fix ie8 splice bug

lib/ace/lib/es5-shim.js

@@ -176,17 +176,95 @@ if ((supportsAccessors = owns(prototypeOfObject, "__defineGetter__"))) {
 // [bugfix, ielt9, old browsers]
 // IE < 9 bug: [1,2].splice(0).join("") == "" but should be "12"
 if ([1,2].splice(0).length != 2) {
-    var array_splice = Array.prototype.splice;
-    Array.prototype.splice = function(start, deleteCount) {
-        if (!arguments.length) {
-            return [];
-        } else {
-            return array_splice.apply(this, [
-                start === void 0 ? 0 : start,
-                deleteCount === void 0 ? (this.length - start) : deleteCount
-            ].concat(slice.call(arguments, 2)))
+    if(function() { // test IE < 9 to splice bug - see issue #138
+        function makeArray(l) {
+            var a = new Array(l+2);
+            a[0] = a[1] = 0;
+            return a;
         }
-    };
+        var array = [], lengthBefore;
+        
+        array.splice.apply(array, makeArray(20));
+        array.splice.apply(array, makeArray(26));
+
+        lengthBefore = array.length; //46
+        array.splice(5, 0, "XXX"); // add one element
+
+        lengthBefore + 1 == array.length
+
+        if (lengthBefore + 1 == array.length) {
+            return true;// has right splice implementation without bugs
+        }
+        // else {
+        // IE8 bug
+        // }
+    }()) {//IE 6/7
+        var array_splice = Array.prototype.splice;
+        Array.prototype.splice = function(start, deleteCount) {
+            if (!arguments.length) {
+                return [];
+            } else {
+                return array_splice.apply(this, [
+                    start === void 0 ? 0 : start,
+                    deleteCount === void 0 ? (this.length - start) : deleteCount
+                ].concat(slice.call(arguments, 2)))
+            }
+        };
+    } else {//IE8
+        // taken from http://docs.sencha.com/ext-js/4-1/source/Array2.html
+        Array.prototype.splice = function(pos, removeCount){
+            var length = this.length;
+            if (pos > 0) {
+                if (pos > length)
+                    pos = length;
+            } else if (pos == void 0) {
+                pos = 0;
+            } else if (pos < 0) {
+                pos = Math.max(length + pos, 0);
+            }
+
+            if (!(pos+removeCount < length))
+                removeCount = length - pos;
+
+            var removed = this.slice(pos, pos+removeCount);
+            var insert = slice.call(arguments, 2);
+            var add = insert.length;            
+
+            // we try to use Array.push when we can for efficiency...
+            if (pos === length) {
+                if (add) {
+                    this.push.apply(this, insert);
+                }
+            } else {
+                var remove = Math.min(removeCount, length - pos);
+                var tailOldPos = pos + remove;
+                var tailNewPos = tailOldPos + add - remove;
+                var tailCount = length - tailOldPos;
+                var lengthAfterRemove = length - remove;
+
+                if (tailNewPos < tailOldPos) { // case A
+                    for (var i = 0; i < tailCount; ++i) {
+                        this[tailNewPos+i] = this[tailOldPos+i];
+                    }
+                } else if (tailNewPos > tailOldPos) { // case B
+                    for (i = tailCount; i--; ) {
+                        this[tailNewPos+i] = this[tailOldPos+i];
+                    }
+                } // else, add == remove (nothing to do)
+
+                if (add && pos === lengthAfterRemove) {
+                    this.length = lengthAfterRemove; // truncate array
+                    this.push.apply(this, insert);
+                } else {
+                    this.length = lengthAfterRemove + add; // reserves space
+                    for (i = 0; i < add; ++i) {
+                        this[pos+i] = insert[i];
+                    }
+                }
+            }
+            return removed;
+        };
+    }
 }
 
 // ES5 15.4.3.2