Flags undefined in tokenize

[isglass]

Hi,

Can't reproduce it properly, but sometimes when using FileHighlighter plugin we get flags undefined in tokenize. Which leads to RegExp exception, it tries undefinedg.

Since I can't reproduce when debugging i propose the following:

var flags = pattern.pattern.toString().match(/[imuy]*$/)[0];
pattern.pattern = RegExp(pattern.pattern.source, flags + "g");

Replaced with:

var flags = pattern.pattern.toString().match(/[imuy]*$/)[0];
pattern.pattern = RegExp(pattern.pattern.source, (flags || "") + "g");

Regards,
Johan

[zeitgeist87]

Hi @isglass,

Thanks for reporting this. I cannot see how flags could become undefined. The expression 'anystring'.match(/[imuy]*$/)[0]; returns at least an empty string for any input string.

'xxx'.match(/[imuy]*$/)[0];
''.match(/[imuy]*$/)[0];
RegExp('', '').toString().match(/[imuy]*$/)[0];

And if pattern.pattern.toString() would somehow return undefined, then you would get an error right there.

The following is the only way I can think of, that would cause this bug:

RegExp.prototype.toString = function() {
    return {
        match: function() { return [] }
    }
}

I think we should get to the root of this problem. Could you provide more details for this bug? What browser did you use? Maybe a simple online demo that reproduces it?

Thanks!

[zeitgeist87]

For flags to be undefined, match() has to return an empty array, which cannot happen under normal circumstances:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/match

An Array containing the entire match result and any parentheses-captured matched results, or null if there were no matches.

[isglass]

Hi @zeitgeist87 ,

Unfortunately I can't reproduce it, have only noticed it in our "visitor-exception-logs" over the last couple of days. All I have got is their user agent:

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.80 Safari/537.36

And a stack trace:

new RegExp  @ (native):
RegExp  @ (native):
Object._self.Prism.tokenize @ prism.js:3
Object._self.Prism.highlight    @ prism.js:3
Object._self.Prism.highlightElement @ prism.js:3
XMLHttpRequest.i.onreadystatechange @ prism.js:8

And exception message:

Invalid flags supplied to RegExp constructor 'undefinedg'

[zeitgeist87]

The user-agent would suggest, that it is a 64bit Linux system running Chromium 47.0.2526.80 which is over a year old now. Do all these users have the same user-agent? Could it be some kind of crawler that uses a fake user-agent?

The only way for flags to become undefined is if you change either the prototype of RegExp or String. At least as far as I can see. I don't think we will add these changes if you cannot reproduce the bug, or show a plausible way how flags can be undefined.

Maybe you could add some debug code to your site that provides more information:

if (flags === undefined) {
    console.log(pattern, pattern.pattern, pattern.pattern.toString(), pattern.pattern.toString().match(/[imuy]*$/));
}

[LeaVerou]

What other scripts are you using? Perhaps one of them is overwriting native methods, and making match() return an empty array?

[Golmote]

Please reopen if you can provide more information regarding this issue.