fix: set x-deployment-id to every middleware prefetch request (#71193)

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### What?

`x-deployment-id` is missing on prefetch requests

### Why?

To handle version skew on the pages router. When version skew is turned
on, `x-deployment-id` should be used on prefetch otherwise the server
will return 404. But with middleware enabled, the 404 does not appear to
hard-refresh the page.

### How?

next.js seems to be relying on the 404 to perform a _hard_ navigation
and auto-refresh the client. But that doesn't appear to happen when
middleware is in use (separate issue, not addressed in this PR), which
is causing the client to navigate to 404 whenever we deploy a new
version of the site to vercel.

instead of sending the client to 404, passing the `x-deployment-id`
helps guarantee that next-data requests respect version skew protection.

---------

Co-authored-by: JJ Kasper <[email protected]>

packages/next/src/shared/lib/router/router.ts

@@ -498,7 +498,10 @@ function fetchNextData({
       headers: Object.assign(
         {} as HeadersInit,
         isPrefetch ? { purpose: 'prefetch' } : {},
-        isPrefetch && hasMiddleware ? { 'x-middleware-prefetch': '1' } : {}
+        isPrefetch && hasMiddleware ? { 'x-middleware-prefetch': '1' } : {},
+        process.env.NEXT_DEPLOYMENT_ID
+          ? { 'x-deployment-id': process.env.NEXT_DEPLOYMENT_ID }
+          : {}
       ),
       method: params?.method ?? 'GET',
     })

test/production/deployment-id-handling/app/middleware.ts

@@ -0,0 +1,5 @@
+import { NextRequest, NextResponse } from 'next/server'
+
+export function middleware(_req: NextRequest) {
+  return NextResponse.next()
+}

test/production/deployment-id-handling/app/pages/index.tsx

@@ -1,13 +1,17 @@
 import testImage from '../public/test.jpg'
 import Image from 'next/image'
 import styles from './styles.module.css'
+import Link from 'next/link'
 
 export default function Page() {
   return (
     <>
       <p className={styles.template}>hello pages</p>
       <p id="deploymentId">{process.env.NEXT_DEPLOYMENT_ID}</p>
       <Image src={testImage} alt="test image" />
+      <Link href="/pages-edge" id="edge-link">
+        Edge
+      </Link>
 
       <button
         onClick={() => {

test/production/deployment-id-handling/app/pages/pages-edge.tsx

@@ -1,10 +1,10 @@
 import testImage from '../public/test.jpg'
 import Image from 'next/image'
 
-export default function Page() {
+export default function Page({ data }: { data: string }) {
   return (
     <>
-      <p>hello pages edge</p>
+      <h1>{data}</h1>
       <Image src={testImage} alt="test image" />
       <p id="deploymentId">{process.env.NEXT_DEPLOYMENT_ID}</p>
 
@@ -25,3 +25,11 @@ export default function Page() {
 export const config = {
   runtime: 'experimental-edge',
 }
+
+export function getServerSideProps() {
+  return {
+    props: {
+      data: 'hello pages edge',
+    },
+  }
+}

test/production/deployment-id-handling/deployment-id-handling.test.ts

@@ -84,6 +84,34 @@ describe.each(['NEXT_DEPLOYMENT_ID', 'CUSTOM_DEPLOYMENT_ID'])(
       }
     )
 
+    it('should contain deployment id in prefetch request', async () => {
+      const dataHeaders = []
+      const browser = await next.browser('/', {
+        beforePageLoad(page) {
+          page.on('request', async (req) => {
+            const headers = await req.allHeaders()
+            if (headers['x-nextjs-data']) {
+              dataHeaders.push(headers)
+            }
+          })
+        },
+      })
+
+      await browser.elementByCss('#edge-link').click()
+
+      await retry(async () => {
+        expect(await browser.elementByCss('h1').text()).toBe('hello pages edge')
+        expect(await browser.url()).toContain('/pages-edge')
+        expect(dataHeaders.length).toBeGreaterThan(0)
+      })
+
+      expect(
+        dataHeaders.every(
+          (headers) => headers['x-deployment-id'] === deploymentId
+        )
+      ).toBe(true)
+    })
+
     it('should contain deployment id in RSC payload request headers', async () => {
       const rscHeaders = []
       const browser = await next.browser('/from-app', {