Fix a bug where we recreated sync filters

Fix the object comparison used for client filters (JSON.stringify is
non-deterministic)

lib/utils.js

@@ -246,6 +246,92 @@ module.exports.deepCopy = function(obj) {
     return JSON.parse(JSON.stringify(obj));
 };
 
+/**
+ * Compare two objects for equality. The objects MUST NOT have circular references.
+ *
+ * @param {Object} x The first object to compare.
+ * @param {Object} y The second object to compare.
+ *
+ * @return {boolean} true if the two objects are equal
+ */
+var deepCompare = module.exports.deepCompare = function(x, y) {
+    // Inspired by
+    // http://stackoverflow.com/questions/1068834/object-comparison-in-javascript#1144249
+
+    // Compare primitives and functions.
+    // Also check if both arguments link to the same object.
+    if (x === y) {
+        return true;
+    }
+
+    if (typeof x !== typeof y) {
+        return false;
+    }
+
+    // special-case NaN (since NaN !== NaN)
+    if (typeof x === 'number' && isNaN(x) && isNaN(y)) {
+         return true;
+    }
+
+    // special-case null (since typeof null == 'object', but null.constructor
+    // throws)
+    if (x === null || y === null) {
+        return x === y;
+    }
+
+    // everything else is either an unequal primitive, or an object
+    if (!(x instanceof Object)) {
+        return false;
+    }
+
+    // check they are the same type of object
+    if (x.constructor !== y.constructor || x.prototype !== y.prototype) {
+        return false;
+    }
+
+    // special-casing for some special types of object
+    if (x instanceof RegExp || x instanceof Date) {
+        return x.toString() === y.toString();
+    }
+
+    // the object algorithm works for Array, but it's sub-optimal.
+    if (x instanceof Array) {
+        if (x.length !== y.length) {
+            return false;
+        }
+
+        for (var i = 0; i < x.length; i++) {
+            if (deepCompare(x[i], y[i])) {
+                return false;
+            }
+        }
+    } else {
+        // disable jshint "The body of a for in should be wrapped in an if
+        // statement"
+        /* jshint -W089 */
+
+        // check that all of y's direct keys are in x
+        var p;
+        for (p in y) {
+            if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
+                return false;
+            }
+        }
+
+        // finally, compare each of x's keys with y
+        for (p in y) {
+            if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
+                return false;
+            }
+            if (!deepCompare(x[p], y[p])) {
+                return false;
+            }
+        }
+    }
+    /* jshint +W089 */
+    return true;
+};
+
 
 /**
  * Run polyfills to add Array.map and Array.filter if they are missing.