Make sure 404 pages do not get cached by a CDN when using next start

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

@@ -347,7 +347,7 @@ export function getPageHandler(ctx: ServerlessHandlerCtx) {
                 poweredByHeader,
               },
               {
-                private: isPreviewMode,
+                private: isPreviewMode || renderOpts.isNotFound,
                 stateful: !!getServerSideProps,
                 revalidate: renderOpts.revalidate,
               }
@@ -388,7 +388,7 @@ export function getPageHandler(ctx: ServerlessHandlerCtx) {
                 poweredByHeader,
               },
               {
-                private: isPreviewMode,
+                private: isPreviewMode || renderOpts.isNotFound,
                 stateful: !!getServerSideProps,
                 revalidate: renderOpts.revalidate,
               }

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

@@ -1610,7 +1610,8 @@ export default class Server {
 
       const revalidateOptions = !this.renderOpts.dev
         ? {
-            private: isPreviewMode,
+            // When the page is 404 cache-control should not be added
+            private: isPreviewMode || Boolean(cachedData.isNotFound),
             stateful: false, // GSP response
             revalidate:
               cachedData.curRevalidate !== undefined
@@ -1838,7 +1839,7 @@ export default class Server {
     const revalidateOptions =
       !this.renderOpts.dev || (hasServerProps && !isDataReq)
         ? {
-            private: isPreviewMode,
+            private: isPreviewMode || isNotFound,
             stateful: !isSSG,
             revalidate: sprRevalidate,
           }

test/integration/404-page/test/index.test.js

@@ -108,6 +108,44 @@ describe('404 Page Support', () => {
     runTests('serverless')
   })
 
+  it('should revalidate for custom 404 page while stale with ssg', async () => {
+    await fs.move(pages404, `${pages404}.bak`)
+    await fs.writeFile(
+      pages404,
+      `
+      const page = () => 'custom 404 page'
+      export async function getStaticProps() { return { props: {} } }
+      export default page
+    `
+    )
+    appPort = await findPort()
+    await nextBuild(appDir)
+    app = await nextStart(appDir, appPort)
+    const swrCacheControl = `s-maxage=31536000, stale-while-revalidate`
+    const res404 = await fetchViaHTTP(appPort, '/404')
+    const resNext = await fetchViaHTTP(appPort, '/_next/abc')
+    await fs.remove(pages404)
+    await fs.move(`${pages404}.bak`, pages404)
+    await killApp(app)
+
+    expect(res404.headers.get('Cache-Control')).toBe(swrCacheControl)
+    expect(resNext.headers.get('Cache-Control')).toBe(swrCacheControl)
+  })
+
+  it('should revalidate for custom 404 page without ssg', async () => {
+    appPort = await findPort()
+    await nextBuild(appDir)
+    app = await nextStart(appDir, appPort)
+    const res404 = await fetchViaHTTP(appPort, '/404')
+    const resNext = await fetchViaHTTP(appPort, '/_next/abc')
+
+    expect(res404.headers.get('Cache-Control')).toBe(null)
+    expect(resNext.headers.get('Cache-Control')).toBe(
+      'no-cache, no-store, max-age=0, must-revalidate'
+    )
+    await killApp(app)
+  })
+
   it('falls back to _error correctly without pages/404', async () => {
     await fs.move(pages404, `${pages404}.bak`)
     appPort = await findPort()