Fix revalidate for initial notFound: true paths (#28097)

This fixes revalidation not occurring correctly when `notFound: true` is returned during build, additional tests have been added to ensure this is working correctly for dynamic and non-dynamic pages returning `notFound: true` during build and then revalidating afterwards.  

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`

Fixes: #21453

packages/next/server/incremental-cache.ts

@@ -139,7 +139,12 @@ export class IncrementalCache {
     // let's check the disk for seed data
     if (!data) {
       if (this.prerenderManifest.notFoundRoutes.includes(pathname)) {
-        return { revalidateAfter: false, value: null }
+        const now = Date.now()
+        const revalidateAfter = this.calculateRevalidate(pathname, now)
+        data = {
+          value: null,
+          revalidateAfter: revalidateAfter !== false ? now : false,
+        }
       }
 
       try {

packages/next/server/render.tsx

@@ -827,11 +827,6 @@ export async function renderToHTML(
         ;(data as any).revalidate = false
       }
 
-      // this must come after revalidate is attached
-      if ((renderOpts as any).isNotFound) {
-        return null
-      }
-
       props.pageProps = Object.assign(
         {},
         props.pageProps,
@@ -843,6 +838,11 @@ export async function renderToHTML(
       ;(renderOpts as any).revalidate =
         'revalidate' in data ? data.revalidate : undefined
       ;(renderOpts as any).pageData = props
+
+      // this must come after revalidate is added to renderOpts
+      if ((renderOpts as any).isNotFound) {
+        return null
+      }
     }
 
     if (getServerSideProps) {

test/integration/not-found-revalidate/data.txt

@@ -0,0 +1 @@
+404

test/integration/not-found-revalidate/pages/404.js

@@ -8,6 +8,7 @@ export default function Page(props) {
 }
 
 export const getStaticProps = () => {
+  console.log('404 getStaticProps')
   return {
     props: {
       notFound: true,

test/integration/not-found-revalidate/pages/initial-not-found/[slug].js

@@ -0,0 +1,28 @@
+import fs from 'fs'
+import path from 'path'
+
+export async function getStaticProps() {
+  const data = await fs.promises.readFile(
+    path.join(process.cwd(), 'data.txt'),
+    'utf8'
+  )
+
+  console.log('revalidate', { data })
+
+  return {
+    props: { data },
+    notFound: data.trim() === '404',
+    revalidate: 1,
+  }
+}
+
+export async function getStaticPaths() {
+  return {
+    paths: [{ params: { slug: 'first' } }],
+    fallback: 'blocking',
+  }
+}
+
+export default function Page({ data }) {
+  return <p id="data">{data}</p>
+}

test/integration/not-found-revalidate/pages/initial-not-found/index.js

@@ -0,0 +1,21 @@
+import fs from 'fs'
+import path from 'path'
+
+export async function getStaticProps() {
+  const data = await fs.promises.readFile(
+    path.join(process.cwd(), 'data.txt'),
+    'utf8'
+  )
+
+  console.log('revalidate', { data })
+
+  return {
+    props: { data },
+    notFound: data.trim() === '404',
+    revalidate: 1,
+  }
+}
+
+export default function Page({ data }) {
+  return <p id="data">{data}</p>
+}

test/integration/not-found-revalidate/test/index.test.js

@@ -10,14 +10,74 @@ import {
   killApp,
   fetchViaHTTP,
   waitFor,
+  check,
 } from 'next-test-utils'
 
 jest.setTimeout(1000 * 60 * 2)
 const appDir = join(__dirname, '..')
+const dataFile = join(appDir, 'data.txt')
+
 let app
 let appPort
 
 const runTests = () => {
+  it('should revalidate page when notFund returned during build', async () => {
+    let res = await fetchViaHTTP(appPort, '/initial-not-found/first')
+    let $ = cheerio.load(await res.text())
+    expect(res.status).toBe(404)
+    expect($('#not-found').text()).toBe('404 page')
+
+    res = await fetchViaHTTP(appPort, '/initial-not-found/second')
+    $ = cheerio.load(await res.text())
+    expect(res.status).toBe(404)
+    expect($('#not-found').text()).toBe('404 page')
+
+    res = await fetchViaHTTP(appPort, '/initial-not-found')
+    $ = cheerio.load(await res.text())
+    expect(res.status).toBe(404)
+    expect($('#not-found').text()).toBe('404 page')
+
+    await fs.writeFile(dataFile, '200')
+
+    // wait for revalidation period
+    await waitFor(1500)
+    await fetchViaHTTP(appPort, '/initial-not-found/first')
+    await fetchViaHTTP(appPort, '/initial-not-found/second')
+    await fetchViaHTTP(appPort, '/initial-not-found')
+
+    // wait for revalidation to occur in background
+    try {
+      await check(async () => {
+        res = await fetchViaHTTP(appPort, '/initial-not-found/first')
+        $ = cheerio.load(await res.text())
+
+        return res.status === 200 && $('#data').text() === '200'
+          ? 'success'
+          : `${res.status} - ${$('#data').text()}`
+      }, 'success')
+
+      await check(async () => {
+        res = await fetchViaHTTP(appPort, '/initial-not-found/second')
+        $ = cheerio.load(await res.text())
+
+        return res.status === 200 && $('#data').text() === '200'
+          ? 'success'
+          : `${res.status} - ${$('#data').text()}`
+      }, 'success')
+
+      await check(async () => {
+        res = await fetchViaHTTP(appPort, '/initial-not-found')
+        $ = cheerio.load(await res.text())
+
+        return res.status === 200 && $('#data').text() === '200'
+          ? 'success'
+          : `${res.status} - ${$('#data').text()}`
+      }, 'success')
+    } finally {
+      await fs.writeFile(dataFile, '404')
+    }
+  })
+
   it('should revalidate after notFound is returned for fallback: blocking', async () => {
     let res = await fetchViaHTTP(appPort, '/fallback-blocking/hello')
     let $ = cheerio.load(await res.text())
@@ -138,9 +198,13 @@ describe('SSG notFound revalidate', () => {
   describe('production mode', () => {
     beforeAll(async () => {
       await fs.remove(join(appDir, '.next'))
-      await nextBuild(appDir)
+      await nextBuild(appDir, undefined, {
+        cwd: appDir,
+      })
       appPort = await findPort()
-      app = await nextStart(appDir, appPort)
+      app = await nextStart(appDir, appPort, {
+        cwd: appDir,
+      })
     })
     afterAll(() => killApp(app))