fix: apply permanent cdn-cache-control for fully static page (#274)

* fix: apply permanent cdn-cache-control for fully static page

* test: update headers.test.ts

* test: add integration and e2e test case

* test: update assertion after adding new page

Author: pieh

src/run/handlers/request-context.cts

@@ -3,6 +3,7 @@ import { AsyncLocalStorage } from 'node:async_hooks'
 export type RequestContext = {
   responseCacheGetLastModified?: number
   responseCacheKey?: string
+  usedFsRead?: boolean
 }
 
 type RequestContextAsyncLocalStorage = AsyncLocalStorage<RequestContext>

src/run/handlers/server.ts

@@ -82,7 +82,7 @@ export default async (request: Request) => {
 
     await adjustDateHeader({ headers: response.headers, request, span, tracer, requestContext })
 
-    setCacheControlHeaders(response.headers, request)
+    setCacheControlHeaders(response.headers, request, requestContext)
     setCacheTagsHeaders(response.headers, request, tagsManifest)
     setVaryHeaders(response.headers, request, nextConfig)
     setCacheStatusHeader(response.headers)

src/run/headers.test.ts

@@ -146,16 +146,35 @@ describe('headers', () => {
   describe('setCacheControlHeaders', () => {
     const defaultUrl = 'https://example.com'
 
-    test('should not set any headers if "cache-control" is not set', () => {
+    test('should not set any headers if "cache-control" is not set and "requestContext.usedFsRead" is not truthy', () => {
       const headers = new Headers()
       const request = new Request(defaultUrl)
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenCalledTimes(0)
     })
 
+    test('should set permanent "netlify-cdn-cache-control" if "cache-control" is not set and "requestContext.usedFsRead" is truthy', () => {
+      const headers = new Headers()
+      const request = new Request(defaultUrl)
+      vi.spyOn(headers, 'set')
+
+      setCacheControlHeaders(headers, request, { usedFsRead: true })
+
+      expect(headers.set).toHaveBeenNthCalledWith(
+        1,
+        'cache-control',
+        'public, max-age=0, must-revalidate',
+      )
+      expect(headers.set).toHaveBeenNthCalledWith(
+        2,
+        'netlify-cdn-cache-control',
+        'max-age=31536000',
+      )
+    })
+
     test('should not set any headers if "cache-control" is set and "cdn-cache-control" is present', () => {
       const givenHeaders = {
         'cache-control': 'public, max-age=0, must-revalidate',
@@ -165,7 +184,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl)
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenCalledTimes(0)
     })
@@ -179,7 +198,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl)
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenCalledTimes(0)
     })
@@ -192,7 +211,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl)
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenNthCalledWith(
         1,
@@ -214,7 +233,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl, { method: 'HEAD' })
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenNthCalledWith(
         1,
@@ -236,7 +255,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl, { method: 'POST' })
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenCalledTimes(0)
     })
@@ -249,7 +268,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl)
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenNthCalledWith(1, 'cache-control', 'public')
       expect(headers.set).toHaveBeenNthCalledWith(
@@ -267,7 +286,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl)
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenNthCalledWith(1, 'cache-control', 'max-age=604800')
       expect(headers.set).toHaveBeenNthCalledWith(
@@ -285,7 +304,7 @@ describe('headers', () => {
       const request = new Request(defaultUrl)
       vi.spyOn(headers, 'set')
 
-      setCacheControlHeaders(headers, request)
+      setCacheControlHeaders(headers, request, {})
 
       expect(headers.set).toHaveBeenNthCalledWith(
         1,

src/run/headers.ts

@@ -174,7 +174,11 @@ export const adjustDateHeader = async ({
  * Ensure stale-while-revalidate and s-maxage don't leak to the client, but
  * assume the user knows what they are doing if CDN cache controls are set
  */
-export const setCacheControlHeaders = (headers: Headers, request: Request) => {
+export const setCacheControlHeaders = (
+  headers: Headers,
+  request: Request,
+  requestContext: RequestContext,
+) => {
   const cacheControl = headers.get('cache-control')
   if (
     cacheControl !== null &&
@@ -197,6 +201,16 @@ export const setCacheControlHeaders = (headers: Headers, request: Request) => {
     headers.set('cache-control', browserCacheControl || 'public, max-age=0, must-revalidate')
     headers.set('netlify-cdn-cache-control', cdnCacheControl)
   }
+
+  if (
+    cacheControl === null &&
+    !headers.has('cdn-cache-control') &&
+    !headers.has('netlify-cdn-cache-control') &&
+    requestContext.usedFsRead
+  ) {
+    headers.set('cache-control', 'public, max-age=0, must-revalidate')
+    headers.set('netlify-cdn-cache-control', `max-age=31536000`)
+  }
 }
 
