From 24647b9a3a6f0b914423c95a59cd6fcc81caa778 Mon Sep 17 00:00:00 2001
From: JJ Kasper <jj@jjsweb.site>
Date: Mon, 9 Sep 2024 12:58:07 -0700
Subject: [PATCH] Add ability to customize Cache-Control (#69802)

This continues https://github.com/vercel/next.js/pull/39707 bringing the
changes up to date with canary and adds test cases to ensure it's
working as expected.

Closes: https://github.com/vercel/next.js/issues/22319
Closes: https://github.com/vercel/next.js/pull/39707
Closes: NDX-148
---
 packages/next/src/server/base-server.ts       | 17 +++-
 packages/next/src/server/lib/router-server.ts |  2 +-
 packages/next/src/server/send-payload.ts      |  4 +-
 .../app/app-ssg/[slug]/page.tsx               | 18 ++++
 .../custom-cache-control/app/app-ssr/page.tsx |  9 ++
 .../custom-cache-control/app/layout.tsx       |  8 ++
 .../custom-cache-control.test.ts              | 84 +++++++++++++++++++
 .../custom-cache-control/next.config.js       | 74 ++++++++++++++++
 .../pages/pages-auto-static.tsx               |  7 ++
 .../pages/pages-ssg/[slug].tsx                | 29 +++++++
 .../custom-cache-control/pages/pages-ssr.tsx  | 15 ++++
 test/integration/404-page/test/index.test.js  |  4 +-
 .../pages-dir/production/test/index.test.ts   |  2 +-
 13 files changed, 266 insertions(+), 7 deletions(-)
 create mode 100644 test/e2e/app-dir/custom-cache-control/app/app-ssg/[slug]/page.tsx
 create mode 100644 test/e2e/app-dir/custom-cache-control/app/app-ssr/page.tsx
 create mode 100644 test/e2e/app-dir/custom-cache-control/app/layout.tsx
 create mode 100644 test/e2e/app-dir/custom-cache-control/custom-cache-control.test.ts
 create mode 100644 test/e2e/app-dir/custom-cache-control/next.config.js
 create mode 100644 test/e2e/app-dir/custom-cache-control/pages/pages-auto-static.tsx
 create mode 100644 test/e2e/app-dir/custom-cache-control/pages/pages-ssg/[slug].tsx
 create mode 100644 test/e2e/app-dir/custom-cache-control/pages/pages-ssr.tsx

diff --git a/packages/next/src/server/base-server.ts b/packages/next/src/server/base-server.ts
index 42819826ea5a6..8aed8efebec90 100644
--- a/packages/next/src/server/base-server.ts
+++ b/packages/next/src/server/base-server.ts
@@ -2587,6 +2587,13 @@ export default abstract class Server<ServerOptions extends Options = Options> {
       }
     )
 
+    if (isPreviewMode) {
+      res.setHeader(
+        'Cache-Control',
+        'private, no-cache, no-store, max-age=0, must-revalidate'
+      )
+    }
+
     if (!cacheEntry) {
       if (ssgCacheKey && !(isOnDemandRevalidate && revalidateOnlyGenerated)) {
         // A cache entry might not be generated if a response is written
@@ -2719,7 +2726,9 @@ export default abstract class Server<ServerOptions extends Options = Options> {
       // for the revalidate value
       addRequestMeta(req, 'notFoundRevalidate', cacheEntry.revalidate)
 
-      if (cacheEntry.revalidate) {
+      // If cache control is already set on the response we don't
+      // override it to allow users to customize it via next.config
+      if (cacheEntry.revalidate && !res.getHeader('Cache-Control')) {
         res.setHeader(
           'Cache-Control',
           formatRevalidate({
@@ -2740,7 +2749,9 @@ export default abstract class Server<ServerOptions extends Options = Options> {
       await this.render404(req, res, { pathname, query }, false)
       return null
     } else if (cachedData.kind === 'REDIRECT') {
-      if (cacheEntry.revalidate) {
+      // If cache control is already set on the response we don't
+      // override it to allow users to customize it via next.config
+      if (cacheEntry.revalidate && !res.getHeader('Cache-Control')) {
         res.setHeader(
           'Cache-Control',
           formatRevalidate({
@@ -3223,7 +3234,7 @@ export default abstract class Server<ServerOptions extends Options = Options> {
     if (setHeaders) {
       res.setHeader(
         'Cache-Control',
-        'no-cache, no-store, max-age=0, must-revalidate'
+        'private, no-cache, no-store, max-age=0, must-revalidate'
       )
     }
 
diff --git a/packages/next/src/server/lib/router-server.ts b/packages/next/src/server/lib/router-server.ts
index 4757b7b0aba6a..37c87d3aa2f96 100644
--- a/packages/next/src/server/lib/router-server.ts
+++ b/packages/next/src/server/lib/router-server.ts
@@ -526,7 +526,7 @@ export async function initialize(opts: {
       // 404 case
       res.setHeader(
         'Cache-Control',
-        'no-cache, no-store, max-age=0, must-revalidate'
+        'private, no-cache, no-store, max-age=0, must-revalidate'
       )
 
