Make _.defaults follow _.assign and only assign own properties of source.

Former-commit-id: 114dc47bbfa6db6a53a2fa03dd477fe86c3395cb

build.js

@@ -1125,6 +1125,26 @@
           '  }'
         ].join('\n'));
 
+        // replace `_.defaults`
+        source = source.replace(/^( *)var defaults *= *createIterator[\s\S]+?\);/m, [
+          '  function defaults(object) {',
+          '    if (!object) {',
+          '      return object;',
+          '    }',
+          '    for (var argsIndex = 1, argsLength = arguments.length; argsIndex < argsLength; argsIndex++) {',
+          '      var iteratee = arguments[argsIndex];',
+          '      if (iteratee) {',
+          '        for (var key in iteratee) {',
+          '          if (object[key] == null) {',
+          '            object[key] = iteratee[key];',
+          '          }',
+          '        }',
+          '      }',
+          '    }',
+          '    return object;',
+          '  }'
+        ].join('\n'));
+
         // replace `_.intersection`
         source = source.replace(/^( *)function intersection[\s\S]+?\n\1}/m, [
           '  function intersection(array) {',

lodash.js

@@ -977,7 +977,7 @@
   }
 
   /**
-   * Assigns enumerable properties of the default object(s) to the `destination`
+   * Assigns own enumerable properties of source object(s) to the `destination`
    * object for all `destination` properties that resolve to `null`/`undefined`.
    * Once a property is set, additional defaults of the same property will be
    * ignored.
@@ -995,7 +995,6 @@
    * // => { 'flavor': 'chocolate', 'sprinkles': 'rainbow' }
    */
   var defaults = createIterator(assignIteratorOptions, {
-    'useHas': false,
     'objectLoop': 'if (result[index] == null) ' + assignIteratorOptions.objectLoop
   });
 

test/test-build.js

@@ -651,6 +651,12 @@
         equal(lodash.contains([1, 2, 3], 1, 2), true, '_.contains should ignore `fromIndex`: ' + basename);
         equal(lodash.every([true, false, true]), false, '_.every: ' + basename);
 
+        function Foo() {}
+        Foo.prototype = { 'a': 1 };
+
+        deepEqual(lodash.defaults({}, new Foo), Foo.prototype, '_.defaults should assign inherited `source` properties: ' + basename);
+        deepEqual(lodash.extend({}, new Foo), Foo.prototype, '_.extend should assign inherited `source` properties: ' + basename);
+
         actual = lodash.find(array, function(value) {
           return 'value' in value;
         });

test/test.js

@@ -421,6 +421,20 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('source property checks');
+
+  _.each(['assign', 'defaults'], function(methodName) {
+    var func = _[methodName];
+
+    test('lodash.' + methodName + ' should not assign inherited `source` properties', function() {
+      function Foo() {}
+      Foo.prototype = { 'a': 1 };
+      deepEqual(func({}, new Foo), {});
+    });
+  });
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('strict mode checks');
 
   _.each(['assign', 'bindAll', 'defaults'], function(methodName) {