 export const setCacheTagsHeaders = (headers: Headers, request: Request, manifest: TagsManifest) => {

src/run/next.cts

@@ -7,6 +7,8 @@ import { trace } from '@opentelemetry/api'
 import { patchFs } from 'fs-monkey'
 import type { getRequestHandlers } from 'next/dist/server/lib/start-server.js'
 
+import { getRequestContext } from './handlers/request-context.cjs'
+
 type FS = typeof import('fs')
 
 const fetchBeforeNextPatchedIt = globalThis.fetch
@@ -31,6 +33,11 @@ export async function getMockedRequestHandlers(...args: Parameters<typeof getReq
           const relPath = relative(resolve('.next/server/pages'), path)
           const file = await store.get(await encodeBlobKey(relPath))
           if (file !== null) {
+            const requestContext = getRequestContext()
+            if (requestContext) {
+              requestContext.usedFsRead = true
+            }
+
             return file
           }
         }

tests/e2e/page-router.test.ts

@@ -79,9 +79,15 @@ test('requesting a non existing page route that needs to be fetched from the blo
   pageRouter,
 }) => {
   const response = await page.goto(new URL('non-exisitng', pageRouter.url).href)
+  const headers = response?.headers() || {}
   expect(response?.status()).toBe(404)
 
   expect(await page.textContent('h1')).toBe('404')
+
+  expect(headers['netlify-cdn-cache-control']).toBe(
+    'no-cache, no-store, max-age=0, must-revalidate',
+  )
+  expect(headers['cache-control']).toBe('no-cache,no-store,max-age=0,must-revalidate')
 })
 
 test('requesting a page with a very long name works', async ({ page, pageRouter }) => {
@@ -165,3 +171,11 @@ test('unstable-cache should work', async ({ pageRouter }) => {
     return 'success'
   }, 'success')
 })
+
+test('Fully static pages should be cached permanently', async ({ page, pageRouter }) => {
+  const response = await page.goto(new URL('static/fully-static', pageRouter.url).href)
+  const headers = response?.headers() || {}
+
+  expect(headers['netlify-cdn-cache-control']).toBe('max-age=31536000')
+  expect(headers['cache-control']).toBe('public,max-age=0,must-revalidate')
+})

tests/fixtures/page-router/pages/static/fully-static.js

@@ -0,0 +1,7 @@
+const FullyStatic = () => (
+  <div>
+    <p>This page is not using getStaticProps()</p>
+  </div>
+)
+
+export default FullyStatic

tests/integration/cache-handler.test.ts

@@ -49,6 +49,7 @@ describe('page router', () => {
       '/static/revalidate-slow',
       '404.html',
       '500.html',
+      'static/fully-static.html',
     ])
 
     // test the function call

tests/integration/page-router.test.ts

@@ -113,3 +113,15 @@ test<FixtureTestContext>('Should return JSON for data req to page route', async
 
   expect(data.pageProps.show).toBeDefined()
 })
+
+test<FixtureTestContext>('Should set permanent "netlify-cdn-cache-control" header on fully static pages"', async (ctx) => {
+  await createFixture('page-router', ctx)
+  await runPlugin(ctx)
+
+  const response = await invokeFunction(ctx, {
+    url: '/static/fully-static',
+  })
+
+  expect(response.headers?.['netlify-cdn-cache-control']).toBe('max-age=31536000')
+  expect(response.headers?.['cache-control']).toBe('public, max-age=0, must-revalidate')
+})

tests/integration/static.test.ts

@@ -45,6 +45,7 @@ test<FixtureTestContext>('requesting a non existing page route that needs to be
     '/static/revalidate-slow',
     '404.html',
     '500.html',
+    'static/fully-static.html',
     // the real key is much longer and ends in a hash, but we only assert on the first 50 chars to make it easier
   ])