core-js/internals/fix-regexp-well-known-symbol-logic.js

'use strict';
// TODO: Remove from `core-js@4` since it's moved to entry points
require('../modules/es.regexp.exec');
var call = require('../internals/function-call');
var defineBuiltIn = require('../internals/define-built-in');
var regexpExec = require('../internals/regexp-exec');
var fails = require('../internals/fails');
var wellKnownSymbol = require('../internals/well-known-symbol');
var createNonEnumerableProperty = require('../internals/create-non-enumerable-property');

var SPECIES = wellKnownSymbol('species');
var RegExpPrototype = RegExp.prototype;

module.exports = function (KEY, exec, FORCED, SHAM) {
  var SYMBOL = wellKnownSymbol(KEY);

  var DELEGATES_TO_SYMBOL = !fails(function () {
    // String methods call symbol-named RegExp methods
    var O = {};
    O[SYMBOL] = function () { return 7; };
    return ''[KEY](O) !== 7;
  });

  var DELEGATES_TO_EXEC = DELEGATES_TO_SYMBOL && !fails(function () {
    // Symbol-named RegExp methods call .exec
    var execCalled = false;
    var re = /a/;

    if (KEY === 'split') {
      // We can't use real regex here since it causes deoptimization
      // and serious performance degradation in V8
      // https://github.com/zloirock/core-js/issues/306
      re = {};
      // RegExp[@@split] doesn't call the regex's exec method, but first creates
      // a new one. We need to return the patched regex when creating the new one.
      re.constructor = {};
      re.constructor[SPECIES] = function () { return re; };
      re.flags = '';
      re[SYMBOL] = /./[SYMBOL];
    }

    re.exec = function () {
      execCalled = true;
      return null;
    };

    re[SYMBOL]('');
    return !execCalled;
  });

  if (
    !DELEGATES_TO_SYMBOL ||
    !DELEGATES_TO_EXEC ||
    FORCED
  ) {
    var nativeRegExpMethod = /./[SYMBOL];
    var methods = exec(SYMBOL, ''[KEY], function (nativeMethod, regexp, str, arg2, forceStringMethod) {
      var $exec = regexp.exec;
      if ($exec === regexpExec || $exec === RegExpPrototype.exec) {
        if (DELEGATES_TO_SYMBOL && !forceStringMethod) {
          // The native String method already delegates to @@method (this
          // polyfilled function), leasing to infinite recursion.
          // We avoid it by directly calling the native @@method method.
          return { done: true, value: call(nativeRegExpMethod, regexp, str, arg2) };
        }
        return { done: true, value: call(nativeMethod, str, regexp, arg2) };
      }
      return { done: false };
    });

    defineBuiltIn(String.prototype, KEY, methods[0]);
    defineBuiltIn(RegExpPrototype, SYMBOL, methods[1]);
  }

  if (SHAM) createNonEnumerableProperty(RegExpPrototype[SYMBOL], 'sham', true);
};