Update from_yaml() method

src/dependency_injector/providers.pyx

@@ -1339,7 +1339,7 @@ cdef class ConfigurationOption(Provider):
             current_config = {}
         self.override(merge_dicts(current_config, config))
 
-    def from_yaml(self, filepath, loader=None):
+    def from_yaml(self, filepath, required=UNDEFINED, loader=None):
         """Load configuration from the yaml file.
 
         Loaded configuration is merged recursively over existing configuration.
@@ -1347,6 +1347,9 @@ cdef class ConfigurationOption(Provider):
         :param filepath: Path to the configuration file.
         :type filepath: str
 
+        :param required: When required is True, raise an exception if file does not exist.
+        :type required: bool
+
         :param loader: YAML loader, :py:class:`YamlLoader` is used if not specified.
         :type loader: ``yaml.Loader``
 
@@ -1367,7 +1370,9 @@ cdef class ConfigurationOption(Provider):
             with open(filepath) as opened_file:
                 config = yaml.load(opened_file, loader)
         except IOError as exception:
-            if self._is_strict_mode_enabled() and exception.errno in (errno.ENOENT, errno.EISDIR):
+            if required is not False \
+                    and (self._is_strict_mode_enabled() or required is True) \
+                    and exception.errno in (errno.ENOENT, errno.EISDIR):
                 exception.strerror = 'Unable to load configuration file {0}'.format(exception.strerror)
                 raise
             return
@@ -1648,7 +1653,7 @@ cdef class Configuration(Object):
             current_config = {}
         self.override(merge_dicts(current_config, config))
 
-    def from_yaml(self, filepath, loader=None):
+    def from_yaml(self, filepath, required=UNDEFINED, loader=None):
         """Load configuration from the yaml file.
 
         Loaded configuration is merged recursively over existing configuration.
@@ -1656,6 +1661,9 @@ cdef class Configuration(Object):
         :param filepath: Path to the configuration file.
         :type filepath: str
 
+        :param required: When required is True, raise an exception if file does not exist.
+        :type required: bool
+
         :param loader: YAML loader, :py:class:`YamlLoader` is used if not specified.
         :type loader: ``yaml.Loader``
 
@@ -1675,7 +1683,9 @@ cdef class Configuration(Object):
             with open(filepath) as opened_file:
                 config = yaml.load(opened_file, loader)
         except IOError as exception:
-            if self._is_strict_mode_enabled() and exception.errno in (errno.ENOENT, errno.EISDIR):
+            if required is not False \
+                    and (self._is_strict_mode_enabled() or required is True) \
+                    and exception.errno in (errno.ENOENT, errno.EISDIR):
                 exception.strerror = 'Unable to load configuration file {0}'.format(exception.strerror)
                 raise
             return

tests/unit/providers/test_configuration_py2_py3.py

@@ -565,6 +565,25 @@ class ConfigFromYamlTests(unittest.TestCase):
         with self.assertRaises(IOError):
             self.config.option.from_yaml('./does_not_exist.yml')
 
+    def test_required_file_does_not_exist(self):
+        with self.assertRaises(IOError):
+            self.config.from_yaml('./does_not_exist.yml', required=True)
+
+    def test_required_option_file_does_not_exist(self):
+        with self.assertRaises(IOError):
+            self.config.option.from_yaml('./does_not_exist.yml', required=True)
+
+    def test_not_required_file_does_not_exist_strict_mode(self):
+        self.config = providers.Configuration(strict=True)
+        self.config.from_yaml('./does_not_exist.yml', required=False)
+        self.assertEqual(self.config(), {})
+
+    def test_not_required_option_file_does_not_exist_strict_mode(self):
+        self.config = providers.Configuration(strict=True)
+        self.config.option.from_yaml('./does_not_exist.yml', required=False)
+        with self.assertRaises(errors.Error):
+            self.config.option()
+
     def test_no_yaml_installed(self):
         @contextlib.contextmanager
         def no_yaml_module():