Extend support of Pages router to React 18

vercel · Sep 18, 2024 · d2f3767 · d2f3767
1 parent 7d40d87
commit d2f3767
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Showing 20 changed files with 343 additions and 131 deletions.
diff --git a/.eslintrc.json b/.eslintrc.json
@@ -45,7 +45,11 @@
         "jest/no-conditional-expect": "off",
         "jest/valid-title": "off",
         "jest/no-interpolation-in-snapshots": "off",
-        "jest/no-export": "off"
+        "jest/no-export": "off",
+        "jest/no-standalone-expect": [
+          "error",
+          { "additionalTestBlockFunctions": ["gateReact18"] }
+        ]
       }
     },
     { "files": ["**/__tests__/**"], "env": { "jest": true } },

diff --git a/packages/next/package.json b/packages/next/package.json
@@ -108,8 +108,8 @@
     "@opentelemetry/api": "^1.1.0",
     "@playwright/test": "^1.41.2",
     "babel-plugin-react-compiler": "*",
-    "react": "19.0.0-rc-a99d8e8d-20240916",
-    "react-dom": "19.0.0-rc-a99d8e8d-20240916",
+    "react": "^18.2.0 || 19.0.0-rc-a99d8e8d-20240916",
+    "react-dom": "^18.2.0 || 19.0.0-rc-a99d8e8d-20240916",
     "sass": "^1.3.0"
   },
   "peerDependenciesMeta": {

diff --git a/packages/next/src/build/webpack-config.ts b/packages/next/src/build/webpack-config.ts
@@ -107,8 +107,8 @@ const NEXT_PROJECT_ROOT_DIST_CLIENT = path.join(
   'client'
 )
 
-if (parseInt(React.version) < 19) {
-  throw new Error('Next.js requires react >= 19.0.0 to be installed.')
+if (parseInt(React.version) < 18) {
+  throw new Error('Next.js requires react >= 18.2.0 to be installed.')
 }
 
 export const babelIncludeRegexes: RegExp[] = [

diff --git a/packages/next/src/client/legacy/image.tsx b/packages/next/src/client/legacy/image.tsx
@@ -9,6 +9,8 @@ import React, {
   useState,
   type JSX,
 } from 'react'
+import * as ReactDOM from 'react-dom'
+import Head from '../../shared/lib/head'
 import {
   imageConfigDefault,
   VALID_LOADERS,
@@ -26,6 +28,8 @@ function normalizeSrc(src: string): string {
   return src[0] === '/' ? src.slice(1) : src
 }
 
+const supportsFloat = typeof ReactDOM.preload === 'function'
+
 const configEnv = process.env.__NEXT_IMAGE_OPTS as any as ImageConfigComplete
 const loadedImageURLs = new Set<string>()
 const allImgs = new Map<
@@ -978,6 +982,20 @@ export default function Image({
     }
   }
 
+  const linkProps:
+    | React.DetailedHTMLProps<
+        React.LinkHTMLAttributes<HTMLLinkElement>,
+        HTMLLinkElement
+      >
+    | undefined = supportsFloat
+    ? undefined
+    : {
+        imageSrcSet: imgAttributes.srcSet,
+        imageSizes: imgAttributes.sizes,
+        crossOrigin: rest.crossOrigin,
+        referrerPolicy: rest.referrerPolicy,
+      }
+
   const useLayoutEffect =
     typeof window === 'undefined' ? React.useEffect : React.useLayoutEffect
   const onLoadingCompleteRef = useRef(onLoadingComplete)
@@ -1044,6 +1062,27 @@ export default function Image({
         ) : null}
         <ImageElement {...imgElementArgs} />
       </span>
+      {!supportsFloat && priority ? (
+        // Note how we omit the `href` attribute, as it would only be relevant
+        // for browsers that do not support `imagesrcset`, and in those cases
+        // it would likely cause the incorrect image to be preloaded.
+        //
+        // https://html.spec.whatwg.org/multipage/semantics.html#attr-link-imagesrcset
+        <Head>
+          <link
+            key={
+              '__nimg-' +
+              imgAttributes.src +
+              imgAttributes.srcSet +
+              imgAttributes.sizes
+            }
+            rel="preload"
+            as="image"
+            href={imgAttributes.srcSet ? undefined : imgAttributes.src}
+            {...linkProps}
+          />
+        </Head>
+      ) : null}
     </>
   )
 }
diff --git a/packages/next/src/client/use-merged-ref.ts b/packages/next/src/client/use-merged-ref.ts
@@ -1,29 +1,34 @@
-import { useMemo, type Ref } from 'react'
+import { useMemo, useRef, type Ref } from 'react'
 
