Preview Mode Should Not Cache

packages/next/build/webpack/loaders/next-serverless-loader.ts

@@ -206,7 +206,8 @@ const nextServerlessLoader: loader.Loader = function() {
     }
     const {parse} = require('url')
     const {parse: parseQs} = require('querystring')
-    const {renderToHTML} =require('next/dist/next-server/server/render');
+    const {renderToHTML} = require('next/dist/next-server/server/render');
+    const { tryGetPreviewData } = require('next/dist/next-server/server/api-utils');
     const {sendHTML} = require('next/dist/next-server/server/send-html');
     const buildManifest = require('${buildManifest}');
     const reactLoadableManifest = require('${reactLoadableManifest}');
@@ -320,6 +321,9 @@ const nextServerlessLoader: loader.Loader = function() {
 
         const isFallback = parsedUrl.query.__nextFallback
 
+        const previewData = tryGetPreviewData(req, res, options.previewProps)
+        const isPreviewMode = previewData !== false
+
         let result = await renderToHTML(req, res, "${page}", Object.assign({}, unstable_getStaticProps ? {} : parsedUrl.query, nowParams ? nowParams : params, _params, isFallback ? { __nextFallback: 'true' } : {}), renderOpts)
 
         if (_nextData && !fromExport) {
@@ -329,12 +333,19 @@ const nextServerlessLoader: loader.Loader = function() {
 
           res.setHeader(
             'Cache-Control',
-            unstable_getServerProps
+            isPreviewMode
+              ? \`private, no-cache, no-store, max-age=0, must-revalidate\`
+              : unstable_getServerProps
               ? \`no-cache, no-store, must-revalidate\`
               : \`s-maxage=\${renderOpts.revalidate}, stale-while-revalidate\`
           )
           res.end(payload)
           return null
+        } else if (isPreviewMode) {
+          res.setHeader(
+            'Cache-Control',
+            'private, no-cache, no-store, max-age=0, must-revalidate'
+          )
         }
 
         if (fromExport) return { html: result, renderOpts }

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

@@ -821,20 +821,25 @@ export default class Server {
     res: ServerResponse,
     payload: any,
     type: string,
-    revalidate?: number | false
+    options?: { revalidate: number | false; private: boolean }
   ) {
     // TODO: ETag? Cache-Control headers? Next-specific headers?
     res.setHeader('Content-Type', type)
     res.setHeader('Content-Length', Buffer.byteLength(payload))
     if (!this.renderOpts.dev) {
-      if (revalidate) {
+      if (options?.private) {
         res.setHeader(
           'Cache-Control',
-          revalidate < 0
+          `private, no-cache, no-store, max-age=0, must-revalidate`
+        )
+      } else if (options?.revalidate) {
+        res.setHeader(
+          'Cache-Control',
+          options.revalidate < 0
             ? `no-cache, no-store, must-revalidate`
-            : `s-maxage=${revalidate}, stale-while-revalidate`
+            : `s-maxage=${options.revalidate}, stale-while-revalidate`
         )
-      } else if (revalidate === false) {
+      } else if (options?.revalidate === false) {
         res.setHeader(
           'Cache-Control',
           `s-maxage=31536000, stale-while-revalidate`
@@ -910,7 +915,10 @@ export default class Server {
             res,
             JSON.stringify(renderResult?.renderOpts?.pageData),
             'application/json',
-            -1
+            {
+              revalidate: -1,
+              private: false, // Leave to user-land caching
+            }
           )
           return null
         }
@@ -924,7 +932,10 @@ export default class Server {
           ...opts,
           isDataReq,
         })
-        this.__sendPayload(res, JSON.stringify(props), 'application/json', -1)
+        this.__sendPayload(res, JSON.stringify(props), 'application/json', {
+          revalidate: -1,
+          private: false, // Leave to user-land caching
+        })
         return null
       }
 
@@ -957,7 +968,9 @@ export default class Server {
         res,
         data,
         isDataReq ? 'application/json' : 'text/html; charset=utf-8',
-        cachedData.curRevalidate
+        cachedData.curRevalidate !== undefined
+          ? { revalidate: cachedData.curRevalidate, private: isPreviewMode }
+          : undefined
       )
 
