flags: Skip parsing numeric-looking argument with no option

[sntran]

Is your feature request related to a problem? Please describe.

When parsing numeric-looking arguments which is not a flag, they are parsed as number. There are cases which it is not desired to do so. For example:

// $ deno run example.ts 000000 '000000'
import { parse } from "https://deno.land/[email protected]/flags/mod.ts";
console.dir(parse(Deno.args));
// output: { _: [ 0, 0 ] }

Describe the solution you'd like

There is string option to indicate argument names to be treated as string instead, but since the above argument is not a flag, it can't be specified with string option. It would be nice to have another option to indicate such argument.

Describe alternatives you've considered

Setting - as string works, but it skips number parsing all arguments in -. I can't think of another way.

[jgrunik]

I too have this issue.
BigInts are being cast to ints.
I see no workaround.

[kamilogorek]

One possible workaround would be to check whether serializing/deserializing will yield the same result. If so, then parse it. Otherwise, leave it as a string to be handled by the end user.

function shouldParseAsNumber(val: string): boolean {
  if (!isNumber(val)) {
    return val;
  }

  return Number(val).toString() === val;
}

shouldParseAsNumber('0'); // true
shouldParseAsNumber('7'); // true
shouldParseAsNumber('1337'); // true
shouldParseAsNumber('00'); // false
shouldParseAsNumber('007'); // false

As for BigInt, it'd require a change to isNumber checking for the n prefix, however, as this is treated as a string, it can already be handled by the user just fine.

[cmitsakis]

I was bitten by this unexpected behavior when I tried to parse a big number that couldn't be represented accurately as a number. I believe all non-flag arguments should be strings. No reason to try to be clever. The users should explicitly parse them to the type they want.

[lino-levan]

I have to agree. I think they should always be parsed as strings, would hate to introduce footguns. This is a breaking change though. How should we go about doing it?