Merge branch 'optmgr-parse-unknown-default-values' into 'master'

Set configuration file-provided values via ArgumentParser.set_defaults()

See merge request pycqa/flake8!349

src/flake8/options/manager.py

@@ -426,12 +426,18 @@ class OptionManager(object):
         )
 
     def parse_args(self, args=None, values=None):
+        # type: (Optional[List[str]], Optional[argparse.Namespace]) -> Tuple[argparse.Namespace, List[str]]  # noqa: E501
         """Proxy to calling the OptionParser's parse_args method."""
         self.generate_epilog()
         self.update_version_string()
-        args = self.parser.parse_args(args, values)
+        assert isinstance(  # nosec (for bandit)
+            self.parser, argparse.ArgumentParser
+        ), self.parser
+        if values:
+            self.parser.set_defaults(**vars(values))
+        parsed_args = self.parser.parse_args(args)
         # TODO: refactor callers to not need this
-        return args, args.filenames
+        return parsed_args, parsed_args.filenames
 
     def parse_known_args(self, args=None):
         # type: (Optional[List[str]]) -> Tuple[argparse.Namespace, List[str]]

tests/unit/test_option_manager.py

@@ -22,6 +22,21 @@ def test_option_manager_creates_option_parser(optmanager):
     assert isinstance(optmanager.parser, argparse.ArgumentParser)
 
 
+def test_parse_args_forwarding_default_values(optmanager):
+    """Verify default provided values are present in the final result."""
+    namespace = argparse.Namespace(foo='bar')
+    options, args = optmanager.parse_args([], namespace)
+    assert options.foo == 'bar'
+
+
+def test_parse_args_forwarding_type_coercion(optmanager):
+    """Verify default provided values are type converted from add_option."""
+    optmanager.add_option('--foo', type=int)
+    namespace = argparse.Namespace(foo='5')
+    options, args = optmanager.parse_args([], namespace)
+    assert options.foo == 5
+
+
 def test_add_option_short_option_only(optmanager):
     """Verify the behaviour of adding a short-option only."""
     assert optmanager.options == []