       // Stop the request chain here if the data we sent was up-to-date
@@ -1064,7 +1077,7 @@ export default class Server {
         res,
         isDataReq ? JSON.stringify(pageData) : html,
         isDataReq ? 'application/json' : 'text/html; charset=utf-8',
-        sprRevalidate
+        { revalidate: sprRevalidate, private: isPreviewMode }
       )
     }
 

test/integration/prerender-preview/server.js

@@ -0,0 +1,41 @@
+const http = require('http')
+const url = require('url')
+const fs = require('fs')
+const path = require('path')
+const server = http.createServer((req, res) => {
+  let { pathname } = url.parse(req.url)
+  if (pathname.startsWith('/_next/data')) {
+    pathname = pathname
+      .replace(`/_next/data/${process.env.BUILD_ID}/`, '/')
+      .replace(/\.json$/, '')
+  }
+  console.log('serving', pathname)
+
+  if (pathname === '/favicon.ico') {
+    res.statusCode = 404
+    return res.end()
+  }
+
+  if (pathname.startsWith('/_next/static/')) {
+    res.write(
+      fs.readFileSync(
+        path.join(
+          __dirname,
+          './.next/static/',
+          pathname.slice('/_next/static/'.length)
+        ),
+        'utf8'
+      )
+    )
+    return res.end()
+  } else {
+    const re = require(`./.next/serverless/pages${pathname}`)
+    return typeof re.render === 'function'
+      ? re.render(req, res)
+      : re.default(req, res)
+  }
+})
+
+server.listen(process.env.PORT, () => {
+  console.log('ready on', process.env.PORT)
+})

test/integration/prerender-preview/test/index.test.js

@@ -6,6 +6,7 @@ import fs from 'fs-extra'
 import {
   fetchViaHTTP,
   findPort,
+  initNextServerScript,
   killApp,
   nextBuild,
   nextStart,
@@ -20,14 +21,18 @@ jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 2
 const appDir = join(__dirname, '..')
 const nextConfigPath = join(appDir, 'next.config.js')
 
+async function getBuildId() {
+  return fs.readFile(join(appDir, '.next', 'BUILD_ID'), 'utf8')
+}
+
 function getData(html) {
   const $ = cheerio.load(html)
   const nextData = $('#__NEXT_DATA__')
   const preEl = $('#props-pre')
   return { nextData: JSON.parse(nextData.html()), pre: preEl.text() }
 }
 
-function runTests() {
+function runTests(startServer = nextStart) {
   it('should compile successfully', async () => {
     await fs.remove(join(appDir, '.next'))
     const { code, stdout } = await nextBuild(appDir, [], {
@@ -40,7 +45,7 @@ function runTests() {
   let appPort, app
   it('should start production application', async () => {
     appPort = await findPort()
-    app = await nextStart(appDir, appPort)
+    app = await startServer(appDir, appPort)
   })
 
   it('should return prerendered page on first request', async () => {
@@ -91,10 +96,33 @@ function runTests() {
     const html = await res.text()
 
     const { nextData, pre } = getData(html)
+    expect(res.headers.get('cache-control')).toBe(
+      'private, no-cache, no-store, max-age=0, must-revalidate'
+    )
     expect(nextData).toMatchObject({ isFallback: false })
     expect(pre).toBe('true and {"lets":"goooo"}')
   })
 
+  it('should return correct caching headers for data preview request', async () => {
+    const res = await fetchViaHTTP(
+      appPort,
+      `/_next/data/${encodeURI(await getBuildId())}/index.json`,
+      {},
+      { headers: { Cookie: previewCookieString } }
+    )
+    const json = await res.json()
+
+    expect(res.headers.get('cache-control')).toBe(
+      'private, no-cache, no-store, max-age=0, must-revalidate'
+    )
+    expect(json).toMatchObject({
+      pageProps: {
+        preview: true,
+        previewData: { lets: 'goooo' },
+      },
+    })
+  })
+
   it('should return cookies to be expired on reset request', async () => {
     const res = await fetchViaHTTP(
       appPort,
@@ -162,6 +190,16 @@ function runTests() {
   })
 }
 
+const startServerlessEmulator = async (dir, port) => {
+  const scriptPath = join(dir, 'server.js')
+  const env = Object.assign(
+    {},
+    { ...process.env },
+    { PORT: port, BUILD_ID: await getBuildId() }
+  )
+  return initNextServerScript(scriptPath, /ready on/i, env)
+}
+
 describe('Prerender Preview Mode', () => {
   describe('Server Mode', () => {
     beforeAll(async () => {
@@ -170,6 +208,7 @@ describe('Prerender Preview Mode', () => {
 
     runTests()
   })
+
   describe('Serverless Mode', () => {
     beforeAll(async () => {
       await fs.writeFile(
@@ -183,4 +222,18 @@ describe('Prerender Preview Mode', () => {
 
     runTests()
   })
+
+  describe('Emulated Serverless Mode', () => {
+    beforeAll(async () => {
+      await fs.writeFile(
+        nextConfigPath,
+        `module.exports = { target: 'experimental-serverless-trace' }` + os.EOL
+      )
+    })
+    afterAll(async () => {
+      await fs.remove(nextConfigPath)
+    })
+
+    runTests(startServerlessEmulator)
+  })
 })