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Unclear behavior with defaultOption and more-than-one multiple args

See original GitHub issue

Given this config:

const optionDefinitions = [
  { name: 'verbose', alias: 'v', type: Boolean },
  { name: 'src', type: String, multiple: true },
  { name: 'foo', type: String, multiple: true, defaultOption: true },
  { name: 'timeout', alias: 't', type: Number }

It is not clear what would be the behavior for:

$ example --verbose --timeout=1000 --src one.js two.js three.js

What’s clear here:

  • one.js is one of the src values.

What’s not clear here:

  • Are two.js and three.js values for src, or foo?

The common-best-practice (specifically in unix-like systems) is to have two.js and three.js as foo values. However, the examples in have a light indication that these values would be considered as src’s. (At least some people that I have talked to have had this understanding from the doc.)

Would be great if we could make this more clear in the docs.

Issue Analytics

  • State:closed
  • Created a year ago
  • Comments:5 (3 by maintainers)

github_iconTop GitHub Comments

75lbcommented, Apr 22, 2022

enabling multiple plugins would be like -p first.js -p second.js -p "more-plugins/*.js" (the command would be responsible for glob expansion).

the majority of users don’t quote glob expressions, meaning the shell expands the glob expression before passing the result into node… this results in command-line-args parsing a process.argv looking something like ['-p', 'more-plugins/one.js', 'more-plugins/two.js', 'more-plugins/three.js'] (i.e. an option followed by one or more values)… We need to support this form…

And GNU adds the long options (doube-hyphen), allowing --plugin first.js --plugin second.js ....

Use lazyMultiple to get this syntax form in command-line-args…

Thanks for the feedback - if you have ideas to improve the documentation, feel free to edit the wiki or submit a PR… i too will review the docs when I get round to working on the next version…

besfahbodcommented, Apr 21, 2022

So, in POSIX proper, enabling multiple plugins would be like -p first.js -p second.js -p "more-plugins/*.js" (the command would be responsible for glob expansion).

And GNU adds the long options (doube-hyphen), allowing --plugin first.js --plugin second.js ....

I think the idea is that if you expect many arguments of some kind, you would make sure there’s a short form for it, keeping the overhead low.

That said, the POSIX and GNU behaviors are kind of ancient now, and some newer major products actually use something a bit more flexible than that. However, I’m not familiar with any major system behavior the way this project does.

I wanted to refer to the docs for Rust’s clap library on how they handle multiple occurrences (which I believe should be GNU-friendly), however I couldn’t find it in the docs, and I think we need to write a demo for it to show how it behaves… (

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