Create _ExtendArgument

pylint/config/argument.py

@@ -27,8 +27,9 @@
 
 from pylint import interfaces
 from pylint import utils as pylint_utils
-from pylint.config.callback_actions import _CallbackAction
+from pylint.config.callback_actions import _CallbackAction, _ExtendAction
 from pylint.config.deprecation_actions import _NewNamesAction, _OldNamesAction
+from pylint.constants import PY38_PLUS
 
 if sys.version_info >= (3, 8):
     from typing import Literal
@@ -294,7 +295,7 @@ def __init__(
         self,
         *,
         flags: List[str],
-        action: Type[argparse._StoreAction],
+        action: Type[argparse.Action],
         default: _ArgumentTypes,
         arg_type: str,
         choices: Optional[List[str]],
@@ -330,6 +331,50 @@ def __init__(
         """
 
 
+class _ExtendArgument(_DeprecationArgument):
+    """Class for extend arguments to be parsed by an argparse.ArgumentsParser.
+
+    This is based on the parameters passed to argparse.ArgumentsParser.add_message.
+    See:
+    https://docs.python.org/3/library/argparse.html#argparse.ArgumentParser.add_argument
+    """
+
+    def __init__(
+        self,
+        *,
+        flags: List[str],
+        action: Literal["extend"],
+        default: _ArgumentTypes,
+        arg_type: str,
+        metavar: str,
+        arg_help: str,
+        hide_help: bool,
+        section: Optional[str],
+        choices: Optional[List[str]],
+        dest: Optional[str],
+    ) -> None:
+        # The extend action is included in the stdlib from 3.8+
+        if PY38_PLUS:
+            action_class = argparse._ExtendAction  # type: ignore[attr-defined]
+        else:
+            action_class = _ExtendAction
+
+        self.dest = dest
+        """The destination of the argument."""
+
+        super().__init__(
+            flags=flags,
+            action=action_class,
+            default=default,
+            arg_type=arg_type,
+            choices=choices,
+            arg_help=arg_help,
+            metavar=metavar,
+            hide_help=hide_help,
+            section=section,
+        )
+
+
 class _StoreOldNamesArgument(_DeprecationArgument):
     """Store arguments while also handling old names.
 

pylint/config/arguments_manager.py

@@ -23,6 +23,7 @@
 from pylint.config.argument import (
     _Argument,
     _CallableArgument,
+    _ExtendArgument,
     _StoreArgument,
     _StoreNewNamesArgument,
     _StoreOldNamesArgument,
@@ -191,6 +192,17 @@ def _add_parser_option(
                 action=argument.action,
                 help=argument.help,
             )
+        elif isinstance(argument, _ExtendArgument):
+            section_group.add_argument(
+                *argument.flags,
+                action=argument.action,
+                default=argument.default,
+                type=argument.type,  # type: ignore[arg-type] # incorrect typing in typeshed
+                help=argument.help,
+                metavar=argument.metavar,
+                choices=argument.choices,
+                dest=argument.dest,
+            )
         else:
             raise UnrecognizedArgumentAction
 

pylint/config/arguments_provider.py

@@ -132,6 +132,18 @@ def set_option(self, optname, value, action=None, optdict=None):
                 setattr(self.config, optname, _list + (value,))
             else:
                 _list.append(value)
+        elif action == "extend":
+            _list = getattr(self.config, optname, None)
+            if _list is None:
+                if isinstance(value, (list, tuple)):
+                    _list = value
+                elif value is not None:
+                    _list = [value]
+                setattr(self.config, optname, _list)
+            elif isinstance(_list, tuple):
+                setattr(self.config, optname, _list + (value,))
+            else:
+                _list.extend(value)
         elif (
             action == "callback"
             or (not isinstance(action, str))

pylint/config/callback_actions.py

@@ -52,6 +52,27 @@ def __call__(
         return None
 
 
+class _ExtendAction(argparse._AppendAction):
+    """Action that adds the value to a pre-existing list.
+
+    It is directly copied from the stdlib implementation which is only available
+    on 3.8+.
+    """
+
+    def __call__(
+        self,
+        parser: argparse.ArgumentParser,
+        namespace: argparse.Namespace,
+        values: Union[str, Sequence[Any], None],
+        option_string: Optional[str] = None,
+    ) -> None:
+        assert isinstance(values, (tuple, list))
+        current = getattr(namespace, self.dest, [])
+        assert isinstance(current, list)
+        current.extend(values)
+        setattr(namespace, self.dest, current)
+
+
 class _AccessRunObjectAction(_CallbackAction):
     """Action that has access to the Run object."""
 

pylint/config/utils.py

@@ -13,6 +13,7 @@
 from pylint import extensions, utils
 from pylint.config.argument import (
     _CallableArgument,
+    _ExtendArgument,
     _StoreArgument,
     _StoreNewNamesArgument,
     _StoreOldNamesArgument,
@@ -33,6 +34,7 @@ def _convert_option_to_argument(
     _CallableArgument,
     _StoreOldNamesArgument,
     _StoreNewNamesArgument,
+    _ExtendArgument,
 ]:
     """Convert an optdict to an Argument class instance."""
     if "level" in optdict and "hide" not in optdict:
@@ -84,7 +86,19 @@ def _convert_option_to_argument(
             DeprecationWarning,
         )
         default = None
-
+    if action == "extend":
+        return _ExtendArgument(
+            flags=flags,
+            action=action,
+            default=default,
+            arg_type=optdict["type"],
+            choices=choices,
+            arg_help=optdict.get("help", ""),
+            metavar=optdict.get("metavar", ""),
+            hide_help=optdict.get("hide", False),
+            section=optdict.get("group", None),
+            dest=optdict.get("dest", None),
+        )
     if "kwargs" in optdict:
         if "old_names" in optdict["kwargs"]:
             return _StoreOldNamesArgument(