       // Short-circuit favicon.ico serving so that the 404 page doesn't get built as favicon is requested by the browser when loading any route.
diff --git a/packages/next/src/server/send-payload.ts b/packages/next/src/server/send-payload.ts
index e79c33f8a0b01..de5a45ec1aadf 100644
--- a/packages/next/src/server/send-payload.ts
+++ b/packages/next/src/server/send-payload.ts
@@ -59,7 +59,9 @@ export async function sendRenderResult({
     res.setHeader('X-Powered-By', 'Next.js')
   }
 
-  if (typeof revalidate !== 'undefined') {
+  // If cache control is already set on the response we don't
+  // override it to allow users to customize it via next.config
+  if (typeof revalidate !== 'undefined' && !res.getHeader('Cache-Control')) {
     res.setHeader(
       'Cache-Control',
       formatRevalidate({
diff --git a/test/e2e/app-dir/custom-cache-control/app/app-ssg/[slug]/page.tsx b/test/e2e/app-dir/custom-cache-control/app/app-ssg/[slug]/page.tsx
new file mode 100644
index 0000000000000..70eb489bb26b9
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/app/app-ssg/[slug]/page.tsx
@@ -0,0 +1,18 @@
+export const revalidate = 120
+
+export function generateStaticParams() {
+  return [
+    {
+      slug: 'first',
+    },
+  ]
+}
+
+export default function Page({ params }) {
+  return (
+    <>
+      <p>/app-ssg/[slug]</p>
+      <p>{JSON.stringify(params)}</p>
+    </>
+  )
+}
diff --git a/test/e2e/app-dir/custom-cache-control/app/app-ssr/page.tsx b/test/e2e/app-dir/custom-cache-control/app/app-ssr/page.tsx
new file mode 100644
index 0000000000000..69d3c4b3c18fe
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/app/app-ssr/page.tsx
@@ -0,0 +1,9 @@
+export const dynamic = 'force-dynamic'
+
+export default function Page() {
+  return (
+    <>
+      <p>/app-ssr</p>
+    </>
+  )
+}
diff --git a/test/e2e/app-dir/custom-cache-control/app/layout.tsx b/test/e2e/app-dir/custom-cache-control/app/layout.tsx
new file mode 100644
index 0000000000000..888614deda3ba
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/app/layout.tsx
@@ -0,0 +1,8 @@
+import { ReactNode } from 'react'
+export default function Root({ children }: { children: ReactNode }) {
+  return (
+    <html>
+      <body>{children}</body>
+    </html>
+  )
+}
diff --git a/test/e2e/app-dir/custom-cache-control/custom-cache-control.test.ts b/test/e2e/app-dir/custom-cache-control/custom-cache-control.test.ts
new file mode 100644
index 0000000000000..dce7b40eb0b80
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/custom-cache-control.test.ts
@@ -0,0 +1,84 @@
+import { nextTestSetup } from 'e2e-utils'
+
+describe('custom-cache-control', () => {
+  const { next, isNextDev, isNextDeploy } = nextTestSetup({
+    files: __dirname,
+  })
+
+  if (isNextDeploy) {
+    // customizing these headers won't apply on environments
+    // where headers are applied outside of the Next.js server
+    it('should skip for deploy', () => {})
+    return
+  }
+
+  it('should have custom cache-control for app-ssg prerendered', async () => {
+    const res = await next.fetch('/app-ssg/first')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev ? 'no-store, must-revalidate' : 's-maxage=30'
+    )
+  })
+
+  it('should have custom cache-control for app-ssg lazy', async () => {
+    const res = await next.fetch('/app-ssg/lazy')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev ? 'no-store, must-revalidate' : 's-maxage=31'
+    )
+  })
+  ;(process.env.__NEXT_EXPERIMENTAL_PPR ? it.skip : it)(
+    'should have default cache-control for app-ssg another',
+    async () => {
+      const res = await next.fetch('/app-ssg/another')
+      // eslint-disable-next-line jest/no-standalone-expect
+      expect(res.headers.get('cache-control')).toBe(
+        isNextDev
+          ? 'no-store, must-revalidate'
+          : 's-maxage=120, stale-while-revalidate'
+      )
+    }
+  )
+
+  it('should have custom cache-control for app-ssr', async () => {
+    const res = await next.fetch('/app-ssr')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev ? 'no-store, must-revalidate' : 's-maxage=32'
+    )
+  })
+
+  it('should have custom cache-control for auto static page', async () => {
+    const res = await next.fetch('/pages-auto-static')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev ? 'no-store, must-revalidate' : 's-maxage=33'
+    )
+  })
+
+  it('should have custom cache-control for pages-ssg prerendered', async () => {
+    const res = await next.fetch('/pages-ssg/first')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev ? 'no-store, must-revalidate' : 's-maxage=34'
+    )
+  })
+
+  it('should have custom cache-control for pages-ssg lazy', async () => {
+    const res = await next.fetch('/pages-ssg/lazy')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev ? 'no-store, must-revalidate' : 's-maxage=35'
+    )
+  })
+
