Change ReactChildrenMutationWarningHook to Object.freeze children

src/isomorphic/classic/element/ReactElement.js

@@ -135,7 +135,6 @@ var ReactElement = function(type, key, ref, self, source, owner, props) {
     // This can be replaced with a WeakMap once they are implemented in
     // commonly used development environments.
     element._store = {};
-    var shadowChildren = Array.isArray(props.children) ? props.children.slice(0) : props.children;
 
     // To make comparing ReactElements easier for testing purposes, we make
     // the validation flag non-enumerable (where possible, which should
@@ -155,12 +154,6 @@ var ReactElement = function(type, key, ref, self, source, owner, props) {
         writable: false,
         value: self,
       });
-      Object.defineProperty(element, '_shadowChildren', {
-        configurable: false,
-        enumerable: false,
-        writable: false,
-        value: shadowChildren,
-      });
       // Two elements created in two different places should be considered
       // equal for testing purposes and therefore we hide it from enumeration.
       Object.defineProperty(element, '_source', {
@@ -172,7 +165,6 @@ var ReactElement = function(type, key, ref, self, source, owner, props) {
     } else {
       element._store.validated = false;
       element._self = self;
-      element._shadowChildren = shadowChildren;
       element._source = source;
     }
     if (Object.freeze) {
@@ -238,6 +230,11 @@ ReactElement.createElement = function(type, config, children) {
     for (var i = 0; i < childrenLength; i++) {
       childArray[i] = arguments[i + 2];
     }
+    if (__DEV__) {
+      if (Object.freeze) {
+        Object.freeze(childArray);
+      }
+    }
     props.children = childArray;
   }
 

src/renderers/dom/server/__tests__/ReactServerRendering-test.js

@@ -539,37 +539,20 @@ describe('ReactServerRendering', () => {
     expect(markup).toBe('<div></div>');
   });
 
-  it('warns when children are mutated before render', () => {
-    function normalizeCodeLocInfo(str) {
-      return str.replace(/\(at .+?:\d+\)/g, '(at **)');
-    }
-
+  it('should warn when children are mutated during render', () => {
     spyOn(console, 'error');
-    var children = [<span key={0} />, <span key={1} />, <span key={2} />];
-    var element = <div>{children}</div>;
-    children[1] = <p key={1} />; // Mutation is illegal
-    ReactServerRendering.renderToString(element);
-    expect(console.error.calls.count()).toBe(1);
-    expect(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
-      'Warning: Component\'s children should not be mutated.\n    in div (at **)'
-    );
-  });
-
-  it('should warn when children are mutated', () => {
-    function normalizeCodeLocInfo(str) {
-      return str.replace(/\(at .+?:\d+\)/g, '(at **)');
-    }
-
-    spyOn(console, 'error');
-    var children = [<span key={0} />, <span key={1} />, <span key={2} />];
     function Wrapper(props) {
       props.children[1] = <p key={1} />; // Mutation is illegal
       return <div>{props.children}</div>;
     }
-    ReactServerRendering.renderToString(<Wrapper>{children}</Wrapper>);
-    expect(console.error.calls.count()).toBe(1);
-    expect(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
-      'Warning: Component\'s children should not be mutated.\n    in Wrapper (at **)'
-    );
+    expect(() => {
+      ReactServerRendering.renderToStaticMarkup(
+        <Wrapper>
+          <span key={0}/>
+          <span key={1}/>
+          <span key={2}/>
+        </Wrapper>
+      );
+    }).toThrowError(/Cannot assign to read only property.*/);
   });
 });

src/renderers/shared/ReactDebugTool.js

@@ -15,7 +15,6 @@
 var ReactInvalidSetStateWarningHook = require('ReactInvalidSetStateWarningHook');
 var ReactHostOperationHistoryHook = require('ReactHostOperationHistoryHook');
 var ReactComponentTreeHook = require('ReactComponentTreeHook');
-var ReactChildrenMutationWarningHook = require('ReactChildrenMutationWarningHook');
 var ExecutionEnvironment = require('ExecutionEnvironment');
 
 var performanceNow = require('performanceNow');
@@ -417,7 +416,6 @@ var ReactDebugTool = {
 
 ReactDebugTool.addHook(ReactInvalidSetStateWarningHook);
 ReactDebugTool.addHook(ReactComponentTreeHook);
-ReactDebugTool.addHook(ReactChildrenMutationWarningHook);
 var url = (ExecutionEnvironment.canUseDOM && window.location.href) || '';
 if ((/[?&]react_perf\b/).test(url)) {
   ReactDebugTool.beginProfiling();

src/renderers/shared/stack/reconciler/__tests__/ReactComponent-test.js

@@ -15,10 +15,6 @@ var React;
 var ReactDOM;
 var ReactTestUtils;
 
-function normalizeCodeLocInfo(str) {
-  return str.replace(/\(at .+?:\d+\)/g, '(at **)');
-}
-
 describe('ReactComponent', () => {
   beforeEach(() => {
     React = require('React');
@@ -49,30 +45,46 @@ describe('ReactComponent', () => {
     }).toThrow();
   });
 
-  it('should warn when children are mutated before render', () => {
-    spyOn(console, 'error');
-    var children = [<span key={0} />, <span key={1} />, <span key={2} />];
-    var element = <div>{children}</div>;
-    children[1] = <p key={1} />; // Mutation is illegal
-    ReactTestUtils.renderIntoDocument(element);
-    expect(console.error.calls.count()).toBe(1);
-    expect(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
-      'Warning: Component\'s children should not be mutated.\n    in div (at **)'
-    );
-  });
-
-  it('should warn when children are mutated', () => {
+  it('should warn when children are mutated during render', () => {
     spyOn(console, 'error');
-    var children = [<span key={0} />, <span key={1} />, <span key={2} />];
     function Wrapper(props) {
       props.children[1] = <p key={1} />; // Mutation is illegal
       return <div>{props.children}</div>;
     }
-    ReactTestUtils.renderIntoDocument(<Wrapper>{children}</Wrapper>);
-    expect(console.error.calls.count()).toBe(1);
-    expect(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
-      'Warning: Component\'s children should not be mutated.\n    in Wrapper (at **)'
-    );
+    expect(() => {
+      ReactTestUtils.renderIntoDocument(
+        <Wrapper>
+          <span key={0}/>
+          <span key={1}/>
+          <span key={2}/>
+        </Wrapper>
+      );
+    }).toThrowError(/Cannot assign to read only property.*/);
+  });
+
+  it('should warn when children are mutated during update', () => {
+    spyOn(console, 'error');
+
+    class Wrapper extends React.Component {
+      componentDidMount() {
+        this.props.children[1] = <p key={1} />; // Mutation is illegal
+        this.forceUpdate();
+      }
+
+      render() {
+        return <div>{this.props.children}</div>;
+      }
+    }
+
+    expect(() => {
+      ReactTestUtils.renderIntoDocument(
+        <Wrapper>
+          <span key={0}/>
+          <span key={1}/>
+          <span key={2}/>
+        </Wrapper>
+      );
+    }).toThrowError(/Cannot assign to read only property.*/);
   });
 
   it('should support refs on owned components', () => {