utils: Simplify URL regex to only support one layer of parentheses

The author of the original URL-matching regex warns[0] that the pattern may
cause certain regex engines to lock up with certain input, namely patterns
that contain parentheses. It turns out SpiderMonkey is affected, but rather
than switching to the author's improved version (that is still crazy), sim-
plify the pattern a bit by removing support for nested parentheses in URLs.
Even a single pair of parentheses is extremely rare, so this is unlikely to
make a noticeable difference (other than not locking up SpiderMonkey of
course) ...

[0] http://daringfireball.net/2010/07/improved_regex_for_matching_urls

js/misc/util.js

@@ -17,7 +17,7 @@ const Params = imports.misc.params;
 var SCROLL_TIME = 0.1;
 
 // http://daringfireball.net/2010/07/improved_regex_for_matching_urls
-const _balancedParens = '\\((?:[^\\s()<>]+|(?:\\(?:[^\\s()<>]+\\)))*\\)';
+const _balancedParens = '\\([^\\s()<>]+\\)';
 const _leadingJunk = '[\\s`(\\[{\'\\"<\u00AB\u201C\u2018]';
 const _notTrailingJunk = '[^\\s`!()\\[\\]{};:\'\\".,<>?\u00AB\u00BB\u201C\u201D\u2018\u2019]';
 

tests/unit/url.js

@@ -38,6 +38,10 @@ const tests = [
       output: [ { url: 'http://www.gnome.org:99/port', pos: 10 } ] },
     { input: 'This is an ftp://www.gnome.org/ test.',
       output: [ { url: 'ftp://www.gnome.org/', pos: 11 } ] },
+    { input: 'https://www.gnome.org/(some_url,_with_very_unusual_characters)',
+      output: [ { url: 'https://www.gnome.org/(some_url,_with_very_unusual_characters)', pos: 0 } ] },
+    { input: 'https://www.gnome.org/(some_url_with_unbalanced_parenthesis',
+      output: [ { url: 'https://www.gnome.org/', pos: 0 } ] },
 
     { input: 'Visit http://www.gnome.org/ and http://developer.gnome.org',
       output: [ { url: 'http://www.gnome.org/', pos: 6 },