Don't default reactRoot for 10.x

Author: devknoll

.github/workflows/test_react_experimental.yml

@@ -31,6 +31,7 @@ jobs:
       NEXT_TELEMETRY_DISABLED: 1
       HEADLESS: true
       NEXT_PRIVATE_SKIP_SIZE_TESTS: true
+      NEXT_PRIVATE_REACT_ROOT: 1
     strategy:
       fail-fast: false
       matrix:

packages/next/next-server/server/config-shared.ts

@@ -115,7 +115,7 @@ export const defaultConfig: NextConfig = {
     externalDir: false,
     serialWebpackBuild: false,
     turboMode: false,
-    reactRoot: false,
+    reactRoot: Number(process.env.NEXT_PRIVATE_REACT_ROOT) > 0,
   },
   future: {
     strictPostcssConfiguration: false,

packages/next/next-server/server/config.ts

@@ -9,7 +9,6 @@ import { defaultConfig, normalizeConfig } from './config-shared'
 import { loadWebpackHook } from './config-utils'
 import { ImageConfig, imageConfigDefault, VALID_LOADERS } from './image-config'
 import { loadEnvConfig } from '@next/env'
-import ReactDOM from 'react'
 
 export { DomainLocales, NextConfig, normalizeConfig } from './config-shared'
 
@@ -387,18 +386,6 @@ function assignDefaults(userConfig: { [key: string]: any }) {
     }
   }
 
-  if (
-    typeof userConfig.experimental?.reactRoot === 'undefined' &&
-    (typeof (ReactDOM as any).createRoot === 'function' ||
-      typeof (ReactDOM as any).unstable_createRoot === 'function')
-  ) {
-    console.warn(
-      chalk.yellow.bold('Warning: ') +
-        'The "reactRoot" option defaulted to "true" based on your version of React. Please update your next.config.js.'
-    )
-    result.experimental.reactRoot = true
-  }
-
   return result
 }