Argparse compat extensions

argparse_compat.py

# SPDX-FileCopyrightText: 2024 mara004 <geisserml@gmail.com>
# SPDX-License-Identifier: Apache-2.0 OR BSD-3-Clause OR CC-BY-4.0

import sys
import argparse

if sys.version_info >= (3, 9):
    from argparse import BooleanOptionalAction

else:

    # backport, adapted from argparse sources
    class BooleanOptionalAction (argparse.Action):
        
        def __init__(self, option_strings, dest, **kwargs):
            _option_strings = []
            for option_string in option_strings:
                _option_strings.append(option_string)

                if option_string.startswith('--'):
                    option_string = '--no-' + option_string[2:]
                    _option_strings.append(option_string)

            super().__init__(option_strings=_option_strings, dest=dest, nargs=0, **kwargs)

        def __call__(self, parser, namespace, values, option_string=None):
            if option_string in self.option_strings:
                setattr(namespace, self.dest, not option_string.startswith('--no-'))

        def format_usage(self):
            return ' | '.join(self.option_strings)


if sys.version_info < (3, 8):

    class ExtendAction (argparse.Action):
        def __call__(self, parser, namespace, values, option_string=None):
            items = getattr(namespace, self.dest) or []
            items.extend(values)
            setattr(namespace, self.dest, items)

    # then do parser.register('action', 'extend', ExtendAction) on your parser instance