Add support for "--" option

[atavakoli]

I'm requesting support for the POSIX-recommended, -- argument:

The argument ‘--’ terminates all options; any following arguments are treated as non-option arguments, even if they begin with a hyphen.

Encountering a -- could just add all the following arguments to the option having defaultOption: true, or to the _unknown property if no defaultOption is set and partial is true; otherwise, an exception could be thrown.

[75lb]

Hi, yes this functionality is planned for the next release. I will post more detail about how it will work here once I get sufficient time. Let me know if you have any further ideas or requests for improvement.

[atavakoli]

@75lb thanks. Which issue in that PR covers the -- option?

[75lb]

The idea was introduced by #53 and is still maturing (a WIP).

[75lb]

do you support the idea of having a stop parsing at first unknown feature? Some users would prefer if the first unknown option/value parsed acted as the -- style terminator.

In this example, the author could define options for -v and --os and enable the stop parsing at first unknown feature, meaning ls, -l and -a would be written to _unknown.

$ example -v --os centos ls -l -a

The above would be equivalent to this but saves the user needing to add --:

$ example -v --os centos -- ls -l -a

[atavakoli]

do you support the idea of having a stop parsing at first unknown feature?

I think this is a fair compromise, as people interested in implementing POSIX-style -- handling I can just check if the 1st unknown option is "--" and ignore it.

Just to be certain, what you're describing is the existing behavior when using {partial: true}, right?

[75lb]

no, "stop parsing at first unknown" is a new feature i'm planning to implement. The existing {partial: true} behaviour reports all unknown args. The "stop parsing at first unknown" will stop parsing altogether at the first unknown arg it meets, writing off the remaining args as _unknown whether they are known or not.

I'm not suggesting we compromise btw. We can have both "stop parsing at first unknown" and "stop parsing at --" as features.

[atavakoli]

Ah ok, that makes sense. From my side, I'm happy with whichever (or both) you decide to implement.

[75lb]

does this explanation of -- make sense?

You can try it using the prerelease.

$ npm install command-line-args@next

[75lb]

Implemented in v5.0.0.

[atavakoli]

Thanks @75lb, and the explanation makes sense (glad you went into detail on how to use it to remove ambiguity).

Looking forward to using it!