remove Optional[] annotation wrappers where redundant

deoptional.py

"""
Optional[] is implied in arguments when the default value is None. Leaving it
out is a matter of personal preference and I prefer to leave it out in favor of
shorter lines with not obvious behavior.

This script removes unnecessary Optional declarations in arguments.

WARNING: this updates files in-place.
"""

import redbaron
import argparse


def remove_redundant_optional(source):
    for node in source.find_all(
        'DefArgumentNode',
        value=lambda v: v and v.value == 'None',
        annotation=lambda a: a and a.name.value == "Optional"
    ):
        node.annotation = node.annotation.getitemnode.value


def main(filename):
    with open(filename, 'r') as file:
        source = redbaron.RedBaron(file.read())

    remove_redundant_optional(source)

    with open(filename, 'w') as file:
        file.write(source.dumps())


if __name__ == "__main__":
    parser = argparse.ArgumentParser(__doc__)
    parser.add_argument("filename")
    args = parser.parse_args()

    main(args.filename)