Enable boolean flags parsing in CLI

[pvdlg]

Currently the semicolon and prettier parsing by meow had to be disabled, as if they are not used by the user, meow set them to false and they override the configuration file.

So setting "semicolon": true or "prettier": true in the package.json is always overwritten and set to false.

Investigating it's related to to minimist which is used internally by meow. See https://github.com/substack/minimist/issues/94.

minimist doesn't seems to be maintained anymore and didn't received any commits for more than 2 years.

In order to solve this issue I see a couple solutions:

• Replace meow by another arg parsing solution. In my experience yargs seems to be the most complete, reliable and maintained solution. Caporal.js seems promising as well.
• Replace minimist inside meow by another solution. yargs-parser seems a good candidate.

@sindresorhus as you are also the author of meow, how would you prefer to address that issue?

[kevva]

@pvdlg, I would be open to add support for it in https://github.com/kevva/argvments (which uses minimist). Planning to do a PR on meow to use it.

[pvdlg]

As https://github.com/kevva/argvments uses minimist internally, wouldn't the problem be the same?

[pvdlg]

Even if we can always find workaround minimist, maybe that's a good occasion to stop relying on it as it's not maintained anymore.

[kevva]

I'll just handle it after I've parsed them with minimist.

Even if we can always find workaround minimist, maybe that's a good occasion to stop relying on it as it's not maintained anymore.

Maybe...

[pvdlg]

A workaround would be to set the default property of boolean flags to null and delete the null prop from the result option object.

prettier: {
	type: 'boolean',
	default: null
}

then

const {pickBy} = require('lodash');
const opts = pickBy(cli.flags, value => value !== null))

This default: null + filtering can be done in XO or in meow.

Still we can have discuss and decide if we want to move away from a minimist based solution or not, and what would be the best solution.

[pvdlg]

I tried to implement the workaround mentioned above in meow but unfortunately it doesn't work due to another minimist bug that seems related to alias and default props.

minimist(['-f'], {boolean: ['foo'], alias: {f: 'foo'}, default: {foo: null}});
// => {_: [], foo: true, f: [null, true]}
// Should be {_: [], foo: true, f:  true}

minimist(['--foo'], {boolean: ['foo'], alias: {f: 'foo'}, default: {foo: null}});
// => {_: [], foo: true, f: [null, true]}
// Should be {_: [], foo: true, f:  true}

Even by setting default for both the flag and it's alias cause the issue:

minimist(['-f'], {boolean: ['foo'], alias: {f: 'foo'}, default:{foo: null, f: null}})
//=> {_: [], foo: true, f: [null, true]}

For info:

yargsParser(['--foo'], {boolean: ['foo'], alias: {f: 'foo'}, default:{foo: null}});
// => {_: [], foo: true, f: true}

yargsParser(['-f'], {boolean: ['foo'], alias: {f: 'foo'}, default:{foo: null}});
// => {_: [], foo: true, f: true}

[pvdlg]

I opened sindresorhus/meow#77 as a potential fix, that relies on yargs-parser.

I can also quickly create a PR for XO that would use yargs directly, to see how the code would look like.

[sindresorhus]

I opened sindresorhus/meow#77 as a potential, that relies on yargs-parser.

I like it.

I can also quickly create a PR for XO that would use yargs directly, to see how the code would look like.

Sure. Meow was never meant for huge CLIs like XO. I just made it to abstract common things in the small CLIs I make. Yargs is much better suited for our needs in XO.

I still want the sindresorhus/meow#77 change in Meow though.

[pvdlg]

Ok, so you have the PR opened in meow. We can improve it in another PR to add the other yargs-parser options (besides alias, string, default, boolean) if you'd like.

I'll open a PR for XO with yargs tonight.

[sindresorhus]

We can improve it in another PR to add the other yargs-parser options (besides alias, string, default, boolean) if you'd like.

That would be amazing.

[pvdlg]

With sindresorhus/meow#77 this issue can be solved by setting the boolean flag default to undefined or by using booleanDefault: undefined.

We can still migrate to yargs if we need some of its features, but we will have to filter out undefined values due to yargs/yargs#1071.

The possible yargs features that could be useful:

• Auto-generation of the help message => slightly simpler code for us
• Stricter validation => Display an error if the user enter un unknown option
• Easier way to set multi-value flags with array type => can be either xo --env browser jquery or xo --env browser --env jquery while currently only the second forms works
• Additional type like number or count but we don't need them at the moment

[sindresorhus]

sindresorhus/meow#77 is now available in Meow 5.0.0.