[naveentehrpariya]

Fixes #418.

The bug

An option configured with narg: 0 takes no arguments, so passing it is a switch — the existing test should not use next value for boolean/number/string configured with zero narg asserts exactly that: bool → true, nr → undefined, str → ''.

But eatNargs produces that value through defaultValue(), which returns the configured default for any option that is not declared boolean or count:

function defaultValue (key: string) {
  if (!checkAllAliases(key, flags.bools) &&
      !checkAllAliases(key, flags.counts) &&
      `${key}` in defaults) {
    return defaults[key]
  }
  ...

So adding a default of false makes the option parse as false even when it is given on the command line:

parser(['-a', 'hello', '-b', 'world'], {
  narg: { a: 1, b: 0 },
  default: { b: false },
  alias: { blah: ['b', 'bl'] }
})

// actual
{ _: ['world'], a: 'hello', b: false, blah: false, bl: false }
// expected
{ _: ['world'], a: 'hello', b: true, blah: true, bl: true }

Declaring the option boolean: true works, which is why this only shows up for options that use narg to accept either a value or no value at all.

The fix

eatNargs now takes the value implied by the option's type directly, instead of going through defaultValue(). A default is the value an option takes when it is absent, so it should not be consulted for an option that was given.

Tests

• An option with narg: 0 and a default of false parses as true (along with its aliases) when it is passed. Fails on main with expected … to have property 'b' of true, but got false.
• The default still applies when the option is not passed.

npm test is 364 passing / 0 failing, npm run test:typescript 20 passing, npm run check clean.

[shadowspawn]

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