test(rsc): test React.cache (#668)

Co-authored-by: Hiroshi Ogawa <[email protected]>

Author: Copilot

packages/plugin-rsc/e2e/basic.test.ts

@@ -1006,4 +1006,17 @@ function defineTest(f: Fixture) {
       'test-browser-only: loading...',
     )
   })
+
+  test('React.cache', async ({ page }) => {
+    await page.goto(f.url())
+    await waitForHydration(page)
+    await page.getByRole('link', { name: 'test-react-cache' }).click()
+    await expect(page.getByTestId('test-react-cache-result')).toHaveText(
+      '(cacheFnCount = 2, nonCacheFnCount = 3)',
+    )
+    await page.reload()
+    await expect(page.getByTestId('test-react-cache-result')).toHaveText(
+      '(cacheFnCount = 4, nonCacheFnCount = 6)',
+    )
+  })
 }

packages/plugin-rsc/examples/basic/src/routes/react-cache/server.tsx

@@ -0,0 +1,45 @@
+import React from 'react'
+
+// Note that `React.cache` doesn't have effect inside action
+// since it's outside of RSC render request context.
+// https://github.com/hi-ogawa/reproductions/tree/main/next-rsc-action-cache
+
+export async function TestReactCache(props: { url: URL }) {
+  if (props.url.searchParams.has('test-react-cache')) {
+    await Promise.all([
+      testCacheFn('test1'),
+      testCacheFn('test2'),
+      testCacheFn('test1'),
+      testNonCacheFn('test1'),
+      testNonCacheFn('test2'),
+      testNonCacheFn('test1'),
+    ])
+  } else {
+    cacheFnCount = 0
+    nonCacheFnCount = 0
+  }
+
+  return (
+    <div data-testid="test-react-cache">
+      <a href="?test-react-cache">test-react-cache</a>{' '}
+      <span data-testid="test-react-cache-result">
+        (cacheFnCount = {cacheFnCount}, nonCacheFnCount = {nonCacheFnCount})
+      </span>
+    </div>
+  )
+}
+
+let cacheFnCount = 0
+let nonCacheFnCount = 0
+
+const testCacheFn = React.cache(async (...args: unknown[]) => {
+  console.log('[cached:args]', args)
+  cacheFnCount++
+  await new Promise((resolve) => setTimeout(resolve, 20))
+})
+
+const testNonCacheFn = async (...args: unknown[]) => {
+  console.log('[not-cached:args]', args)
+  nonCacheFnCount++
+  await new Promise((resolve) => setTimeout(resolve, 20))
+}

packages/plugin-rsc/examples/basic/src/routes/root.tsx

@@ -27,6 +27,7 @@ import { TestTailwindClient } from './tailwind/client'
 import { TestTailwindServer } from './tailwind/server'
 import { TestTemporaryReference } from './temporary-reference/client'
 import { TestUseCache } from './use-cache/server'
+import { TestReactCache } from './react-cache/server'
 import { TestHydrationMismatch } from './hydration-mismatch/server'
 import { TestBrowserOnly } from './browser-only/client'
 import { TestTransitiveCjsClient } from './deps/transitive-cjs/client'
@@ -75,6 +76,7 @@ export function Root(props: { url: URL }) {
         <TestModuleInvalidationServer />
         <TestBrowserOnly />
         <TestUseCache />
+        <TestReactCache url={props.url} />
       </body>
     </html>
   )