+// This is a compatibility hook to support React 18 and 19 refs.
+// In 19, a cleanup function from refs may be returned.
+// In 18, returning a cleanup function creates a warning.
+// Since we take userspace refs, we don't know ahead of time if a cleanup function will be returned.
+// This implements cleanup functions with the old behavior in 18.
+// We know refs are always called alternating with `null` and then `T`.
+// So a call with `null` means we need to call the previous cleanup functions.
 export function useMergedRef<TElement>(
   refA: Ref<TElement>,
   refB: Ref<TElement>
 ): Ref<TElement> {
-  return useMemo(() => mergeRefs(refA, refB), [refA, refB])
-}
+  const cleanupA = useRef<() => void>(() => {})
+  const cleanupB = useRef<() => void>(() => {})
 
-export function mergeRefs<TElement>(
-  refA: Ref<TElement>,
-  refB: Ref<TElement>
-): Ref<TElement> {
-  if (!refA || !refB) {
-    return refA || refB
-  }
-
-  return (current: TElement) => {
-    const cleanupA = applyRef(refA, current)
-    const cleanupB = applyRef(refB, current)
+  return useMemo(() => {
+    if (!refA || !refB) {
+      return refA || refB
+    }
 
-    return () => {
-      cleanupA()
-      cleanupB()
+    return (current: TElement | null): void => {
+      if (current === null) {
+        cleanupA.current()
+        cleanupB.current()
+      } else {
+        cleanupA.current = applyRef(refA, current)
+        cleanupB.current = applyRef(refB, current)
+      }
     }
-  }
+  }, [refA, refB])
 }
 
 function applyRef<TElement>(

diff --git a/packages/next/src/server/render.tsx b/packages/next/src/server/render.tsx
@@ -40,7 +40,7 @@ import type { Revalidate, SwrDelta } from './lib/revalidate'
 import type { COMPILER_NAMES } from '../shared/lib/constants'
 
 import React, { type JSX } from 'react'
-import ReactDOMServerEdge from 'react-dom/server.edge'
+import ReactDOMServerBrowser from 'react-dom/server.browser'
 import { StyleRegistry, createStyleRegistry } from 'styled-jsx'
 import {
   GSP_NO_RETURNED_VALUE,
@@ -127,7 +127,8 @@ function noRouter() {
 }
 
 async function renderToString(element: React.ReactElement) {
-  const renderStream = await ReactDOMServerEdge.renderToReadableStream(element)
+  const renderStream =
+    await ReactDOMServerBrowser.renderToReadableStream(element)
   await renderStream.allReady
   return streamToString(renderStream)
 }
@@ -1326,7 +1327,7 @@ export async function renderToHTMLImpl(
     ) => {
       const content = renderContent(EnhancedApp, EnhancedComponent)
       return await renderToInitialFizzStream({
-        ReactDOMServer: ReactDOMServerEdge,
+        ReactDOMServer: ReactDOMServerBrowser,
         element: content,
       })
     }

diff --git a/packages/next/types/react-dom.d.ts b/packages/next/types/react-dom.d.ts
@@ -70,6 +70,10 @@ declare module 'react-dom/server.edge' {
   >
 }
 
+declare module 'react-dom/server.browser' {
+  export * from 'react-dom/server.edge'
+}
+
 declare module 'react-dom/static.edge' {
   import type { JSX } from 'react'
   /**

diff --git a/packages/next/webpack.config.js b/packages/next/webpack.config.js
@@ -13,6 +13,7 @@ const pagesExternals = [
   'react-dom/package.json',
   'react-dom/client',
   'react-dom/server',
+  'react-dom/server.browser',
   'react-dom/server.edge',
   'react-server-dom-webpack/client',
   'react-server-dom-webpack/client.edge',