Atom hang with 100% cpu when regex engine does catastrophic backtracking

[jeancroy]

Buffer: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Search: [A-Z0-9]+([A-Z0-9._%+-]*)+@[A-Z0-9.-]+\.[A-Z]{2,4}
Options: Regex, Case insensitive, No word Boundary.

Search make atom freeze with 100% CPU, no decoration or large buffer involved. After some time, 'editor is unresponsive' popup appears.

Example regex is a real life (bad) email regex found on stackoverflow. Problem start while trying to match @. Because search can't find @, regex backtrack. The problem then is ([]*)+ pattern which basically mean: any amount of group containing any amount of character. And there's ton of permutation of that ! Nevertheless regex engine will examine every on of them just in case one permutation will free up a @.

Maybe the suggestion to use a separate thread for searching is not all bad.

One interesting bit of information is that Atom use oniguruma for syntax coloring, which support async search with callback. This might be a relatively cheap route for implementing search in a separate thread.

Alternative one could be to try to sanitize the regex.

[alexchandel]

This would be fixed by #571, since oniguruma handles this much better.