fix(plugin-rsc): cjs to esm interop helper doesn't handle native/external cjs import properly

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

@@ -1523,6 +1523,14 @@ function defineTest(f: Fixture) {
     ).toHaveText('ok:browser')
   })
 
+  test('cjs builtin interop', async ({ page }) => {
+    await page.goto(f.url())
+    await waitForHydration(page)
+    await expect(page.getByTestId('cjs-builtin-interop')).toHaveText(
+      'cjs-builtin-interop: ok',
+    )
+  })
+
   test('use cache function', async ({ page }) => {
     await page.goto(f.url())
     await waitForHydration(page)

packages/plugin-rsc/examples/basic/package.json

@@ -21,6 +21,7 @@
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "latest",
     "@vitejs/plugin-rsc": "latest",
+    "@vitejs/test-dep-cjs-events-extend": "file:./test-dep/cjs-events-extend",
     "@vitejs/test-dep-client-in-server": "file:./test-dep/client-in-server",
     "@vitejs/test-dep-client-in-server2": "file:./test-dep/client-in-server2",
     "@vitejs/test-dep-css-in-server": "file:./test-dep/css-in-server",

packages/plugin-rsc/examples/basic/src/routes/deps/cjs-builtin-interop/server.tsx

@@ -0,0 +1,10 @@
+// @ts-ignore
+import * as testDep from '@vitejs/test-dep-cjs-events-extend'
+
+export function TestCjsBuiltinInterop() {
+  return (
+    <div data-testid="cjs-builtin-interop">
+      cjs-builtin-interop: {testDep.test}
+    </div>
+  )
+}

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

@@ -23,6 +23,7 @@ import { TestChunk2 } from './chunk2/server'
 import { ClientCounter, Hydrated } from './client'
 import { TestClientError } from './client-error/client'
 import { TestCssQueries } from './css-queries/server'
+import { TestCjsBuiltinInterop } from './deps/cjs-builtin-interop/server'
 import { TestClientInServer } from './deps/client-in-server/server'
 import { TestServerInClient } from './deps/server-in-client/client'
 import { TestServerInServer } from './deps/server-in-server/server'
@@ -123,6 +124,7 @@ export function Root(props: { url: URL }) {
         <TestClientChunkServer />
         <TestChunk2 />
         <TestUseId />
+        <TestCjsBuiltinInterop />
       </body>
     </html>
   )

packages/plugin-rsc/examples/basic/test-dep/cjs-events-extend/index.js

@@ -0,0 +1,10 @@
+const EventEmitter = require('node:events')
+
+class CustomEventEmitter extends EventEmitter {
+  constructor() {
+    super()
+    this.testValue = 'ok'
+  }
+}
+
+module.exports.test = new CustomEventEmitter().testValue || 'ko'

packages/plugin-rsc/examples/basic/test-dep/cjs-events-extend/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "@vitejs/test-dep-cjs-events-extend",
+  "version": "0.0.0",
+  "private": true,
+  "type": "commonjs",
+  "exports": "./index.js",
+  "peerDependencies": {
+    "react": "*"
+  }
+}

packages/plugin-rsc/package.json

@@ -58,6 +58,7 @@
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "workspace:*",
     "@vitejs/test-dep-cjs-and-esm": "./test-dep/cjs-and-esm",
+    "@vitejs/test-dep-cjs-falsy-primitive": "./test-dep/cjs-falsy-primitive",
     "picocolors": "^1.1.1",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",

