tests

lubieowoce · lubieowoce · commit f00e3792d7bd · 2025-12-02T14:07:47.000+01:00
diff --git a/test/development/app-dir/cache-components-reused-promise/app/layout.tsx b/test/development/app-dir/cache-components-reused-promise/app/layout.tsx
@@ -0,0 +1,7 @@
+export default async function Layout({ children }) {
+  return (
+    <html>
+      <body>{children}</body>
+    </html>
+  )
+}
diff --git a/test/development/app-dir/cache-components-reused-promise/app/page.tsx b/test/development/app-dir/cache-components-reused-promise/app/page.tsx
@@ -0,0 +1,71 @@
+// This repros a bug from https://github.com/vercel/next.js/issues/86662.
+// The bug from occurs if we have:
+// - a cache (which requires warming = a restart in dev)
+// - a dynamic function (blocked until the dynamic stage, like an uncached fetch)
+//   that dedupes concurrent calls. note that that's not quite the same as caching it,
+//   because it gets dropped after finishing.
+
+import { Suspense } from 'react'
+
+export default async function Page() {
+  return (
+    <main>
+      <Suspense fallback={<div>Loading...</div>}>
+        <div id="random">
+          <DynamicRandom />
+        </div>
+      </Suspense>
+    </main>
+  )
+}
+
+async function DynamicRandom() {
+  const [, random] = await Promise.all([
+    // ensure that there's a restart to warm this cache.
+    cached(),
+    // This fetch going to be blocked on the dynamic stage.
+    // That promise should be rejected when restarting.
+    // If it's not rejected (like it wasn't before the fix),
+    // it'll remain hanging, and we'll never render anything.
+    fetchDynamicRandomDeduped(),
+  ])
+  return random
+}
+
+function dedupeConcurrent<T>(func: () => Promise<T>): () => Promise<T> {
+  let pending: Promise<T> | null = null
+  return () => {
+    if (pending !== null) {
+      console.log('dedupe :: re-using pending promise')
+      return pending
+    }
+
+    console.log('dedupe :: starting')
+    const promise = func()
+    pending = promise
+
+    const clearPending = () => {
+      console.log('dedupe :: finished')
+      pending = null
+    }
+    promise.then(clearPending, clearPending)
+
+    return promise
+  }
+}
+
+const fetchDynamicRandomDeduped = dedupeConcurrent(async () => {
+  const res = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random'
+  )
+  if (!res.ok) {
+    throw new Error(`request failed with status ${res.status}`)
+  }
+  const text = await res.text()
+  return text
+})
+
+async function cached() {
+  'use cache'
+  await new Promise((resolve) => setTimeout(resolve))
+}
diff --git a/test/development/app-dir/cache-components-reused-promise/cache-components-reused-promise.test.ts b/test/development/app-dir/cache-components-reused-promise/cache-components-reused-promise.test.ts
@@ -0,0 +1,12 @@
+import { nextTestSetup } from 'e2e-utils'
+
+describe('cache-components-dev-warmup - reused promise', () => {
+  const { next } = nextTestSetup({
+    files: __dirname,
+  })
+
+  it('aborts dynamic promises when restarting the render', async () => {
+    const browser = await next.browser('/')
+    expect(await browser.elementByCss('#random').text()).toMatch(/\d+\.\d+/)
+  })
+})
diff --git a/test/development/app-dir/cache-components-reused-promise/next.config.ts b/test/development/app-dir/cache-components-reused-promise/next.config.ts
@@ -0,0 +1,7 @@
+import type { NextConfig } from 'next'
+
+const nextConfig: NextConfig = {
+  cacheComponents: true,
+}
+
+export default nextConfig
