Add no_args_is_help to click.Command

[sirosen]

The functionality for no_args_is_help, available on MultiCommands, can easily be added on Commands as well. The result is not much more code, and a more consistent interface between MultiCommands and Commands.
It's also nice to be able to write a click command foo and then just hit foo for help, regardless of whether its a Group or Command.

closes #1156

Will add changelog edit in a moment, after this PR is assigned a number.

[sirosen]

I just had a coworker ask me about this feature (unaware of this PR), so I guess that's a 👍 from somewhere for this feature.

In #1156 I said I wasn't sure we needed this, but maybe I'm changing my tune on it. Seems easy for click to do, and confusing for people new to the framework.

[davidism]

Looks good to me.

Should there be a check that there is at least one required arg? Otherwise you wouldn't actually be able to run the command. Guess at that point you should have just not set no_args_is_help though.

[sirosen]

Yeah, I think "just don't try to do that" is a reasonable stance.
I wouldn't check for a required arg, since someone might have a command which takes a bunch of options which determine its behavior. e.g. command --mode1 and command --mode2 are valid, but command on its own is not.

I noticed a small typo in my changelog entry, which I just amended. That's why there's a fresh commit.

[simonkeng]

Hi, do developers need to wait for the 7.1 release to use this feature? Or is there a branch I can switch to in order to have access to this earlier? I'm using Click==7.0 via pip but I would build it from the GitHub repo instead if I can access no_args_is_help without waiting for the 7.1 release.

Thanks!

[sirosen]

@simonkeng, if you want to use this ahead of the 7.1 release, you could install from the 7.x branch directly or even from a specific commit on said branch.
I don't recommend this, but it works and you can do it. It's just a "buyer beware" situation.

There are a few ways to install from GitHub with pip, but here's one which doesn't require you to have git installed on the target platform:
pip install https://github.com/pallets/click/archive/7.x.tar.gz
or
pip install https://github.com/pallets/click/archive/6245807b95a01ff3538f06bcc93e38042474aca9.tar.gz

You might be better served (until 7.1 releases) by just printing the helptext yourself with

# TODO: remove after click 7.1 releases and use no_args_is_help instead
if not (arg1 or arg2):
    click.echo(ctx.get_help(), color=ctx.color)

if you pass the context to your commands.

If I needed this behavior in my own tools, I'd probably opt for explicitly printing help myself.