Custom default label ignored if default is None

[ziima]

I found out that custom default label is not shown when default is None. In some cases default = None is intentional, but custom default label would be still helpful.

An example with --limit option, with None as default meaning no limit:

import click

@click.command()
@click.option('--limit', type=int, show_default='unlimited')
def main(limit: int):
    print('Limit: {}'.format(limit))

if __name__ == '__main__':
    main()

Expected Behavior

Tell us what should happen.

$ python3 /tmp/foo.py --help
Usage: foo.py [OPTIONS]

Options:
  --limit INTEGER  [default: unlimited]
  --help           Show this message and exit.

Actual Behavior

Tell us what happens instead.

$ python3 /tmp/foo.py --help
Usage: foo.py [OPTIONS]

Options:
  --limit INTEGER
  --help           Show this message and exit.

Default is not shown, making the description less useful.

Environment

• Python version: 3.9.1
• Click version: 7.1.2

[b3n4kh]

show_default is supposed to be a Boolean, triggering to show the value in default. Since there is no default set I think the best would be to just set help='[default: unlimited]'.

Otherwise you could achive your result with:

import click

@click.command()
@click.option('--limit', type=int, show_default='unlimited', default=-1)
def main(limit: int):
    if limit >= 0:
      print('Limit: {}'.format(limit))

if __name__ == '__main__':
    main()

[ziima]

According to docs, string is a perfectly valid value for a show_default, see https://click.palletsprojects.com/en/7.x/api/?highlight=show_default#click.Option.

Yes, I found out it works, when I change the default value to something else, but that's not something I want to do. It makes code less readable.