util: parseArgs() treats a `-` inside a short option group as the `--` terminator

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@yohannesjoya is already working on this.

Since Nov 3, 2026.

  • #67228 by @yohannesjoya — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
75/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
javascript, nodejs
Domain
cli

Research direction

Start with argsToTokens() in lib/internal/util/parse_args/parse_args.js, where a short option group like -a-b is expanded and pushed back onto the argument list. Check how the loop orders the arg === '--' test against the group counter, so a synthesized -- is not treated as the real terminator. Run the reproduction from the issue with strict and non-strict modes, plus tokens: true, and confirm -a-b yields an unknown-option error and each token's index matches its source argument. Done when the existing parseArgs tests pass and new cases cover -a-b and -a-.

Written by the indexing model from the issue text.

Description

Version

v28.0.0-pre (main, d2812af0), also v22.20.0

Platform

Linux 7.0.0-38-generic x86_64

Subsystem

util

What steps will reproduce the bug?
const { parseArgs } = require('node:util');

const options = { a: { type: 'boolean' }, b: { type: 'boolean' } };

// Non-strict, with tokens.
const args = ['-a-b', 'pos'];
const { values, positionals, tokens } = parseArgs({
  args, options, strict: false, allowPositionals: true, tokens: true,
});
console.log(values, positionals);
for (const token of tokens) {
  console.log(token, '-> args[index] =', args[token.index]);
}

// Strict.
for (const arg of ['-a-b', '-a-']) {
  try {
    parseArgs({ args: [arg], options });
    console.log(arg, 'ok');
  } catch (err) {
    console.log(arg, err.code, '-', err.message);
  }
}
How often does it reproduce? Is there a required condition?

Every time. Needs a - character inside a short option group, for example -a-b or -a-.

What is the expected behavior?

- is not a valid option character, so -a-b should be reported the same way as any other unknown short option in a group (compare -ar with r unknown). In strict mode that is ERR_PARSE_ARGS_UNKNOWN_OPTION. With tokens: true, every token's index should point at the argument it came from, as the docs say: "the source argument for a token is args[token.index]".

What do you see instead?
[Object: null prototype] { a: true } [ '-b', 'pos' ]
{ kind: 'option', name: 'a', rawName: '-a', index: 0, value: undefined, inlineValue: undefined } -> args[index] = -a-b
{ kind: 'option-terminator', index: 0 } -> args[index] = -a-b
{ kind: 'positional', index: 1, value: '-b' } -> args[index] = pos
{ kind: 'positional', index: 2, value: 'pos' } -> args[index] = undefined
-a-b ERR_PARSE_ARGS_UNEXPECTED_POSITIONAL - Unexpected argument '-b'. This command does not take positional arguments
-a- ok
  • -b becomes a positional instead of an option.
  • An option-terminator token appears although the user never passed --.
  • The positional indexes are shifted by one, so args[token.index] is the wrong argument or undefined.
  • In strict mode -a-b reports a misleading unexpected-positional error, and -a- is accepted silently.
Additional information

argsToTokens() in lib/internal/util/parse_args/parse_args.js expands a short option group -a-b into -a, --, -b and pushes them back onto the argument list. The loop then checks arg === '--' before it looks at whether the argument came from a group, so the synthesized -- is handled as the real terminator. The group counter (groupCount) already knows the argument was expanded.

For comparison, getopt(3) reports -a-b as invalid option -- '-'.

I have a small fix with tests and can open a PR.

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