avoiding infinite loop in String#gsub when there is a zero length match

Author: rlineweaver

src/prototype/lang/string.js

@@ -100,7 +100,8 @@ Object.extend(String.prototype, (function() {
     }
 
     while (source.length > 0) {
-      if (match = source.match(pattern)) {
+      match = source.match(pattern)
+      if (match && match[0].length > 0) {
         result += source.slice(0, match.index);
         result += String.interpret(replacement(match));
         source  = source.slice(match.index + match[0].length);

test/unit/string_test.js

@@ -66,7 +66,6 @@ new Test.Unit.Runner({
 
   testGsubWithTroublesomeCharacters: function() {
     this.assertEqual('ab', 'a|b'.gsub('|', ''));
-    //'ab'.gsub('', ''); // freeze
     this.assertEqual('ab', 'ab(?:)'.gsub('(?:)', ''));
     this.assertEqual('ab', 'ab()'.gsub('()', ''));
     this.assertEqual('ab', 'ab'.gsub('^', ''));
@@ -77,6 +76,12 @@ new Test.Unit.Runner({
     this.assertEqual('ab', 'a.b'.gsub('.', ''));
   },  
 
+  testGsubWithZeroLengthMatch: function() {
+    this.assertEqual('ab', 'ab'.gsub('', ''));
+    this.assertEqual('a', 'a'.gsub(/b*/, 'c'));
+    this.assertEqual('abc', 'abc'.gsub(/b{0}/, ''));
+  },
+  
   testSubWithReplacementFunction: function() {
     var source = 'foo boo boz';