+  it('should have default cache-control for pages-ssg another', async () => {
+    const res = await next.fetch('/pages-ssg/another')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev
+        ? 'no-store, must-revalidate'
+        : 's-maxage=120, stale-while-revalidate'
+    )
+  })
+
+  it('should have default cache-control for pages-ssr', async () => {
+    const res = await next.fetch('/pages-ssr')
+    expect(res.headers.get('cache-control')).toBe(
+      isNextDev ? 'no-store, must-revalidate' : 's-maxage=36'
+    )
+  })
+})
diff --git a/test/e2e/app-dir/custom-cache-control/next.config.js b/test/e2e/app-dir/custom-cache-control/next.config.js
new file mode 100644
index 0000000000000..7a61bbe7e6723
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/next.config.js
@@ -0,0 +1,74 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+const nextConfig = {
+  headers() {
+    return [
+      {
+        source: '/app-ssg/first',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 's-maxage=30',
+          },
+        ],
+      },
+      {
+        source: '/app-ssg/lazy',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 's-maxage=31',
+          },
+        ],
+      },
+      {
+        source: '/app-ssr',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 's-maxage=32',
+          },
+        ],
+      },
+      {
+        source: '/pages-auto-static',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 's-maxage=33',
+          },
+        ],
+      },
+      {
+        source: '/pages-ssg/first',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 's-maxage=34',
+          },
+        ],
+      },
+      {
+        source: '/pages-ssg/lazy',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 's-maxage=35',
+          },
+        ],
+      },
+      {
+        source: '/pages-ssr',
+        headers: [
+          {
+            key: 'Cache-Control',
+            value: 's-maxage=36',
+          },
+        ],
+      },
+    ]
+  },
+}
+
+module.exports = nextConfig
diff --git a/test/e2e/app-dir/custom-cache-control/pages/pages-auto-static.tsx b/test/e2e/app-dir/custom-cache-control/pages/pages-auto-static.tsx
new file mode 100644
index 0000000000000..97f19eff92600
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/pages/pages-auto-static.tsx
@@ -0,0 +1,7 @@
+export default function Page() {
+  return (
+    <>
+      <p>/pages-auto-static</p>
+    </>
+  )
+}
diff --git a/test/e2e/app-dir/custom-cache-control/pages/pages-ssg/[slug].tsx b/test/e2e/app-dir/custom-cache-control/pages/pages-ssg/[slug].tsx
new file mode 100644
index 0000000000000..9b9c4d0182f75
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/pages/pages-ssg/[slug].tsx
@@ -0,0 +1,29 @@
+export function getStaticProps({ params }) {
+  return {
+    props: {
+      now: Date.now(),
+      params,
+    },
+    revalidate: 120,
+  }
+}
+
+export function getStaticPaths() {
+  return {
+    paths: [
+      {
+        params: { slug: 'first' },
+      },
+    ],
+    fallback: 'blocking',
+  }
+}
+
+export default function Page({ params }) {
+  return (
+    <>
+      <p>/pages-ssg/[slug]</p>
+      <p>{JSON.stringify(params)}</p>
+    </>
+  )
+}
diff --git a/test/e2e/app-dir/custom-cache-control/pages/pages-ssr.tsx b/test/e2e/app-dir/custom-cache-control/pages/pages-ssr.tsx
new file mode 100644
index 0000000000000..5792abd592c3e
--- /dev/null
+++ b/test/e2e/app-dir/custom-cache-control/pages/pages-ssr.tsx
@@ -0,0 +1,15 @@
+export function getServerSideProps() {
+  return {
+    props: {
+      now: Date.now(),
+    },
+  }
+}
+
+export default function Page() {
+  return (
+    <>
+      <p>/pages-ssr</p>
+    </>
+  )
+}
diff --git a/test/integration/404-page/test/index.test.js b/test/integration/404-page/test/index.test.js
index ca76076108567..5a59b227ee1eb 100644
--- a/test/integration/404-page/test/index.test.js
+++ b/test/integration/404-page/test/index.test.js
@@ -262,7 +262,9 @@ describe('404 Page Support', () => {
         await killApp(app)
 
         expect(cache404).toBe(null)
-        expect(cacheNext).toBe('no-cache, no-store, max-age=0, must-revalidate')
+        expect(cacheNext).toBe(
+          'private, no-cache, no-store, max-age=0, must-revalidate'
+        )
       })
 
       it('shows error with getInitialProps in pages/404 build', async () => {
diff --git a/test/production/pages-dir/production/test/index.test.ts b/test/production/pages-dir/production/test/index.test.ts
index 8b70938940196..95441526fdd12 100644
--- a/test/production/pages-dir/production/test/index.test.ts
+++ b/test/production/pages-dir/production/test/index.test.ts
@@ -618,7 +618,7 @@ createNextDescribe(
 
         expect(res.status).toBe(404)
         expect(res.headers.get('Cache-Control')).toBe(
-          'no-cache, no-store, max-age=0, must-revalidate'
+          'private, no-cache, no-store, max-age=0, must-revalidate'
         )
       })