[Fix] SetProps - Children objects should be new instances

src/ReactWrapper.jsx

@@ -14,6 +14,8 @@ import {
   nodeEqual,
   nodeMatches,
   getAdapter,
+  shouldCloneChildren,
+  cloneChildren,
 } from './Utils';
 import {
   debugNodes,
@@ -303,6 +305,12 @@ class ReactWrapper {
     if (typeof callback !== 'function') {
       throw new TypeError('ReactWrapper::setProps() expects a function as its second argument');
     }
+    const instance = this.getNodeInternal();
+    const adapter = getAdapter(this.options);
+    if (shouldCloneChildren(instance, props, adapter)) {
+      props = props || {}; // eslint-disable-line no-param-reassign
+      props.children = cloneChildren(instance); // eslint-disable-line no-param-reassign
+    }
     this.component.setChildProps(props, () => {
       this.update();
       callback();

src/Utils.js

@@ -1,4 +1,5 @@
 /* eslint no-use-before-define:0 */
+import React from 'react';
 import isEqual from 'lodash/isEqual';
 import is from 'object-is';
 import uuidv4 from 'uuid/v4';
@@ -185,6 +186,10 @@ function childrenOfNode(node) {
   return childrenToArray(children);
 }
 
+function propsHaveChildren(props) {
+  return !!(props || {}).children;
+}
+
 function isTextualNode(node) {
   return typeof node === 'string' || typeof node === 'number';
 }
@@ -193,6 +198,10 @@ export function isReactElementAlike(arg, adapter) {
   return adapter.isValidElement(arg) || isTextualNode(arg) || Array.isArray(arg);
 }
 
+function isReactObjectAlike(arg, adapter) {
+  return adapter.isValidElement(arg) || Array.isArray(arg);
+}
+
 // TODO(lmr): can we get rid of this outside of the adapter?
 export function withSetStateAllowed(fn) {
   // NOTE(lmr):
@@ -368,3 +377,12 @@ export function displayNameOfNode(node) {
 
   return type.displayName || (typeof type === 'function' ? functionName(type) : type.name || type);
 }
+
+export function shouldCloneChildren(node, newProps, adapter) {
+  // if our new props don't have children and we have an array we should clone the children
+  return !propsHaveChildren(newProps) && isReactObjectAlike(propsOfNode(node).children, adapter);
+}
+
+export function cloneChildren(node) {
+  return React.Children.map(node.props.children, (child => React.cloneElement(child)));
+}

test/ReactWrapper-spec.jsx

@@ -999,6 +999,52 @@ describeWithDOM('mount', () => {
       expect(wrapper.props().d).to.equal('e');
     });
 
+    describe('pure components with children', () => {
+      let PureComponent;
+      beforeEach(() => {
+        class Foo extends React.Component { // pure component was introduced only in react 15
+          shouldComponentUpdate(nextProps) {
+            return this.props.children !== nextProps.children;
+          }
+          render() {
+            this.renderedCount = (this.renderedCount || 0) + 1;
+            return (
+              <div>{this.props.children}</div>
+            );
+          }
+        }
+        PureComponent = Foo;
+      });
+
+      it('should not render for nothing when children are null', () => {
+        const wrapper = mount(<PureComponent />);
+        expect(wrapper.instance().renderedCount).to.equal(1);
+        wrapper.setProps({});
+        expect(wrapper.instance().renderedCount).to.equal(1);
+      });
+
+      it('should not render for nothing when children are string', () => {
+        const wrapper = mount(<PureComponent>String children</PureComponent>);
+        expect(wrapper.instance().renderedCount).to.equal(1);
+        wrapper.setProps({});
+        expect(wrapper.instance().renderedCount).to.equal(1);
+      });
+
+      it('should render for nothing because react sends a new children object', () => {
+        const wrapper = mount(<PureComponent><div>Object children</div></PureComponent>);
+        expect(wrapper.instance().renderedCount).to.equal(1);
+        wrapper.setProps({});
+        expect(wrapper.instance().renderedCount).to.equal(2);
+      });
+
+      it('should render for nothing because react sends a new children array', () => {
+        const wrapper = mount(<PureComponent><div>Child 1</div><div>Child 2</div></PureComponent>);
+        expect(wrapper.instance().renderedCount).to.equal(1);
+        wrapper.setProps({});
+        expect(wrapper.instance().renderedCount).to.equal(2);
+      });
+    });
+
     itIf(!REACT16, 'should throw if an exception occurs during render', () => {
       class Trainwreck extends React.Component {
         render() {