Add vary header to fix incorrectly caching RSC as HTML response (#41479)

Add failing test for the back button download bug. Created it as a new app given that adding it to the existing `app` suite did not reproduce the issue for some reason. The underlying reason is that we need to add `Vary: __rsc__, __next_router_prefetch__` to ensure Chrome does not cache the response and serve it on back button. The download was caused by the `application/octet-stream` content type, but that was just a consequence of serving the wrong response.  ## Bug - [ ] Related issues linked using `fixes #number` - [ ] Integration tests added - [ ] Errors have a helpful link attached, see `contributing.md` ## Feature - [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR. - [ ] Related issues linked using `fixes #number` - [ ] Integration tests added - [ ] Documentation added - [ ] Telemetry added. In case of a feature if it's used or not. - [ ] Errors have a helpful link attached, see `contributing.md` ## Documentation / Examples - [ ] Make sure the linting passes by running `pnpm lint` - [ ] The "examples guidelines" are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md) Co-authored-by: JJ Kasper <jj@jjsweb.site>
vercel · Oct 18, 2022 · c5896f2 · c5896f2
1 parent 6101bf6
commit c5896f2
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Showing 8 changed files with 106 additions and 2 deletions.
diff --git a/packages/next/server/base-server.ts b/packages/next/server/base-server.ts
@@ -1054,8 +1054,13 @@ export default abstract class Server<ServerOptions extends Options = Options> {
       ) &&
       (isSSG || hasServerProps)
 
-    if (isAppPath && req.headers['__rsc__']) {
-      if (isSSG) {
+    if (isAppPath) {
+      res.setHeader(
+        'vary',
+        '__rsc__, __next_router_state_tree__, __next_router_prefetch__'
+      )
+
+      if (isSSG && req.headers['__rsc__']) {
         isDataReq = true
         // strip header so we generate HTML still
         if (

diff --git a/test/e2e/app-dir/back-button-download-bug.test.ts b/test/e2e/app-dir/back-button-download-bug.test.ts
@@ -0,0 +1,45 @@
+import { createNext, FileRef } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import path from 'path'
+import webdriver from 'next-webdriver'
+
+describe('app-dir back button download bug', () => {
+  if ((global as any).isNextDeploy) {
+    it('should skip next deploy for now', () => {})
+    return
+  }
+
+  if (process.env.NEXT_TEST_REACT_VERSION === '^17') {
+    it('should skip for react v17', () => {})
+    return
+  }
+  let next: NextInstance
+
+  beforeAll(async () => {
+    next = await createNext({
+      files: new FileRef(path.join(__dirname, 'back-button-download-bug')),
+      dependencies: {
+        react: 'experimental',
+        'react-dom': 'experimental',
+      },
+      skipStart: true,
+    })
+
+    await next.start()
+  })
+  afterAll(() => next.destroy())
+
+  it('should redirect route when clicking link', async () => {
+    const browser = await webdriver(next.url, '/')
+    const text = await browser
+      .elementByCss('#to-post-1')
+      .click()
+      .waitForElementByCss('#post-page')
+      .text()
+    expect(text).toBe('This is the post page')
+
+    await browser.back()
+
+    expect(await browser.waitForElementByCss('#home-page').text()).toBe('Home!')
+  })
+})
diff --git a/test/e2e/app-dir/back-button-download-bug/app/layout.js b/test/e2e/app-dir/back-button-download-bug/app/layout.js
@@ -0,0 +1,8 @@
+export default function RootLayout({ children }) {
+  return (
+    <html lang="en">
+      <head></head>
+      <body>{children}</body>
+    </html>
+  )
+}
diff --git a/test/e2e/app-dir/back-button-download-bug/app/page.js b/test/e2e/app-dir/back-button-download-bug/app/page.js
@@ -0,0 +1,13 @@
+import Link from 'next/link'
+
+export default function Home() {
+  return (
+    <>
+      <h1 id="home-page">Home!</h1>
+      <Link href="/post/1">
+        <a id="to-post-1">To post 1</a>
+      </Link>
+      <Link href="/">To /</Link>
+    </>
+  )
+}
diff --git a/test/e2e/app-dir/back-button-download-bug/next.config.js b/test/e2e/app-dir/back-button-download-bug/next.config.js
@@ -0,0 +1,10 @@
+/** @type {import('next').NextConfig} */
+module.exports = {
+  reactStrictMode: true,
+  experimental: {
+    appDir: true,
+  },
+  images: {
+    domains: ['res.cloudinary.com', 'avatars.githubusercontent.com'],
+  },
+}
diff --git a/test/e2e/app-dir/back-button-download-bug/pages/_app.js b/test/e2e/app-dir/back-button-download-bug/pages/_app.js
@@ -0,0 +1,3 @@
+export default function MyApp({ Component, pageProps }) {
+  return <Component {...pageProps} />
+}
diff --git a/test/e2e/app-dir/back-button-download-bug/pages/_document.js b/test/e2e/app-dir/back-button-download-bug/pages/_document.js
@@ -0,0 +1,17 @@
+import Document, { Head, Html, Main, NextScript } from 'next/document'
+
+class MyDocument extends Document {
+  render() {
+    return (
+      <Html lang="en">
+        <Head />
+        <body>
+          <Main />
+          <NextScript />
+        </body>
+      </Html>
+    )
+  }
+}
+
+export default MyDocument
diff --git a/test/e2e/app-dir/back-button-download-bug/pages/post/[id]/index.js b/test/e2e/app-dir/back-button-download-bug/pages/post/[id]/index.js
@@ -0,0 +1,3 @@
+export default function Post() {
+  return <h1 id="post-page">This is the post page</h1>
+}