Add new type 'number'

[maxrimue]

This adds a new type number.

A number-type option has the following special behaviour:

• If the flag itself is not provided, its value will default to undefined, unless defined otherwise via .default()
• If no number is provided as a value, its value will default to NaN (that means, if Number() isn't capable of coercing the value to a number primitive)

Note: Where should I implement the logic for checking if the given value is a number? I thought of the following code:

if (typeof x === 'number') {
  return x
} else {
  return Number(x) // Will return NaN if x is not coercible to a number
}

I am aware of isNumber(), however, it only returns true if the option parse-numbers equals false, which is obviously not related to the number-type. What do folks think?

[bcoe]

@nexdrew what are your thoughts about defaulting a number to undefined ... but one could also argue for NaN or 0.

[lrlna]

defaulting to undefined is better imo. Dealing with NaN has always been a pain in the butt in my experience.

[bcoe]

@maxrimue this is looking good so far, need any help getting tests passing?

[bcoe]

I think you can get rid of this check, it won't actually do anything, instead update:

https://github.com/yargs/yargs-parser/blob/master/index.js#L315

To be something like:

var value = val
if (!checkAllAliases(key, flags.strings)) {
  if (isNumber(val) || checkAllAliases(key, flags.numbers)) value = Number(val)
}

[lrlna]

@bcoe @maxrimue got this going so far:

    if (!checkAllAliases(key, flags.strings)) {
      if (isNumber(val)) value = Number(val)
      if (!isNumber(val) && checkAllAliases(key, flags.numbers) && !isUndefined(val)) value = NaN
    }

[lrlna]

@maxrimue sorry -- I can't push to your branch for some reason!! I am opening a new Pull Request #7 to add that line of code.