Avoid changes to object affecting the result of a match function.

lodash.js

@@ -8524,14 +8524,17 @@
      * // => { 'name': 'barney', 'age': 36 }
      */
     function matches(source) {
-      var props = keys(source),
-          propsLength = props.length,
-          key = props[0],
-          value = propsLength && source[key];
+      var keyVals = pairs(source),
+          keyValsLength = keyVals.length;
 
+      if (keyValsLength) {
+        var keyVal = keyVals[0],
+            key = keyVal[0],
+            value = keyVal[1];
+      }
       // fast path the common case of providing an object with a single
       // property containing a primitive value
-      if (propsLength == 1 && value === value && !isObject(value)) {
+      if (keyValsLength == 1 && value === value && !isObject(value)) {
         return function(object) {
           if (object == null) {
             return false;
@@ -8542,14 +8545,15 @@
         };
       }
       return function(object) {
-        var length = propsLength;
+        var length = keyValsLength;
         if (length && object == null) {
           return false;
         }
         while (length--) {
-          var key = props[length];
+          keyVal = keyVals[length];
+          key = keyVal[0];
           if (!(hasOwnProperty.call(object, key) &&
-                baseIsEqual(source[key], object[key], null, true))) {
+                baseIsEqual(keyVal[1], object[key], null, true))) {
             return false;
           }
         }

test/test.js

@@ -6689,6 +6689,22 @@
       strictEqual(matches(otherObject), false);
     });
 
+    test('should not change match behavior if `source` is augmented', 6, function() {
+      _.each([{ 'a': 1 }, { 'a': 1, 'b': 2 }], function(source) {
+        var object = _.clone(source),
+            matches = _.matches(source);
+
+        strictEqual(matches(object), true);
+
+        source.a = 2;
+        source.b = 1;
+        source.c = 3;
+
+        strictEqual(matches(object), true);
+        strictEqual(matches(source), false);
+      });
+    });
+
     test('should return `true` when comparing an empty `source`', 1, function() {
       var object = { 'a': 1 },
           expected = _.map(empties, _.constant(true));