fix: react 18 new hydration API

package.json

@@ -115,7 +115,9 @@
     "pretty-bytes": "5.3.0",
     "pretty-ms": "7.0.0",
     "react": "17.0.2",
+    "react-18": "npm:react@18",
     "react-dom": "17.0.2",
+    "react-dom-18": "npm:react-dom@18",
     "react-ssr-prepass": "1.0.8",
     "release": "6.3.0",
     "request-promise-core": "1.1.2",

packages/next/client/index.tsx

@@ -493,8 +493,10 @@ export function renderError(renderErrorProps: RenderErrorProps): Promise<any> {
     })
 }
 
+const ReactDOM18: any = ReactDOM as any
 let reactRoot: any = null
-let shouldHydrate: boolean = typeof ReactDOM.hydrate === 'function'
+let shouldHydrate: boolean =
+  typeof (ReactDOM.hydrate || ReactDOM18.hydrateRoot) === 'function'
 
 function renderReactElement(
   domEl: HTMLElement,
@@ -508,12 +510,14 @@ function renderReactElement(
   const reactEl = fn(shouldHydrate ? markHydrateComplete : markRenderComplete)
   if (process.env.__NEXT_REACT_ROOT) {
     if (!reactRoot) {
-      reactRoot = (ReactDOM as any).createRoot(domEl, {
-        hydrate: shouldHydrate,
-      })
+      if (shouldHydrate && typeof ReactDOM18.hydrateRoot === 'function') {
+        reactRoot = ReactDOM18.hydrateRoot(domEl, reactEl)
+      } else {
+        reactRoot = ReactDOM18.createRoot(domEl, { hydrate: shouldHydrate })
+        reactRoot.render(reactEl)
+      }
+      shouldHydrate = false
     }
-    reactRoot.render(reactEl)
-    shouldHydrate = false
   } else {
     // The check for `.hydrate` is there to support React alternatives like preact
     if (shouldHydrate) {

test/integration/react-18/supported/next.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  experimental: {
+    reactRoot: true,
+  },
+}

test/integration/react-18/supported/pages/index.js

@@ -1,3 +1,7 @@
 export default function Index() {
+  if (typeof window !== 'undefined') {
+    window.didHydrate = true
+  }
+  return 'details'
   return <p>Hello</p>
 }

test/integration/react-18/test/index.test.js

@@ -1,7 +1,16 @@
 /* eslint-env jest */
 
-import { findPort, killApp, launchApp, runNextCommand } from 'next-test-utils'
 import { join } from 'path'
+import fs from 'fs-extra'
+import webdriver from 'next-webdriver'
+import {
+  findPort,
+  killApp,
+  launchApp,
+  runNextCommand,
+  nextBuild,
+  nextStart,
+} from 'next-test-utils'
 
 jest.setTimeout(1000 * 60 * 5)
 
@@ -67,4 +76,30 @@ describe('React 18 Support', () => {
       expect(output).toMatch(UNSUPPORTED_PRERELEASE)
     })
   })
+
+  describe('hydration', () => {
+    const appDir = join(__dirname, '../prerelease')
+    let app
+    let appPort
+    beforeAll(async () => {
+      jest.mock('react', () => {
+        return jest.requireActual('react-18')
+      })
+      jest.mock('react-dom', () => {
+        return jest.requireActual('react-dom-18')
+      })
+      await fs.remove(join(appDir, '.next'))
+      const { stderr } = await nextBuild(appDir, [dirPrerelease], {
+        stderr: true,
+      })
+      console.error(stderr)
+      appPort = await findPort()
+      app = await nextStart(appDir, appPort, { stderr: true })
+    })
+    afterAll(async () => await killApp(app))
+    it('hydrates correctly for normal page', async () => {
+      const browser = await webdriver(appPort, '/')
+      expect(await browser.eval('window.didHydrate')).toBe(true)
+    })
+  })
 })

yarn.lock

@@ -15632,6 +15632,23 @@ rc@^1.0.1, rc@^1.1.6, rc@^1.2.7, rc@^1.2.8:
     minimist "^1.2.0"
     strip-json-comments "~2.0.1"
 
+"react-18@npm:react@18":
+  version "18.0.0-alpha-e6be2d531"
+  resolved "https://registry.yarnpkg.com/react/-/react-18.0.0-alpha-e6be2d531.tgz#c5cf6d5706f7b6411d36848b483a7937c94fc5c9"
+  integrity sha512-roZmm4MYfuGN65PiagPvhumBb3Da1FAgyj6Ti2sHwQDIxhi40PMq5V90gBSKXl7qXbaXHrtpuAtG5R+XkqpDYA==
+  dependencies:
+    loose-envify "^1.1.0"
+    object-assign "^4.1.1"
+
+"react-dom-18@npm:react-dom@18":
+  version "18.0.0-alpha-e6be2d531"
+  resolved "https://registry.yarnpkg.com/react-dom/-/react-dom-18.0.0-alpha-e6be2d531.tgz#89b1aef488a56ceac7cc0169ae02d7fbb58cbbb6"
+  integrity sha512-mMGiX/kyhxaUTRDt+Q5oIbpU6cPvO8Sp/kHz3cdNFviwVTHHF2YrnnD70BD2F1R0b7wAdfVVit9EfE+Rqt0sJA==
+  dependencies:
+    loose-envify "^1.1.0"
+    object-assign "^4.1.1"
+    scheduler "0.21.0-alpha-e6be2d531"
+
 react-dom@17.0.2:
   version "17.0.2"
   resolved "https://registry.yarnpkg.com/react-dom/-/react-dom-17.0.2.tgz#ecffb6845e3ad8dbfcdc498f0d0a939736502c23"
@@ -16649,6 +16666,14 @@ saxes@^5.0.1:
   dependencies:
     xmlchars "^2.2.0"
 
+scheduler@0.21.0-alpha-e6be2d531:
+  version "0.21.0-alpha-e6be2d531"
+  resolved "https://registry.yarnpkg.com/scheduler/-/scheduler-0.21.0-alpha-e6be2d531.tgz#fd895f7426e15166f1b16ed1d54de48243c78002"
+  integrity sha512-1GSnBp3em+oMz93ncjqR/7qeGArhgKaOWluZUrQW2JgHEGYISXAhGTVQhUYAiKc3F9jiq94CE1WrO0vaVzgReQ==
+  dependencies:
+    loose-envify "^1.1.0"
+    object-assign "^4.1.1"
+
 scheduler@^0.20.2:
   version "0.20.2"
   resolved "https://registry.yarnpkg.com/scheduler/-/scheduler-0.20.2.tgz#4baee39436e34aa93b4874bddcbf0fe8b8b50e91"