fix(build): correct SSG classification for dynamic pages with generateStaticParams

wyattjoh · wyattjoh · commit 5a0e958d3408 · 2025-10-07T01:37:50.000-06:00
Pages with generateStaticParams that use dynamic APIs (cookies(), headers(), connection()) were incorrectly marked as SSG in build output. This caused users to mistakenly believe their pages were statically generated when they were actually rendered dynamically at request time. The bug occurred because the dynamic detection check ran before individual routes were processed. The check looked at the pattern route (e.g., /blog/[slug]) which was never actually rendered, causing it to return false. When the actual routes were processed later (e.g., /blog/post-1), they correctly detected revalidate: 0 but the parent page had already been marked as SSG. This fix adds a second check after processing all prerendered routes to correct the parent page classification if any routes turned out to be dynamic. Fixes #84584
diff --git a/packages/next/src/build/index.ts b/packages/next/src/build/index.ts
@@ -3279,6 +3279,17 @@ export default async function build(
               }
             }
 
+            // After processing all static prerendered routes, check if any had revalidate: 0
+            // and update the parent page accordingly. This handles the case where
+            // generateStaticParams was used but the routes turned out to be dynamic.
+            if (hasRevalidateZero && pageInfos.get(page)?.isSSG) {
+              pageInfos.set(page, {
+                ...(pageInfos.get(page) as PageInfo),
+                isStatic: false,
+                isSSG: false,
+              })
+            }
+
             if (!hasRevalidateZero && isDynamicRoute(page)) {
               // When PPR fallbacks aren't used, we need to include it here. If
               // they are enabled, then it'll already be included in the
diff --git a/test/production/app-dir/static-rendering-with-connection/app/blog/[slug]/page.tsx b/test/production/app-dir/static-rendering-with-connection/app/blog/[slug]/page.tsx
@@ -0,0 +1,16 @@
+import { connection } from 'next/server'
+
+export async function generateStaticParams() {
+  return [{ slug: 'slug-01' }, { slug: 'slug-02' }, { slug: 'slug-03' }]
+}
+
+export default async function Page({
+  params,
+}: {
+  params: Promise<{ slug: string }>
+}) {
+  await connection()
+  const { slug } = await params
+
+  return <div id="page">Page {slug}</div>
+}
diff --git a/test/production/app-dir/static-rendering-with-connection/app/layout.tsx b/test/production/app-dir/static-rendering-with-connection/app/layout.tsx
@@ -0,0 +1,11 @@
+import { ReactNode, Suspense } from 'react'
+
+export default function Root({ children }: { children: ReactNode }) {
+  return (
+    <html>
+      <body>
+        <Suspense>{children}</Suspense>
+      </body>
+    </html>
+  )
+}
diff --git a/test/production/app-dir/static-rendering-with-connection/static-rendering-with-connection.test.ts b/test/production/app-dir/static-rendering-with-connection/static-rendering-with-connection.test.ts
@@ -0,0 +1,89 @@
+import { nextTestSetup } from 'e2e-utils'
+
+describe('static-rendering-with-connection', () => {
+  const { next, isNextDeploy } = nextTestSetup({
+    files: __dirname,
+    skipStart: true,
+    skipDeployment: true,
+    env: {
+      __NEXT_PRIVATE_DETERMINISTIC_BUILD_OUTPUT: '1',
+    },
+  })
+
+  if (isNextDeploy) {
+    it.skip('should skip deployment', () => {})
+    return
+  }
+
+  beforeAll(async () => {
+    await next.build()
+  })
+
+  if (process.env.__NEXT_EXPERIMENTAL_CACHE_COMPONENTS === 'true') {
+    it('should mark routes with connection() as partial prerendered', async () => {
+      // When cache components are enabled, routes with connection() should be
+      // marked as partial prerendered.
+      expect(getTreeView(next.cliOutput)).toMatchInlineSnapshot(`
+       "Route (app)
+       ┌ ○ /_not-found
+       └ ◐ /blog/[slug]
+           ├ /blog/[slug]
+           ├ /blog/slug-01
+           ├ /blog/slug-02
+           └ /blog/slug-03
+
+
+       ○  (Static)             prerendered as static content
+       ◐  (Partial Prerender)  prerendered as static HTML with dynamic server-streamed content"
+      `)
+    })
+  } else {
+    it('should mark routes with connection() as dynamic, not SSG', async () => {
+      // Routes with generateStaticParams that use connection() should be marked as dynamic
+      // because connection() makes the page dynamic. This is a regression test for a bug
+      // where pages with generateStaticParams were incorrectly marked as SSG even when
+      // the individual routes used dynamic APIs.
+      expect(getTreeView(next.cliOutput)).toMatchInlineSnapshot(`
+            "Route (app)
+            ┌ ○ /_not-found
+            └ ƒ /blog/[slug]
+                ├ /blog/slug-01
+                ├ /blog/slug-02
+                └ /blog/slug-03
+
+
+            ○  (Static)   prerendered as static content
+            ƒ  (Dynamic)  server-rendered on demand"
+          `)
+    })
+  }
+
+  it('should render the blog pages correctly', async () => {
+    await next.start()
+
+    // Test one of the generated routes
+    const $ = await next.render$('/blog/slug-01')
+    expect($('#page').text()).toBe('Page slug-01')
+
+    await next.stop()
+  })
+})
+
+/**
+ * Extracts the route tree view from the build output.
+ * This captures everything from "Route " onwards to show the build output.
+ */
+function getTreeView(cliOutput: string): string {
+  let foundStart = false
+  const lines: string[] = []
+
+  for (const line of cliOutput.split('\n')) {
+    foundStart ||= line.startsWith('Route ')
+
+    if (foundStart) {
+      lines.push(line)
+    }
+  }
+
+  return lines.join('\n').trim()
+}
