RegExp syntax error in IE when using Google Closure Compiler

[Grundik]

There are several places in code, where are workarounds for IE misunderstanding of some regexp flags:

• internals/regexp-sticky-helpers.js for flag 'y';
• internals/regexp-unsupported-dot-all.js for flag 's';
• internals/regexp-unsupported-ncg.js for flag 'g'.

Workarounds are like:

// babel-minify transpiles RegExp('a', 'y') -> /a/y and it causes SyntaxError,
var RE = function (s, f) {
  return RegExp(s, f);
};

exports.UNSUPPORTED_Y = fails(function () {
  var re = RE('a', 'y');
  re.lastIndex = 2;
  return re.exec('abcd') != null;
});

and

module.exports = fails(function () {
  // babel-minify transpiles RegExp('.', 's') -> /./s and it causes SyntaxError
  var re = RegExp('.', (typeof '').charAt(0));
  return !(re.dotAll && re.exec('\n') && re.flags === 's');
});

That could work fine with Babel, but Google Closure Compiler cannot be fooled like that. It understands such tricks, and still compiles code into failing regexps.

That could be prevented by using "@noinline" flag, like this:

// babel-minify transpiles RegExp('a', 'y') -> /a/y and it causes SyntaxError,
/** @noinline */
var RE = function (s, f) {
  return RegExp(s, f);
};

in all 3 places.

[zloirock]

Thanks for the issue. However, such directives-comments will not work if you will pass already minified core-js with removed comments to Closure Compiler - that confuses me.

[Grundik]

Yes, thats a small problem. But if one uses google closure compiler, there are no point to compile minified files. Its better to use source files, to get useful source maps.

[zloirock]

Could you try to add

var RegExp = require('../internals/global').RegExp;

at the top of those files?

[Grundik]

Yes, that works too, compiles into

var d=a(17).RegExp;b.UNSUPPORTED_Y=c(function(){var e=d("a","y"); .... }

with SIMPLE compilation level.