Warn if props obj passed into createElement / cloneElement inherits f…

…rom anything other than Object

src/isomorphic/classic/element/ReactElement.js

@@ -127,6 +127,13 @@ ReactElement.createElement = function(type, config, children) {
 
   if (config != null) {
     if (__DEV__) {
+      warning(
+        /* eslint-disable no-proto */
+        config.__proto__ == null || config.__proto__ === Object.prototype,
+        /* eslint-enable no-proto */
+        'React.createElement(...): Expected props argument to be a plain object. ' +
+        'Properties defined in its prototype chain will be ignored.'
+      );
       ref = !config.hasOwnProperty('ref') ||
         Object.getOwnPropertyDescriptor(config, 'ref').get ? null : config.ref;
       key = !config.hasOwnProperty('key') ||
@@ -269,6 +276,15 @@ ReactElement.cloneElement = function(element, config, children) {
   var owner = element._owner;
 
   if (config != null) {
+    if (__DEV__) {
+      warning(
+        /* eslint-disable no-proto */
+        config.__proto__ == null || config.__proto__ === Object.prototype,
+        /* eslint-enable no-proto */
+        'React.cloneElement(...): Expected props argument to be a plain object. ' +
+        'Properties defined in its prototype chain will be ignored.'
+      );
+    }
     if (config.ref !== undefined) {
       // Silently steal the ref from the parent.
       ref = config.ref;

src/isomorphic/classic/element/__tests__/ReactElement-test.js

@@ -139,6 +139,18 @@ describe('ReactElement', function() {
     expect(element.props.foo).toBe(1);
   });
 
+  it('warns if the config object inherits from any type other than Object', function() {
+    spyOn(console, 'error');
+    React.createElement('div', {foo: 1});
+    expect(console.error).not.toHaveBeenCalled();
+    React.createElement('div', Object.create({foo: 1}));
+    expect(console.error.argsForCall.length).toBe(1);
+    expect(console.error.argsForCall[0][0]).toContain(
+      'React.createElement(...): Expected props argument to be a plain object. ' +
+      'Properties defined in its prototype chain will be ignored.'
+    );
+  });
+
   it('extracts key and ref from the config', function() {
     var element = React.createFactory(ComponentClass)({
       key: '12',

src/isomorphic/classic/element/__tests__/ReactElementClone-test.js

@@ -66,6 +66,18 @@ describe('ReactElementClone', function() {
     expect(ReactDOM.findDOMNode(component).childNodes[0].className).toBe('xyz');
   });
 
+  it('should warn if the config object inherits from any type other than Object', function() {
+    spyOn(console, 'error');
+    React.cloneElement('div', {foo: 1});
+    expect(console.error).not.toHaveBeenCalled();
+    React.cloneElement('div', Object.create({foo: 1}));
+    expect(console.error.argsForCall.length).toBe(1);
+    expect(console.error.argsForCall[0][0]).toContain(
+      'React.cloneElement(...): Expected props argument to be a plain object. ' +
+      'Properties defined in its prototype chain will be ignored.'
+    );
+  });
+
   it('should keep the original ref if it is not overridden', function() {
     var Grandparent = React.createClass({
       render: function() {