Optional type args are mistyped in help

首先通过 fire.Fire(main) 重现这两个示例，并检查生成的 --help 输出。跟踪 Optional 注解如何转换为显示的类型，然后验证两个默认值都产生预期的 Optional[str] 表述。

Type annotations that use typing.Optional are incorrectly documented when showing help.

Example 1

from typing import Optional

import fire

def main(arg: Optional[str] = 'something'):
    """Do something with arg."""


if __name__ == '__main__':
    fire.Fire(main)

The corresponding help output is:

INFO: Showing help with the command 'firetest.py -- --help'.

NAME
    firetest.py - Do something with arg.

SYNOPSIS
    firetest.py <flags>

DESCRIPTION
    Do something with arg.

FLAGS
    -a, --arg=ARG
        Type: Optional
        Default: 'something'

Here, Type: Optional is totally incorrect. It should be Optional[str]. My use of str is just an example and it can be anything.

Example 2

from typing import Optional

import fire


def main(arg: Optional[str] = None):
    """Do something with arg."""


if __name__ == '__main__':
    fire.Fire(main)

The corresponding help output is:

INFO: Showing help with the command 'firetest.py -- --help'.

NAME
    firetest.py - Do something with arg.

SYNOPSIS
    firetest.py <flags>

DESCRIPTION
    Do something with arg.

FLAGS
    -a, --arg=ARG
        Type: Optional[Optional]
        Default: None

Here, Type: Optional[Optional] is even more incorrect. It should be Optional[str]. My use of str is just an example and it can be anything.