fix: don't set permanent caching header when res.revalidate() was used

src/run/headers.ts

@@ -266,7 +266,8 @@ export const setCacheControlHeaders = (
     ['GET', 'HEAD'].includes(request.method) &&
     !headers.has('cdn-cache-control') &&
     !headers.has('netlify-cdn-cache-control') &&
-    requestContext.usedFsReadForNonFallback
+    requestContext.usedFsReadForNonFallback &&
+    !requestContext.didPagesRouterOnDemandRevalidate
   ) {
     // handle CDN Cache Control on static files
     headers.set('cache-control', 'public, max-age=0, must-revalidate')

tests/e2e/page-router.test.ts

@@ -590,6 +590,21 @@ test.describe('Simple Page Router (no basePath, no i18n)', () => {
       'getStaticProps duration should not be longer than 10 seconds',
     ).toBeLessThan(10_000)
   })
+
+  test('API route calling res.revalidate() on page returning notFound: true is not cacheable', async ({
+    page,
+    pageRouter,
+  }) => {
+    // note: known conditions for problematic case is
+    // 1. API route needs to call res.revalidate()
+    // 2. revalidated page's getStaticProps must return notFound: true
+    const response = await page.goto(
+      new URL('/api/revalidate?path=/static/not-found', pageRouter.url).href,
+    )
+
+    expect(response?.status()).toEqual(200)
+    expect(response?.headers()['netlify-cdn-cache-control'] ?? '').not.toMatch(/(s-maxage|max-age)/)
+  })
 })
 
 test.describe('Page Router with basePath and i18n', () => {