Fallback to functional document when no custom document with react 18

packages/next/server/render.tsx

@@ -1301,7 +1301,14 @@ export async function renderToHTML(
       }
     }
 
-    if ((isServerComponent || process.browser) && Document.getInitialProps) {
+    if (
+      // If it's server component, edge runtime or using default document with react 18,
+      // try to fallback to built-in functional document
+      (isServerComponent ||
+        process.browser ||
+        (builtinDocument && hasConcurrentFeatures)) &&
+      Document.getInitialProps
+    ) {
       if (builtinDocument) {
         Document = builtinDocument
       } else {

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

@@ -1,7 +1,13 @@
 import ReactDOM from 'react-dom'
 import Image from 'next/image'
 
+function sideEffectCall() {
+  console.log('sideEffectCall')
+}
+
 export default function Index() {
+  sideEffectCall()
+
   if (typeof window !== 'undefined') {
     window.didHydrate = true
   }

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

@@ -5,6 +5,14 @@ import cheerio from 'cheerio'
 import { renderViaHTTP } from 'next-test-utils'
 
 export default (context, env) => {
+  it('should render page on server side only once if there is no custom document', async () => {
+    await renderViaHTTP(context.appPort, '/')
+    const firstIndex = context.stdout.indexOf('sideEffectCall')
+    const lastIndex = context.stdout.lastIndexOf('sideEffectCall')
+    // log only once
+    expect(firstIndex === lastIndex).toBe(true)
+  })
+
   it('no warnings for image related link props', async () => {
     await renderViaHTTP(context.appPort, '/')
     expect(context.stderr).not.toContain('Warning: Invalid DOM property')

test/lib/next-test-utils.js

@@ -754,10 +754,10 @@ function runSuite(suiteName, context, options) {
   describe(`${suiteName} ${env}`, () => {
     beforeAll(async () => {
       options.beforeAll?.(env)
+      context.stdout = ''
       context.stderr = ''
-      const onStderr = (msg) => {
-        context.stderr += msg
-      }
+      const onStdout = (msg) => (context.stdout += msg)
+      const onStderr = (msg) => (context.stderr += msg)
       if (env === 'prod') {
         context.appPort = await findPort()
         const { stdout, stderr, code } = await nextBuild(appDir, [], {
@@ -768,11 +768,13 @@ function runSuite(suiteName, context, options) {
         context.stderr = stderr
         context.code = code
         context.server = await nextStart(context.appDir, context.appPort, {
+          onStdout,
           onStderr,
         })
       } else if (env === 'dev') {
         context.appPort = await findPort()
         context.server = await launchApp(context.appDir, context.appPort, {
+          onStdout,
           onStderr,
         })
       }