make file parsing optional

bison/__version__.py

@@ -3,7 +3,7 @@
 __title__ = 'bison'
 __description__ = 'Python application configuration'
 __url__ = 'https://github.com/edaniszewski/bison'
-__version__ = '0.0.3'
+__version__ = '0.0.4'
 __author__ = 'Erick Daniszewski'
 __author_email__ = 'edaniszewski@gmail.com'
 __license__ = 'MIT'

bison/bison.py

@@ -135,10 +135,15 @@ def validate(self):
         if self.scheme:
             self.scheme.validate(self.config)
 
-    def parse(self):
-        """Parse the configuration sources into `Bison`."""
+    def parse(self, requires_cfg=True):
+        """Parse the configuration sources into `Bison`.
+
+        Args:
+            requires_cfg (bool): Specify whether or not parsing should fail
+                if a config file is not found. (default: True)
+        """
         self._parse_default()
-        self._parse_config()
+        self._parse_config(requires_cfg)
         self._parse_env()
 
     def _find_config(self):
@@ -164,12 +169,21 @@ def _find_config(self):
         raise BisonError('No file named {} found in search paths {}'.format(
             self.config_name, self.config_paths))
 
-    def _parse_config(self):
+    def _parse_config(self, requires_cfg=True):
         """Parse the configuration file, if one is configured, and add it to
         the `Bison` state.
+
+        Args:
+            requires_cfg (bool): Specify whether or not parsing should fail
+                if a config file is not found. (default: True)
         """
         if len(self.config_paths) > 0:
-            self._find_config()
+            try:
+                self._find_config()
+            except BisonError:
+                if not requires_cfg:
+                    return
+                raise
             try:
                 with open(self.config_file, 'r') as f:
                     parsed = self._fmt_to_parser[self.config_format](f)

tests/test_bison.py

@@ -235,6 +235,39 @@ def test_parse_config_fail(self, bad_yaml_config):
         assert b.config_file == os.path.join(bad_yaml_config.dirname, bad_yaml_config.basename)
         assert len(b._config) == 0
 
+    def test_parse_config_not_required_found(self, yaml_config):
+        """Parse the file config when it isn't required."""
+        b = bison.Bison()
+        b.add_config_paths(yaml_config.dirname)
+
+        assert b.config_file is None
+        assert len(b._config) == 0
+
+        b._parse_config(requires_cfg=False)
+
+        assert b.config_file == os.path.join(yaml_config.dirname, yaml_config.basename)
+        assert len(b._config) == 2
+        assert b.config == {
+            'foo': True,
+            'bar': {
+                'baz': 1,
+                'test': 'value'
+            }
+        }
+
+    def test_parse_config_not_required_not_found(self):
+        """Parse the file config when it isn't required."""
+        b = bison.Bison()
+        b.add_config_paths('.')
+
+        assert b.config_file is None
+        assert len(b._config) == 0
+
+        b._parse_config(requires_cfg=False)
+
+        assert b.config_file is None
+        assert len(b._config) == 0
+
     def test_parse_defaults_no_scheme(self):
         """Parse the defaults when there is no Scheme."""
         b = bison.Bison()