Multiple arguments are incremented if they are equal to 1.

Yargs version used: 18.0.0

How to reproduce

const parser = require('yargs-parser')
parser("-x 3 -x 1")

returns

{ _: [], x: 4 }

i.e., it wrongfully calculated 3 + 1 = 4.

Expected would be

{ _: [], x: [ 3, 1 ] }

The option "duplicate-arguments-array": false still results in 4.

If the order is changed, i.e.,

const parser = require('yargs-parser')
parser("-x 1 -x 3")

then the result is correct.

Bug Cause

The increment happens in yargs-parser.ts -> setKey at this code line:

if (value === increment()) {
   o[key] = increment(o[key])
} 

increment() === 1, i.e., it increments o[key] each time we have any argument which equals to 1.

The increment function has a comment on top stating that it "should only be called when a count is given as an arg". Obviously, we have a number and not a count here.

Workaround

A workaround in yargs/yargs consists in setting type="string".

Start in lib/yargs-parser.ts at setKey, around the linked line, and inspect how increment() is selected when repeated values are parsed. Reproduce with parser("-x 3 -x 1") and the duplicate-arguments-array option; done means repeated numeric values produce [3, 1] rather than 4 while count arguments retain their existing behavior.