Pass custom HelpFormatter to subparsers

[zrlf]

When using a custom HelpFormatter, subparsers are still using the default SimpleHelpFormatter.

To Reproduce

from simple_parsing import ArgumentParser
from dataclasses import dataclass

@dataclass
class Sub:
   foo: str

@dataclass
class Foo:
   subcommand: Union[Sub, SomeOther]
   bar: int = 123

if __name__ == "__main__":
   parser = ArgumentParser(formatter_class=CustomHelpFormatter)
   parser.add_arguments(Foo, "foo")
   args = parser.parse_args(["sub", "-h"])

Expected behavior
Any subparser should inherit the formatter.

Actual behavior
Default is used

[zrlf]

Looks like a simple fix. In line 1023, replacing with subparser = subparsers.add_parser(subcommand, formatter_class=parser.formatter_class) fixes this issue.

SimpleParsing/simple_parsing/wrappers/field_wrapper.py

Lines 1021 to 1023 in 4388893

	for subcommand, dataclass_type in self.subparsers_dict.items():
	logger.debug(f"adding subparser '{subcommand}' for type {dataclass_type}")
	subparser = subparsers.add_parser(subcommand)

[lebrice]

Hey @zrlf , nice catch! Would you like to make a PR? :)

[zrlf]

sure :)