Fix cloneWithProps() to allow overriding props

This is a clear bug.

src/utils/__tests__/cloneWithProps-test.js

@@ -55,7 +55,7 @@ describe('cloneWithProps', function() {
     });
     var component = ReactTestUtils.renderIntoDocument(<Grandparent />);
     expect(component.getDOMNode().childNodes[0].className)
-      .toBe('child xyz');
+      .toBe('xyz child');
   });
 
   it('should clone a composite component with new props', function() {
@@ -82,7 +82,7 @@ describe('cloneWithProps', function() {
     });
     var component = ReactTestUtils.renderIntoDocument(<Grandparent />);
     expect(component.getDOMNode().childNodes[0].className)
-      .toBe('child xyz');
+      .toBe('xyz child');
   });
 
   it('should warn when cloning with refs', function() {
@@ -178,4 +178,17 @@ describe('cloneWithProps', function() {
 
     ReactTestUtils.renderIntoDocument(<Grandparent />);
   });
+
+  it('should overwrite props', function() {
+    var Component = React.createClass({
+      render: function() {
+        expect(this.props.myprop).toBe('xyz');
+        return <div />;
+      }
+    });
+
+    ReactTestUtils.renderIntoDocument(
+      cloneWithProps(<Component myprop="abc" />, {myprop: 'xyz'})
+    );
+  });
 });

src/utils/cloneWithProps.js

@@ -21,13 +21,9 @@
 
 var ReactPropTransferer = require('ReactPropTransferer');
 
-var keyMirror = require('keyMirror');
+var keyOf = require('keyOf');
 
-var SpecialPropsToTransfer = keyMirror({
-  key: null,
-  children: null,
-  ref: null
-});
+var CHILDREN_PROP = keyOf({children: null});
 
 /**
  * Sometimes you want to change the props of a child passed to you. Usually
@@ -49,28 +45,14 @@ function cloneWithProps(child, props) {
     }
   }
 
-  var newProps = ReactPropTransferer.mergeProps(child.props, props);
+  var newProps = ReactPropTransferer.mergeProps(props, child.props);
 
-  // ReactPropTransferer does not transfer the `key` prop so do it manually. Do
-  // not transfer it from the original component.
-  if (props.hasOwnProperty(SpecialPropsToTransfer.key)) {
-    newProps.key = props.key;
-  }
-
-  // ReactPropTransferer does not transfer the `children` prop. Transfer it
-  // from `props` if it exists, otherwise use `child.props.children` if it is
-  // provided.
-  if (props.hasOwnProperty(SpecialPropsToTransfer.children)) {
-    newProps.children = props.children;
-  } else if (child.props.hasOwnProperty(SpecialPropsToTransfer.children)) {
+  // Use `child.props.children` if it is provided.
+  if (!newProps.hasOwnProperty(CHILDREN_PROP) &&
+      child.props.hasOwnProperty(CHILDREN_PROP)) {
     newProps.children = child.props.children;
   }
 
-  // ReactPropTransferer does not transfer `ref` so do it manually.
-  if (props.hasOwnProperty(SpecialPropsToTransfer.ref)) {
-    newProps.ref = props.ref;
-  }
-
   return child.constructor.ConvenienceConstructor(newProps);
 }