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

'use strict';
var createNonEnumerableProperty = require('../internals/create-non-enumerable-property');
var redefine = require('../internals/redefine');
var fails = require('../internals/fails');
var wellKnownSymbol = require('../internals/well-known-symbol');
var regexpExec = require('../internals/regexp-exec');

var SPECIES = wellKnownSymbol('species');

var REPLACE_SUPPORTS_NAMED_GROUPS = !fails(function () {
  // #replace needs built-in support for named groups.
  // #match works fine because it just return the exec results, even if it has
  // a "grops" property.
  var re = /./;
  re.exec = function () {
    var result = [];
    result.groups = { a: '7' };
    return result;
  };
  return ''.replace(re, '$<a>') !== '7';
});

// Chrome 51 has a buggy "split" implementation when RegExp#exec !== nativeExec
// Weex JS has frozen built-in prototypes, so use try / catch wrapper
var SPLIT_WORKS_WITH_OVERWRITTEN_EXEC = !fails(function () {
  var re = /(?:)/;
  var originalExec = re.exec;
  re.exec = function () { return originalExec.apply(this, arguments); };
  var result = 'ab'.split(re);
  return result.length !== 2 || result[0] !== 'a' || result[1] !== 'b';
});

module.exports = function (KEY, length, exec, sham) {
  var SYMBOL = wellKnownSymbol(KEY);

  var DELEGATES_TO_SYMBOL = !fails(function () {
    // String methods call symbol-named RegEp 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 ||
    (KEY === 'replace' && !REPLACE_SUPPORTS_NAMED_GROUPS) ||
    (KEY === 'split' && !SPLIT_WORKS_WITH_OVERWRITTEN_EXEC)
  ) {
    var nativeRegExpMethod = /./[SYMBOL];
    var methods = exec(SYMBOL, ''[KEY], function (nativeMethod, regexp, str, arg2, forceStringMethod) {
      if (regexp.exec === regexpExec) {
        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: nativeRegExpMethod.call(regexp, str, arg2) };
        }
        return { done: true, value: nativeMethod.call(str, regexp, arg2) };
      }
      return { done: false };
    });
    var stringMethod = methods[0];
    var regexMethod = methods[1];

    redefine(String.prototype, KEY, stringMethod);
    redefine(RegExp.prototype, SYMBOL, length == 2
      // 21.2.5.8 RegExp.prototype[@@replace](string, replaceValue)
      // 21.2.5.11 RegExp.prototype[@@split](string, limit)
      ? function (string, arg) { return regexMethod.call(string, this, arg); }
      // 21.2.5.6 RegExp.prototype[@@match](string)
      // 21.2.5.9 RegExp.prototype[@@search](string)
      : function (string) { return regexMethod.call(string, this); }
    );
    if (sham) createNonEnumerableProperty(RegExp.prototype[SYMBOL], 'sham', true);
  }
};