Deprecate ReactDOM.render and ReactDOM.hydrate

fixtures/dom/src/__tests__/wrong-act-test.js

@@ -101,9 +101,15 @@ it('warns when using the wrong act version - test + dom: render', () => {
     TestRenderer.act(() => {
       ReactDOM.render(<App />, document.createElement('div'));
     });
-  }).toWarnDev(["It looks like you're using the wrong act()"], {
-    withoutStack: true,
-  });
+  }).toWarnDev(
+    [
+      'ReactDOM.render is no longer supported in React 18.',
+      "It looks like you're using the wrong act()",
+    ],
+    {
+      withoutStack: true,
+    }
+  );
 });
 
 it('warns when using the wrong act version - test + dom: updates', () => {

packages/react-devtools-shared/src/__tests__/inspectedElement-test.js

@@ -390,9 +390,8 @@ describe('InspectedElement', () => {
     });
 
     const container = document.createElement('div');
-    await utils.actAsync(() =>
-      ReactDOM.render(<Target a={1} b="abc" />, container),
-    );
+    const root = ReactDOM.createRoot(container);
+    await utils.actAsync(() => root.render(<Target a={1} b="abc" />));
 
     expect(targetRenderCount).toBe(1);
     expect(console.error).toHaveBeenCalledTimes(1);

packages/react-dom/src/__tests__/ReactDOMFiber-test.js

@@ -1154,9 +1154,15 @@ describe('ReactDOMFiber', () => {
     expect(ops).toEqual(['A']);
 
     if (__DEV__) {
-      // TODO: this warning shouldn't be firing in the first place if user didn't call it.
       const errorCalls = console.error.calls.count();
-      for (let i = 0; i < errorCalls; i++) {
+      expect(console.error.calls.argsFor(0)[0]).toMatch(
+        'ReactDOM.render is no longer supported in React 18',
+      );
+      expect(console.error.calls.argsFor(1)[0]).toMatch(
+        'ReactDOM.render is no longer supported in React 18',
+      );
+      // TODO: this warning shouldn't be firing in the first place if user didn't call it.
+      for (let i = 2; i < errorCalls; i++) {
         expect(console.error.calls.argsFor(i)[0]).toMatch(
           'unstable_flushDiscreteUpdates: Cannot flush updates when React is already rendering.',
         );

packages/react-dom/src/__tests__/ReactErrorBoundaries-test.internal.js

@@ -787,16 +787,22 @@ describe('ReactErrorBoundaries', () => {
 
   it('logs a single error when using error boundary', () => {
     const container = document.createElement('div');
-    expect(() =>
-      ReactDOM.render(
-        <ErrorBoundary>
-          <BrokenRender />
-        </ErrorBoundary>,
-        container,
-      ),
-    ).toErrorDev('The above error occurred in the <BrokenRender> component:', {
-      logAllErrors: true,
-    });
+    spyOnDev(console, 'error');
+    ReactDOM.render(
+      <ErrorBoundary>
+        <BrokenRender />
+      </ErrorBoundary>,
+      container,
+    );
+    if (__DEV__) {
+      expect(console.error).toHaveBeenCalledTimes(2);
+      expect(console.error.calls.argsFor(0)[0]).toContain(
+        'ReactDOM.render is no longer supported',
+      );
+      expect(console.error.calls.argsFor(1)[0]).toContain(
+        'The above error occurred in the <BrokenRender> component:',
+      );
+    }
 
     expect(container.firstChild.textContent).toBe('Caught an error: Hello.');
     expect(Scheduler).toHaveYielded([

packages/react-dom/src/__tests__/ReactErrorLoggingRecovery-test.js

@@ -43,6 +43,13 @@ describe('ReactErrorLoggingRecovery', () => {
 
   beforeEach(() => {
     console.error = error => {
+      if (
+        typeof error === 'string' &&
+        error.includes('ReactDOM.render is no longer supported in React 18')
+      ) {
+        // Ignore legacy root deprecation warning
+        return;
+      }
       throw new Error('Buggy console.error');
     };
   });

packages/react-dom/src/__tests__/ReactLegacyErrorBoundaries-test.internal.js

@@ -668,16 +668,22 @@ describe('ReactLegacyErrorBoundaries', () => {
 
   it('logs a single error using both error boundaries', () => {
     const container = document.createElement('div');
-    expect(() =>
-      ReactDOM.render(
-        <BothErrorBoundaries>
-          <BrokenRender />
-        </BothErrorBoundaries>,
-        container,
-      ),
-    ).toErrorDev('The above error occurred in the <BrokenRender> component', {
-      logAllErrors: true,
-    });
+    spyOnDev(console, 'error');
+    ReactDOM.render(
+      <BothErrorBoundaries>
+        <BrokenRender />
+      </BothErrorBoundaries>,
+      container,
+    );
+    if (__DEV__) {
+      expect(console.error).toHaveBeenCalledTimes(2);
+      expect(console.error.calls.argsFor(0)[0]).toContain(
+        'ReactDOM.render is no longer supported',
+      );
+      expect(console.error.calls.argsFor(1)[0]).toContain(
+        'The above error occurred in the <BrokenRender> component:',
+      );
+    }
 
