Fix notFound status code with ISR in app (#55542)

This ensures we properly set/restore the status code with ISR paths in
app router so that when we set the 404 status code with `notFound` it is
persisted properly.

Fixes: #43831
Closes: #48342
x-ref:
#49387 (comment)

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

@@ -2238,6 +2238,7 @@ export default abstract class Server<ServerOptions extends Options = Options> {
           html: result,
           pageData: metadata.pageData,
           headers,
+          status: isAppPath ? res.statusCode : undefined,
         },
         revalidate: metadata.revalidate,
       }
@@ -2493,6 +2494,10 @@ export default abstract class Server<ServerOptions extends Options = Options> {
           )
         }
 
+        if (cachedData.status) {
+          res.statusCode = cachedData.status
+        }
+
         return {
           type: isDataReq ? 'rsc' : 'html',
           body: isDataReq

test/e2e/app-dir/app-static/app-static.test.ts

@@ -700,6 +700,10 @@ createNextDescribe(
             'variable-revalidate-edge/post-method-request/page_client-reference-manifest.js',
             'partial-gen-params-no-additional-lang/[lang]/[slug]/page_client-reference-manifest.js',
             'partial-gen-params-no-additional-slug/[lang]/[slug]/page_client-reference-manifest.js',
+            'articles/[slug]/page.js',
+            'articles/[slug]/page_client-reference-manifest.js',
+            'articles/works.html',
+            'articles/works.rsc',
           ].sort()
         )
       })
@@ -752,6 +756,22 @@ createNextDescribe(
               "initialRevalidateSeconds": false,
               "srcRoute": "/",
             },
+            "/articles/works": Object {
+              "dataRoute": "/articles/works.rsc",
+              "experimentalBypassFor": Array [
+                Object {
+                  "key": "Next-Action",
+                  "type": "header",
+                },
+                Object {
+                  "key": "content-type",
+                  "type": "header",
+                  "value": "multipart/form-data",
+                },
+              ],
+              "initialRevalidateSeconds": 1,
+              "srcRoute": "/articles/[slug]",
+            },
             "/blog/seb": Object {
               "dataRoute": "/blog/seb.rsc",
               "experimentalBypassFor": Array [
@@ -1404,6 +1424,23 @@ createNextDescribe(
         `)
         expect(curManifest.dynamicRoutes).toMatchInlineSnapshot(`
           Object {
+            "/articles/[slug]": Object {
+              "dataRoute": "/articles/[slug].rsc",
+              "dataRouteRegex": "^\\\\/articles\\\\/([^\\\\/]+?)\\\\.rsc$",
+              "experimentalBypassFor": Array [
+                Object {
+                  "key": "Next-Action",
+                  "type": "header",
+                },
+                Object {
+                  "key": "content-type",
+                  "type": "header",
+                  "value": "multipart/form-data",
+                },
+              ],
+              "fallback": null,
+              "routeRegex": "^\\\\/articles\\\\/([^\\\\/]+?)(?:\\\\/)?$",
+            },
             "/blog/[author]": Object {
               "dataRoute": "/blog/[author].rsc",
               "dataRouteRegex": "^\\\\/blog\\\\/([^\\\\/]+?)\\\\.rsc$",
@@ -1590,6 +1627,15 @@ createNextDescribe(
       })
     }
 
+    it('should correctly handle statusCode with notFound + ISR', async () => {
+      for (let i = 0; i < 5; i++) {
+        const res = await next.fetch('/articles/non-existent')
+        expect(res.status).toBe(404)
+        expect(await res.text()).toContain('This page could not be found')
+        await waitFor(500)
+      }
+    })
+
     it('should cache correctly for fetchCache = default-cache', async () => {
       const res = await next.fetch('/default-cache')
       expect(res.status).toBe(200)

test/e2e/app-dir/app-static/app/articles/[slug]/page.tsx

@@ -0,0 +1,29 @@
+import { notFound } from 'next/navigation'
+
+export interface Props {
+  params: {
+    slug: string
+  }
+}
+
+const Article = ({ params }: Props) => {
+  const { slug } = params
+
+  if (slug !== 'works') {
+    return notFound()
+  }
+  return <div>Articles page with slug</div>
+}
+
+export const revalidate = 1
+export const dynamicParams = true
+
+export async function generateStaticParams() {
+  return [
+    {
+      slug: 'works', // Anything not this should be a 404 with no ISR
+    },
+  ]
+}
+
+export default Article