Clarify browsers affected by nonEnumArgs and reduce code around hasEnumPrototype.

Former-commit-id: 587f755332accbca26dc1eb357a66d4f898aad88

lodash.js

@@ -85,7 +85,6 @@
       getPrototypeOf = reNative.test(getPrototypeOf = Object.getPrototypeOf) && getPrototypeOf,
       hasOwnProperty = objectRef.hasOwnProperty,
       push = arrayRef.push,
-      propertyIsEnumerable = objectRef.propertyIsEnumerable,
       toString = objectRef.toString;
 
   /* Native method shortcuts for methods with the same name as other `lodash` methods */
@@ -153,7 +152,7 @@
   var hasObjectSpliceBug = (hasObjectSpliceBug = { '0': 1, 'length': 1 },
     arrayRef.splice.call(hasObjectSpliceBug, 0, 1), hasObjectSpliceBug[0]);
 
-  /** Detect if an `arguments` object's indexes are non-enumerable (IE < 9) */
+  /** Detect if `arguments` object indexes are non-enumerable (Firefox < 4, IE < 9, Safari < 5.1) */
   var nonEnumArgs = true;
 
   (function() {
@@ -164,7 +163,7 @@
     for (prop in arguments) { nonEnumArgs = !prop; }
 
     hasDontEnumBug = !/valueOf/.test(props);
-    hasEnumPrototype = propertyIsEnumerable.call(ctor, 'prototype');
+    hasEnumPrototype = ctor.propertyIsEnumerable('prototype');
     iteratesOwnLast = props[0] != 'x';
   }(1));
 
@@ -392,8 +391,7 @@
 
     // avoid iterating over `prototype` properties in older Firefox, Opera, and Safari
     '  <% if (hasEnumPrototype) { %>\n' +
-    "  var skipProto = typeof iterable == 'function' && \n" +
-    "    propertyIsEnumerable.call(iterable, 'prototype');\n" +
+    "  var skipProto = typeof iterable == 'function';\n" +
     '  <% } %>' +
 
     // iterate own properties using `Object.keys` if it's fast
@@ -710,13 +708,13 @@
     // create the function factory
     var factory = Function(
         'createCallback, hasOwnProperty, isArguments, isArray, isString, ' +
-        'objectTypes, nativeKeys, propertyIsEnumerable',
+        'objectTypes, nativeKeys',
       'return function(' + args + ') {\n' + iteratorTemplate(data) + '\n}'
     );
     // return the compiled function
     return factory(
       createCallback, hasOwnProperty, isArguments, isArray, isString,
-      objectTypes, nativeKeys, propertyIsEnumerable
+      objectTypes, nativeKeys
     );
   }
 
@@ -728,6 +726,7 @@
    * iteration early by explicitly returning `false`.
    *
    * @private
+   * @type Function
    * @param {Array|Object|String} collection The collection to iterate over.
    * @param {Function} [callback=identity] The function called per iteration.
    * @param {Mixed} [thisArg] The `this` binding of `callback`.
@@ -855,6 +854,7 @@
    *
    * @static
    * @memberOf _
+   * @type Function
    * @category Objects
    * @param {Object} object The object to iterate over.
    * @param {Function} [callback=identity] The function called per iteration.
@@ -887,6 +887,7 @@
    *
    * @static
    * @memberOf _
+   * @type Function
    * @category Objects
    * @param {Object} object The object to iterate over.
    * @param {Function} [callback=identity] The function called per iteration.
@@ -937,10 +938,14 @@
    * // => ['one', 'two', 'three'] (order is not guaranteed)
    */
   var keys = !nativeKeys ? shimKeys : function(object) {
-    // avoid iterating over the `prototype` property
-    return hasEnumPrototype && typeof object == 'function' && propertyIsEnumerable.call(object, 'prototype')
-      ? shimKeys(object)
-      : (isObject(object) ? nativeKeys(object) : []);
+    if (!isObject(object)) {
+      return [];
+    }
+    if ((hasEnumPrototype && typeof object == 'function') ||
+        (nonEnumArgs && object.length && isArguments(object))) {
+      return shimKeys(object);
+    }
+    return nativeKeys(object);
   };
 
   /**
@@ -1027,6 +1032,7 @@
    *
    * @static
    * @memberOf _
+   * @type Function
    * @alias extend
    * @category Objects
    * @param {Object} object The destination object.
@@ -1220,6 +1226,7 @@
    *
    * @static
    * @memberOf _
+   * @type Function
    * @category Objects
    * @param {Object} object The destination object.
    * @param {Object} [source1, source2, ...] The source objects.