import json


def get_arg_list(arg_value, default_value=None):
    """Returns list of values from argument provided. Backwards compatible for JSON input.

    arg_value (str): Argument supplied
    default_value (Any): A default value to supply when arg_value is empty.
    """
    if not arg_value:
        return default_value

    try:
        arg_list = json.loads(arg_value)
    except json.decoder.JSONDecodeError:
        arg_list = arg_value.split(",")
    return arg_list