fix: added cache control headers for static app routes (#72521)

This pull request includes several changes to improve cache control
handling and add new test cases for verifying cache headers in the
standalone mode of the application.

Improvements to cache control handling:

*
[`packages/next/src/server/base-server.ts`](diffhunk://#diff-6f4291cc2bfc5073fdca12a014011769e840ee68583db1468acef075f037015aL3295-R3298):
Updated cache control conditions to check for `undefined` explicitly
before setting cache headers.
[[1]](diffhunk://#diff-6f4291cc2bfc5073fdca12a014011769e840ee68583db1468acef075f037015aL3295-R3298)
[[2]](diffhunk://#diff-6f4291cc2bfc5073fdca12a014011769e840ee68583db1468acef075f037015aL3318-R3324)
[[3]](diffhunk://#diff-6f4291cc2bfc5073fdca12a014011769e840ee68583db1468acef075f037015aR3354-R3365)

New test cases:

*
[`test/production/standalone-mode/required-server-files/required-server-files-app.test.ts`](diffhunk://#diff-0d083b6c7bd3a8a3e9c5ee854123ada3b72db58220d8b65912b047b082f834a2R104-R129):
Added test cases to verify that the correct cache headers are sent for
app routes and app pages.

New static and dynamic route handlers:

*
`test/production/standalone-mode/required-server-files/app/api/test/[slug]/route.js`:
Added a new dynamic route handler with forced static generation.
([test/production/standalone-mode/required-server-files/app/api/test/[slug]/route.jsR1-R7](diffhunk://#diff-1cf8a2cfdbb6473656b2456af0267556270fbbaa7ee2c37e2f3e6c6fed1e4d21R1-R7))
*
`test/production/standalone-mode/required-server-files/app/test/[slug]/page.jsx`:
Added a new static page with a revalidation interval and a function to
generate static parameters.
([test/production/standalone-mode/required-server-files/app/test/[slug]/page.jsxR1-R9](diffhunk://#diff-32038443ca3e4f28db37a6543966397682c64cf6f34e6dd03fd8096414d23022R1-R9))

- Fixes #65814

Co-authored-by: Janka Uryga <[email protected]>
Co-authored-by: Sam Ko <[email protected]>

packages/next/src/server/base-server.ts

@@ -3292,7 +3292,10 @@ export default abstract class Server<
 
       // 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')) {
+      if (
+        typeof cacheEntry.revalidate !== 'undefined' &&
+        !res.getHeader('Cache-Control')
+      ) {
         res.setHeader(
           'Cache-Control',
           formatRevalidate({
@@ -3315,7 +3318,10 @@ export default abstract class Server<
     } else if (cachedData.kind === CachedRouteKind.REDIRECT) {
       // 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')) {
+      if (
+        typeof cacheEntry.revalidate !== 'undefined' &&
+        !res.getHeader('Cache-Control')
+      ) {
         res.setHeader(
           'Cache-Control',
           formatRevalidate({
@@ -3339,17 +3345,33 @@ export default abstract class Server<
         return null
       }
     } else if (cachedData.kind === CachedRouteKind.APP_ROUTE) {
-      const headers = { ...cachedData.headers }
+      const headers = fromNodeOutgoingHttpHeaders(cachedData.headers)
 
       if (!(this.minimalMode && isSSG)) {
-        delete headers[NEXT_CACHE_TAGS_HEADER]
+        headers.delete(NEXT_CACHE_TAGS_HEADER)
+      }
+
+      // 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 cacheEntry.revalidate !== 'undefined' &&
+        !res.getHeader('Cache-Control') &&
+        !headers.get('Cache-Control')
+      ) {
+        headers.set(
+          'Cache-Control',
+          formatRevalidate({
+            revalidate: cacheEntry.revalidate,
+            expireTime: this.nextConfig.expireTime,
+          })
+        )
       }
 
       await sendResponse(
         req,
         res,
         new Response(cachedData.body, {
-          headers: fromNodeOutgoingHttpHeaders(headers),
+          headers,
           status: cachedData.status || 200,
         })
       )

test/production/standalone-mode/required-server-files/app/api/test/[slug]/route.js

@@ -0,0 +1,7 @@
+export const dynamic = 'force-static'
+
+export async function GET(request, context) {
+  const { params } = context
+  const { slug } = params
+  return Response.json({ message: `Hello, ${slug}!` })
+}

test/production/standalone-mode/required-server-files/app/test/[slug]/page.jsx

@@ -0,0 +1,9 @@
+export const revalidate = 3600
+
+export default function Page() {
+  return <div>Hello, World!</div>
+}
+
+export async function generateStaticParams() {
+  return []
+}

test/production/standalone-mode/required-server-files/required-server-files-app.test.ts

@@ -101,6 +101,32 @@ describe('required server files app router', () => {
     if (server) await killApp(server)
   })
 
+  it('should send the right cache headers for an app route', async () => {
+    const res = await fetchViaHTTP(appPort, '/api/test/123', undefined, {
+      headers: {
+        'x-matched-path': '/api/test/[slug]',
+        'x-now-route-matches': '1=123&nxtPslug=123',
+      },
+    })
+    expect(res.status).toBe(200)
+    expect(res.headers.get('cache-control')).toBe(
+      's-maxage=31536000, stale-while-revalidate'
+    )
+  })
+
+  it('should send the right cache headers for an app page', async () => {
+    const res = await fetchViaHTTP(appPort, '/test/123', undefined, {
+      headers: {
+        'x-matched-path': '/test/[slug]',
+        'x-now-route-matches': '1=123&nxtPslug=123',
+      },
+    })
+    expect(res.status).toBe(200)
+    expect(res.headers.get('cache-control')).toBe(
+      's-maxage=3600, stale-while-revalidate'
+    )
+  })
+
   it('should not fail caching', async () => {
     expect(next.cliOutput).not.toContain('ERR_INVALID_URL')
   })

test/turbopack-build-tests-manifest.json

@@ -16578,6 +16578,8 @@
     "test/production/standalone-mode/required-server-files/required-server-files-app.test.ts": {
       "passed": [],
       "failed": [
+        "required server files app router should send the right cache headers for an app route",
+        "required server files app router should send the right cache headers for an app page",
         "required server files app router should not fail caching",
         "required server files app router should not send cache tags in minimal mode for SSR",
         "required server files app router should not send invalid soft tags to cache handler",