Ensure unstable_revalidate does not error from notFound: true

packages/next/server/api-utils/node.ts

@@ -315,7 +315,13 @@ async function unstable_revalidate(
       },
     })
 
-    if (!res.ok) {
+    // we use the cache header to determine successful revalidate as
+    // a non-200 status code can be returned from a successful revalidate
+    // e.g. notFound: true returns 404 status code but is successful
+    const cacheHeader =
+      res.headers.get('x-vercel-cache') || res.headers.get('x-nextjs-cache')
+
+    if (cacheHeader?.toUpperCase() !== 'REVALIDATED') {
       throw new Error(`Invalid response ${res.status}`)
     }
   } catch (err) {

packages/next/server/base-server.ts

@@ -1528,6 +1528,21 @@ export default abstract class Server {
       return null
     }
 
+    if (isSSG) {
+      // set x-nextjs-cache header to match the header
+      // we set for the image-optimizer
+      res.setHeader(
+        'x-nextjs-cache',
+        isManualRevalidate
+          ? 'REVALIDATED'
+          : cacheEntry.isMiss
+          ? 'MISS'
+          : cacheEntry.isStale
+          ? 'STALE'
+          : 'HIT'
+      )
+    }
+
     const { revalidate, value: cachedData } = cacheEntry
     const revalidateOptions: any =
       typeof revalidate !== 'undefined' &&

test/e2e/prerender.test.ts

@@ -149,6 +149,11 @@ describe('Prerender', () => {
       initialRevalidateSeconds: false,
       srcRoute: '/api-docs/[...slug]',
     },
+    '/blocking-fallback-once/404-on-manual-revalidate': {
+      dataRoute: `/_next/data/${next.buildId}/blocking-fallback-once/404-on-manual-revalidate.json`,
+      initialRevalidateSeconds: false,
+      srcRoute: '/blocking-fallback-once/[slug]',
+    },
     '/blocking-fallback-some/a': {
       dataRoute: `/_next/data/${next.buildId}/blocking-fallback-some/a.json`,
       initialRevalidateSeconds: 1,
@@ -1978,6 +1983,44 @@ describe('Prerender', () => {
         expect($4('#time').text()).not.toBe(initialTime)
       })
 
+      it('should manual revalidate that returns notFound: true', async () => {
+        const html = await renderViaHTTP(
+          next.url,
+          '/blocking-fallback-once/404-on-manual-revalidate'
+        )
+        const $ = cheerio.load(html)
+        const initialTime = $('#time').text()
+
+        expect($('p').text()).toMatch(/Post:.*?404-on-manual-revalidate/)
+
+        const html2 = await renderViaHTTP(
+          next.url,
+          '/blocking-fallback-once/404-on-manual-revalidate'
+        )
+        const $2 = cheerio.load(html2)
+
+        expect(initialTime).toBe($2('#time').text())
+
+        const res = await fetchViaHTTP(
+          next.url,
+          '/api/manual-revalidate',
+          {
+            pathname: '/blocking-fallback-once/404-on-manual-revalidate',
+          },
+          { redirect: 'manual' }
+        )
+        expect(res.status).toBe(200)
+        const revalidateData = await res.json()
+        expect(revalidateData.revalidated).toBe(true)
+
+        const res2 = await fetchViaHTTP(
+          next.url,
+          '/blocking-fallback-once/404-on-manual-revalidate'
+        )
+        expect(res2.status).toBe(404)
+        expect(await res2.text()).toContain('This page could not be found')
+      })
+
       it('should handle manual revalidate for fallback: false', async () => {
         const res = await fetchViaHTTP(
           next.url,

test/e2e/prerender/pages/blocking-fallback-once/[slug].js

@@ -4,14 +4,26 @@ import { useRouter } from 'next/router'
 
 export async function getStaticPaths() {
   return {
-    paths: [],
+    paths: [
+      {
+        params: { slug: '404-on-manual-revalidate' },
+      },
+    ],
     fallback: 'blocking',
   }
 }
 
 export async function getStaticProps({ params }) {
   await new Promise((resolve) => setTimeout(resolve, 1000))
 
+  if (process.env.NEXT_PHASE !== 'phase-production-build') {
+    if (params.slug === '404-on-manual-revalidate') {
+      return {
+        notFound: true,
+      }
+    }
+  }
+
   return {
     props: {
       params,