     expect(container.firstChild.textContent).toBe('Caught an error: Hello.');
     expect(log).toEqual([

packages/react-dom/src/__tests__/ReactLegacyRootWarnings-test.js

@@ -0,0 +1,38 @@
+let ReactDOM = require('react-dom');
+
+describe('ReactDOMRoot', () => {
+  let container;
+
+  beforeEach(() => {
+    jest.resetModules();
+    container = document.createElement('div');
+    ReactDOM = require('react-dom');
+  });
+
+  test('deprecation warning for ReactDOM.render', () => {
+    spyOnDev(console, 'error');
+
+    ReactDOM.render('Hi', container);
+    expect(container.textContent).toEqual('Hi');
+    if (__DEV__) {
+      expect(console.error).toHaveBeenCalledTimes(1);
+      expect(console.error.calls.argsFor(0)[0]).toContain(
+        'ReactDOM.render is no longer supported',
+      );
+    }
+  });
+
+  test('deprecation warning for ReactDOM.hydrate', () => {
+    spyOnDev(console, 'error');
+
+    container.innerHTML = 'Hi';
+    ReactDOM.hydrate('Hi', container);
+    expect(container.textContent).toEqual('Hi');
+    if (__DEV__) {
+      expect(console.error).toHaveBeenCalledTimes(1);
+      expect(console.error.calls.argsFor(0)[0]).toContain(
+        'ReactDOM.hydrate is no longer supported',
+      );
+    }
+  });
+});

packages/react-dom/src/__tests__/utils/ReactDOMServerIntegrationTestUtils.js

@@ -10,6 +10,7 @@
 'use strict';
 
 const stream = require('stream');
+const shouldIgnoreConsoleError = require('../../../../../scripts/jest/shouldIgnoreConsoleError');
 
 module.exports = function(initModules) {
   let ReactDOM;
@@ -74,23 +75,29 @@ module.exports = function(initModules) {
     }
 
     const result = await fn();
-    if (
-      console.error.calls &&
-      console.error.calls.count() !== count &&
-      console.error.calls.count() !== 0
-    ) {
-      console.log(
-        `We expected ${count} warning(s), but saw ${console.error.calls.count()} warning(s).`,
-      );
-      if (console.error.calls.count() > 0) {
-        console.log(`We saw these warnings:`);
-        for (let i = 0; i < console.error.calls.count(); i++) {
-          console.log(...console.error.calls.argsFor(i));
+    if (console.error.calls && console.error.calls.count() !== 0) {
+      const filteredWarnings = [];
+      for (let i = 0; i < console.error.calls.count(); i++) {
+        const args = console.error.calls.argsFor(i);
+        const [format, ...rest] = args;
+        if (!shouldIgnoreConsoleError(format, rest)) {
+          filteredWarnings.push(args);
+        }
+      }
+      if (filteredWarnings.length !== count) {
+        console.log(
+          `We expected ${count} warning(s), but saw ${filteredWarnings.length} warning(s).`,
+        );
+        if (filteredWarnings.count > 0) {
+          console.log(`We saw these warnings:`);
+          for (let i = 0; i < filteredWarnings.length; i++) {
+            console.log(...filteredWarnings[i]);
+          }
+        }
+        if (__DEV__) {
+          expect(console.error).toHaveBeenCalledTimes(count);
         }
       }
-    }
-    if (__DEV__) {
-      expect(console.error).toHaveBeenCalledTimes(count);
     }
     return result;
   }

packages/react-dom/src/client/ReactDOMLegacy.js

@@ -219,6 +219,15 @@ export function hydrate(
   container: Container,
   callback: ?Function,
 ) {
+  if (__DEV__) {
+    console.error(
+      'ReactDOM.hydrate is no longer supported in React 18. Use createRoot ' +
+        'instead. Until you switch to the new API, your app will behave as ' +
+        "if it's running React 17. Learn " +
+        'more: https://reactjs.org/link/switch-to-createroot',
+    );
+  }
+
   invariant(
     isValidContainer(container),
     'Target container is not a DOM element.',
@@ -250,6 +259,15 @@ export function render(
   container: Container,
   callback: ?Function,
 ) {
+  if (__DEV__) {
+    console.error(
+      'ReactDOM.render is no longer supported in React 18. Use createRoot ' +
+        'instead. Until you switch to the new API, your app will behave as ' +
+        "if it's running React 17. Learn " +
+        'more: https://reactjs.org/link/switch-to-createroot',
+    );
+  }
+
   invariant(
     isValidContainer(container),
     'Target container is not a DOM element.',

scripts/jest/shouldIgnoreConsoleError.js

@@ -13,6 +13,16 @@ module.exports = function shouldIgnoreConsoleError(format, args) {
         // Ignore it too.
         return true;
       }
+      if (
+        format.indexOf('ReactDOM.render is no longer supported in React 18') !==
+          -1 ||
+        format.indexOf(
+          'ReactDOM.hydrate is no longer supported in React 18'
+        ) !== -1
+      ) {
+        // We haven't finished migrating our tests to use createRoot.
+        return true;
+      }
     }
   } else {
     if (