Add test to verify which pages are prerendered in use-cache test su…

…ite (vercel#75681)

This allows us to catch regressions and monitor progress (e.g. for NAR-85).

In addition, we're consolidating all pages in the test app to use a single root layout without a suspense boundary. Before we switched the app from using the `dynamicIO` flag to the `useCache` flag, some pages needed a suspense boundary to not fail the build.

test/e2e/app-dir/use-cache/app/(no-suspense)/[id]/page.tsx → test/e2e/app-dir/use-cache/app/[id]/page.tsx

@@ -4,7 +4,10 @@ async function getCachedRandom(n: number) {
 }
 
 export async function generateStaticParams() {
-  return [{ id: await getCachedRandom(10) }, { id: await getCachedRandom(2) }]
+  return [
+    { id: `a${await getCachedRandom(9)}` },
+    { id: `b${await getCachedRandom(2)}` },
+  ]
 }
 
 export default async function Page() {

test/e2e/app-dir/use-cache/app/(no-suspense)/imported-from-client/page.tsx → test/e2e/app-dir/use-cache/app/imported-from-client/page.tsx

@@ -1,7 +1,7 @@
 'use client'
 
 import { foo, bar, baz } from './cached'
-import { Form } from '../../form'
+import { Form } from '../form'
 
 export default function Page() {
   return <Form foo={foo} bar={bar} baz={baz} />

test/e2e/app-dir/use-cache/app/(suspense)/page.tsx → test/e2e/app-dir/use-cache/app/page.tsx

@@ -1,4 +1,4 @@
-import { Foo } from '../client'
+import { Foo } from './client'
 
 async function getCachedRandom(x: number, children: React.ReactNode) {
   'use cache'

test/e2e/app-dir/use-cache/app/(no-suspense)/passed-to-client/page.tsx → test/e2e/app-dir/use-cache/app/passed-to-client/page.tsx

@@ -1,4 +1,4 @@
-import { Form } from '../../form'
+import { Form } from '../form'
 
 function getRandomValue() {
   const v = Math.random()

test/e2e/app-dir/use-cache/next.config.js

@@ -3,6 +3,7 @@
  */
 const nextConfig = {
   experimental: {
+    ppr: process.env.__NEXT_EXPERIMENTAL_PPR === 'true',
     useCache: true,
     cacheLife: {
       frequent: {

test/e2e/app-dir/use-cache/use-cache.test.ts

@@ -277,6 +277,49 @@ describe('use-cache', () => {
   }
 
   if (isNextStart) {
+    it('should prerender fully cacheable pages as static HTML', async () => {
+      const prerenderManifest = JSON.parse(
+        await next.readFile('.next/prerender-manifest.json')
+      )
+
+      let prerenderedRoutes = Object.keys(prerenderManifest.routes).sort()
+
+      if (process.env.__NEXT_EXPERIMENTAL_PPR === 'true') {
+        // For the purpose of this test we don't consider an incomplete shell.
+        prerenderedRoutes = prerenderedRoutes.filter((route) => {
+          const filename = route.replace(/^\//, '').replace(/^$/, 'index')
+
+          return next
+            .readFileSync(`.next/server/app/${filename}.html`)
+            .endsWith('</html>')
+        })
+      }
+
+      expect(prerenderedRoutes).toEqual([
+        // [id] route, first entry in generateStaticParams
+        expect.stringMatching(/\/a\d/),
+        // [id] route, second entry in generateStaticParams
+        expect.stringMatching(/\/b\d/),
+        '/cache-fetch',
+        '/cache-fetch-no-store',
+        '/cache-life',
+        '/cache-tag',
+        // TODO(useCache): Should be prerendered when NAR-85 is fixed.
+        // '/form',
+        '/imported-from-client',
+        '/logs',
+        '/method-props',
+        // TODO(useCache): Should be prerendered when NAR-85 is fixed.
+        // '/not-found',
+        '/passed-to-client',
+        '/react-cache',
+        '/static-class-method',
+        '/use-action-state',
+        // TODO(useCache): Should be prerendered when NAR-85 is fixed.
+        // '/with-server-action',
+      ])
+    })
+
     it('should match the expected revalidate config on the prerender manifest', async () => {
       const prerenderManifest = JSON.parse(
         await next.readFile('.next/prerender-manifest.json')

test/lib/next-modes/base.ts

@@ -1,6 +1,6 @@
 import os from 'os'
 import path from 'path'
-import { existsSync, promises as fs, rmSync } from 'fs'
+import { existsSync, promises as fs, rmSync, readFileSync } from 'fs'
 import treeKill from 'tree-kill'
 import type { NextConfig } from 'next'
 import { FileRef, isNextDeploy } from '../e2e-utils'
@@ -521,6 +521,10 @@ export class NextInstance {
     return fs.readFile(path.join(this.testDir, filename), 'utf8')
   }
 
+  public readFileSync(filename: string) {
+    return readFileSync(path.join(this.testDir, filename), 'utf8')
+  }
+
   public async readJSON(filename: string) {
     return JSON.parse(
       await fs.readFile(path.join(this.testDir, filename), 'utf-8')