@babel/plugin-proposal-duplicate-named-capturing-groups-regex: support dynamically created regular expressions

[rauschma]

💻

• Would you like to work on this feature?

What problem are you trying to solve?

The plugin works for RegExp literals but not for regular expressions created via new RegExp().

Describe the solution you'd like

FWIW: I created the following (quick and very dirty) workaround: I replace new RegExp with new RegExpX – which invokes the class shown below. The solution I’d like would be cleaner than that.

class RegExpX {
  constructor(str, flags) {
    const RE = /(?<!\\)\((\?<(?<name>[^<>]+)>)?/g;
    let parenCounter = 0;
    const groupNameToGroupNumbers = new Map();
    str = str.replaceAll(
      RE,
      (all, ...args) => {
        const groups = args.pop();
        parenCounter++;
        if (groups.name) {
          let groupNumbers = groupNameToGroupNumbers.get(groups.name);
          if (groupNumbers === undefined) {
            groupNumbers = [];
            groupNameToGroupNumbers.set(groups.name, groupNumbers);
          }
          groupNumbers.push(parenCounter);
          // It’s in the Map, only its group number matters now
          return `(`; // avoid any name clashes
        }
        return all;
      }
    );
    // Override what the constructor would normally return:
    return _wrapRegExp(
      new RegExp(str, flags),
      Object.fromEntries(groupNameToGroupNumbers)
    );
  }
}

Describe alternatives you've considered

None

Documentation, Adoption, Migration Strategy

No response

[babel-bot]

Hey @rauschma! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite.

[liuxingbaoyu]

zloirock/core-js@913625f
Have you enabled corejs? It seems they already support it.

[rauschma]

Thanks! I tried both of the following import statements:

import 'core-js/actual/regexp/constructor.js';
import 'core-js/actual/index.js';

But both failed as follows:

SyntaxError: Invalid regular expression:
/^(?<year>[0-9]{4})-(?<month>[0-9]{2})|(?<month>[0-9]{2})\/(?<year>[0-9]{4})$/:
Duplicate capture group name

I can create an issue for core-js, but it may make sense to document that the Babel plugin only handles RegExp literals.