packages/plugin-rsc/src/transforms/cjs.test.ts

@@ -44,7 +44,7 @@ if (true) {
     expect(await testTransform(input)).toMatchInlineSnapshot(`
       "let __filename = "/test.js"; let __dirname = "/";
       let exports = {}; const module = { exports };
-      function __cjs_interop__(m) { return m.__cjs_module_runner_transform ? m.default : m; }
+      function __cjs_interop__(m) {return m.__cjs_module_runner_transform || "default" in m && Object.keys(m).every((k) => k === "default" || m[k] === m.default[k]) ? m.default : m;}
       if (true) {
         module.exports = (__cjs_interop__(await import('./cjs/use-sync-external-store.production.js')));
       } else {
@@ -69,7 +69,7 @@ if (true) {
     expect(await testTransform(input)).toMatchInlineSnapshot(`
       "let __filename = "/test.js"; let __dirname = "/";
       let exports = {}; const module = { exports };
-      function __cjs_interop__(m) { return m.__cjs_module_runner_transform ? m.default : m; }
+      function __cjs_interop__(m) {return m.__cjs_module_runner_transform || "default" in m && Object.keys(m).every((k) => k === "default" || m[k] === m.default[k]) ? m.default : m;}
       const __cjs_to_esm_hoist_0 = __cjs_interop__(await import("react"));
       const __cjs_to_esm_hoist_1 = __cjs_interop__(await import("react-dom"));
       "production" !== process.env.NODE_ENV && (function() { 
@@ -100,7 +100,7 @@ function test() {
     expect(await testTransform(input)).toMatchInlineSnapshot(`
       "let __filename = "/test.js"; let __dirname = "/";
       let exports = {}; const module = { exports };
-      function __cjs_interop__(m) { return m.__cjs_module_runner_transform ? m.default : m; }
+      function __cjs_interop__(m) {return m.__cjs_module_runner_transform || "default" in m && Object.keys(m).every((k) => k === "default" || m[k] === m.default[k]) ? m.default : m;}
       const __cjs_to_esm_hoist_0 = __cjs_interop__(await import("te" + "st"));
       const __cjs_to_esm_hoist_1 = __cjs_interop__(await import("test"));
       const __cjs_to_esm_hoist_2 = __cjs_interop__(await import("test"));
@@ -196,6 +196,12 @@ function test() {
         },
         "depPrimitive": "[ok]",
         "dualLib": "ok",
+        "testExternalFalsyPrimitive": {
+          "ok": true,
+        },
+        "testNodeBuiltins": {
+          "nodeEventsOk": true,
+        },
       }
     `)
   })

packages/plugin-rsc/src/transforms/cjs.ts

@@ -9,9 +9,23 @@ import { analyze } from 'periscopic'
 // replacing require("xxx") into import("xxx") affects Vite's resolution.
 
 // Runtime helper to handle CJS/ESM interop when transforming require() to import()
-// Only unwrap .default for modules that were transformed by this plugin (marked with __cjs_module_runner_transform)
+// Unwrap .default for modules
+// 1. if it was transformed by this plugin (marked with __cjs_module_runner_transform)
+// 2. if all named exports point to .default properties (common CJS pattern)
+//    this is particularly important for Node built-in modules consumptions;
+//    where the built-in modules are not transformed by this plugin but still follow the CJS export pattern
+//    see [getESMFacade](https://github.com/nodejs/node/blob/f200685d9930404d610a52d9e06513bf0a821ed4/lib/internal/bootstrap/realm.js#L347-L360)
+//
 // This ensures we don't incorrectly unwrap .default on genuine ESM modules
-const CJS_INTEROP_HELPER = `function __cjs_interop__(m) { return m.__cjs_module_runner_transform ? m.default : m; }`
+function __cjs_interop__(m: any) {
+  return m.__cjs_module_runner_transform ||
+    ('default' in m &&
+      Object.keys(m).every((k) => k === 'default' || m[k] === m.default[k]))
+    ? m.default
+    : m
+}
+
+const CJS_INTEROP_HELPER = __cjs_interop__.toString().replace(/\n\s*/g, '')
 
 export function transformCjsToEsm(
   code: string,

packages/plugin-rsc/src/transforms/fixtures/cjs/entry.mjs

@@ -2,10 +2,13 @@ import depDefault from './dep1.cjs'
 import * as depNamespace from './dep2.cjs'
 import dualLib from './dual-lib.cjs'
 import depExports from './exports.cjs'
+import testExternalFalsyPrimitive from './external-falsy-primitive.cjs'
 import depFnRequire from './function-require.cjs'
 import depFn from './function.cjs'
 import cjsGlobals from './globals.cjs'
+import testNodeBuiltins from './node-builtins.cjs'
 import depPrimitive from './primitive.cjs'
+
 export {
   depDefault,
   depNamespace,
@@ -15,4 +18,6 @@ export {
   depFnRequire,
   dualLib,
   cjsGlobals,
+  testNodeBuiltins,
+  testExternalFalsyPrimitive,
 }

packages/plugin-rsc/src/transforms/fixtures/cjs/external-falsy-primitive.cjs

@@ -0,0 +1,3 @@
+const lib = require('@vitejs/test-dep-cjs-falsy-primitive')
+
+exports.ok = lib === false

packages/plugin-rsc/src/transforms/fixtures/cjs/node-builtins.cjs

@@ -0,0 +1,10 @@
+const EventEmitter = require('node:events')
+
+class CustomEmitter extends EventEmitter {
+  constructor() {
+    super()
+    this.custom = true
+  }
+}
+
+exports.nodeEventsOk = new CustomEmitter().custom

packages/plugin-rsc/test-dep/cjs-falsy-primitive/index.cjs

@@ -0,0 +1 @@
+module.exports = false

packages/plugin-rsc/test-dep/cjs-falsy-primitive/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "@vitejs/test-dep-cjs-falsy-primitive",
+  "private": true,
+  "main": "./index.cjs"
+}