml.load(opened_file, loader)
+                config_content = opened_file.read()
         except IOError as exception:
             if required is not False \
                     and (self._is_strict_mode_enabled() or required is True) \
@@ -2025,6 +2023,12 @@ cdef class Configuration(Object):
                 raise
             return
 
+        config_content = _resolve_config_env_markers(
+            config_content,
+            envs_required=envs_required,
+        )
+        config = yaml.load(config_content, loader)
+
         current_config = self.__call__()
         if not current_config:
             current_config = {}

tests/unit/providers/test_configuration_py2_py3.py

@@ -639,20 +639,20 @@ class ConfigFromIniWithEnvInterpolationTests(unittest.TestCase):
             self.config(),
             {
                 'section1': {
-                    'value1': '${CONFIG_TEST_ENV}',
+                    'value1': '',
-                    'value2': '${CONFIG_TEST_PATH}/path',
+                    'value2': '/path',
                 },
             },
         )
         self.assertEqual(
             self.config.section1(),
             {
-                'value1': '${CONFIG_TEST_ENV}',
+                'value1': '',
-                'value2': '${CONFIG_TEST_PATH}/path',
+                'value2': '/path',
             },
         )
-        self.assertEqual(self.config.section1.value1(), '${CONFIG_TEST_ENV}')
+        self.assertEqual(self.config.section1.value1(), '')
-        self.assertEqual(self.config.section1.value2(), '${CONFIG_TEST_PATH}/path')
+        self.assertEqual(self.config.section1.value2(), '/path')
 
     def test_default_values(self):
         os.environ['DEFINED'] = 'defined'
@@ -673,7 +673,7 @@ class ConfigFromIniWithEnvInterpolationTests(unittest.TestCase):
             {
                 'defined_with_default': 'defined',
                 'undefined_with_default': 'default',
-                'complex': 'defined/path/defined/${UNDEFINED}/default',
+                'complex': 'defined/path/defined//default',
             },
         )
 
@@ -890,20 +890,20 @@ class ConfigFromYamlWithEnvInterpolationTests(unittest.TestCase):
             self.config(),
             {
                 'section1': {
-                    'value1': '${CONFIG_TEST_ENV}',
+                    'value1': None,
-                    'value2': '${CONFIG_TEST_PATH}/path',
+                    'value2': '/path',
                 },
             },
         )
         self.assertEqual(
             self.config.section1(),
             {
-                'value1': '${CONFIG_TEST_ENV}',
+                'value1': None,
-                'value2': '${CONFIG_TEST_PATH}/path',
+                'value2': '/path',
             },
         )
-        self.assertEqual(self.config.section1.value1(), '${CONFIG_TEST_ENV}')
+        self.assertIsNone(self.config.section1.value1())
-        self.assertEqual(self.config.section1.value2(), '${CONFIG_TEST_PATH}/path')
+        self.assertEqual(self.config.section1.value2(), '/path')
 
     @unittest.skipIf(sys.version_info[:2] == (3, 4), 'PyYAML does not support Python 3.4')
     def test_default_values(self):
@@ -925,7 +925,7 @@ class ConfigFromYamlWithEnvInterpolationTests(unittest.TestCase):
             {
                 'defined_with_default': 'defined',
                 'undefined_with_default': 'default',
-                'complex': 'defined/path/defined/${UNDEFINED}/default',
+                'complex': 'defined/path/defined//default',
             },
         )