[REGEX] Support duplicate named capturing groups that are in different disjunction alternatives

[coderfin]

Goals

Support regular expressions with duplicate named capturing groups that are in different disjunction alternatives.

Non-Goals

No response

Background

Links

• Browser support
  • https://caniuse.com/mdn-javascript_regular_expressions_named_capturing_group_duplicate_named_capturing_groups
• MDN
  • https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Named_capturing_group
    • See paragraph starting with This restriction is relaxed if...
• Ecma TC39
  • https://github.com/tc39/proposal-duplicate-named-capturing-groups
• Babel
  • https://babeljs.io/docs/babel-plugin-transform-duplicate-named-capturing-groups-regex

Example

/^(?:\/(?<locale>en)$|\/(?<locale>en)\/|\/(?<locale>es)$|\/(?<locale>es)\/|\/(?<locale>fr)$|\/(?<locale>fr)\/)/gi.exec('/fr/about')

Regex in NextJS results in an error (browser - Chrome 125):

Regex run in the browser console gives a working result (browser - Chrome 125):

Alternative

You can use and perform various operations on the index values (0-6 in the working example above).

Proposal

This feature could initially be supported by setting an experimental option in next.config.mjs or some other "opt-in" mechanism. Perhaps the browserlist could be used or babel or SWC.