Added DEV warning if getSnapshotBeforeUpdate is defined as a static method (#12475)

Author: bvaughn

packages/react-reconciler/src/ReactFiberClassComponent.js

@@ -398,6 +398,14 @@ export default function(
           'and will be ignored. Instead, declare it as a static method.',
         name,
       );
+      const noStaticGetSnapshotBeforeUpdate =
+        typeof type.getSnapshotBeforeUpdate !== 'function';
+      warning(
+        noStaticGetSnapshotBeforeUpdate,
+        '%s: getSnapshotBeforeUpdate() is defined as a static method ' +
+          'and will be ignored. Instead, declare it as an instance method.',
+        name,
+      );
       const state = instance.state;
       if (state && (typeof state !== 'object' || isArray(state))) {
         warning(false, '%s.state: must be set to an object or null', name);

packages/react/src/__tests__/ReactCoffeeScriptClass-test.coffee

@@ -140,6 +140,17 @@ describe 'ReactCoffeeScriptClass', ->
     ).toWarnDev 'Foo: getDerivedStateFromCatch() is defined as an instance method and will be ignored. Instead, declare it as a static method.',
     undefined
 
+  it 'warns if getSnapshotBeforeUpdate is static', ->
+    class Foo extends React.Component
+      render: ->
+        div()
+    Foo.getSnapshotBeforeUpdate = () ->
+      {}
+    expect(->
+      ReactDOM.render(React.createElement(Foo, foo: 'foo'), container)
+    ).toWarnDev 'Foo: getSnapshotBeforeUpdate() is defined as a static method and will be ignored. Instead, declare it as an instance method.',
+    undefined
+
   it 'warns if state not initialized before static getDerivedStateFromProps', ->
     class Foo extends React.Component
       render: ->

packages/react/src/__tests__/ReactES6Class-test.js

@@ -158,6 +158,19 @@ describe('ReactES6Class', () => {
     );
   });
 
+  it('warns if getSnapshotBeforeUpdate is static', () => {
+    class Foo extends React.Component {
+      static getSnapshotBeforeUpdate() {}
+      render() {
+        return <div />;
+      }
+    }
+    expect(() => ReactDOM.render(<Foo foo="foo" />, container)).toWarnDev(
+      'Foo: getSnapshotBeforeUpdate() is defined as a static method ' +
+        'and will be ignored. Instead, declare it as an instance method.',
+    );
+  });
+
   it('warns if state not initialized before static getDerivedStateFromProps', () => {
     class Foo extends React.Component {
       static getDerivedStateFromProps(nextProps, prevState) {

packages/react/src/__tests__/ReactTypeScriptClass-test.ts

@@ -412,6 +412,22 @@ describe('ReactTypeScriptClass', function() {
     );
   });
 
+  it('warns if getSnapshotBeforeUpdate is static', function() {
+    class Foo extends React.Component {
+      static getSnapshotBeforeUpdate() {
+      }
+      render() {
+        return React.createElement('div', {});
+      }
+    }
+    expect(function() {
+      ReactDOM.render(React.createElement(Foo, {foo: 'foo'}), container);
+    }).toWarnDev(
+      'Foo: getSnapshotBeforeUpdate() is defined as a static method ' +
+        'and will be ignored. Instead, declare it as an instance method.'
+    );
+  });
+
   it('warns if state not initialized before static getDerivedStateFromProps', function() {
     class Foo extends React.Component {
       static getDerivedStateFromProps(nextProps, prevState) {

packages/react/src/__tests__/createReactClassIntegration-test.js

@@ -467,6 +467,25 @@ describe('create-react-class-integration', () => {
     );
   });
 
+  it('warns if getSnapshotBeforeUpdate is static', () => {
+    const Foo = createReactClass({
+      statics: {
+        getSnapshotBeforeUpdate: function() {
+          return null;
+        },
+      },
+      render() {
+        return <div />;
+      },
+    });
+    expect(() =>
+      ReactDOM.render(<Foo foo="foo" />, document.createElement('div')),
+    ).toWarnDev(
+      'Component: getSnapshotBeforeUpdate() is defined as a static method ' +
+        'and will be ignored. Instead, declare it as an instance method.',
+    );
+  });
+
   it('should warn if state is not properly initialized before getDerivedStateFromProps', () => {
     const Component = createReactClass({
       statics: {