Handle async module for client components (#39953)

### Problem

esm modules imports from client components will be compiled to `m = import('module-name')` when webpack bundles them for server components flight rendering. In this case, they will all become async modules since dyanmic imports will return a promise which react flight cannot handle it then results into module resolving error on server flight rendering.

### Solution

* React flight renderer supports handling async modules in facebook/react#25138
* On next.js side leverage the module proxy change for each client reference, to make sure it always resolve the correct client module

The idea is wrapping each module with a module proxy, and if the module is async and accessed as thenable, it will return a new module reference with `async` label to tell react to handle it as async modules:

exported client reference `*` --> not async module (non thenable) --> original module reference `''`
exported client reference `*` --> it's async module (thenable) --> wrapped module reference `'*'` with `async` label

### Note

Since we need to check if user having incorrect gSSP/gSP specifying in layout client componet, so we still need to parse it and assign those info to the proxy (Does client module containing `ssr`, `ssg` exports). Otherwise the proxy will return the cached module reference

Author: huozhi

package.json

@@ -177,8 +177,8 @@
     "react-17": "npm:react@17.0.2",
     "react-dom": "18.2.0",
     "react-dom-17": "npm:react-dom@17.0.2",
-    "react-dom-exp": "npm:react-dom@0.0.0-experimental-6ef466c68-20220816",
-    "react-exp": "npm:react@0.0.0-experimental-6ef466c68-20220816",
+    "react-dom-exp": "npm:react-dom@0.0.0-experimental-0de3ddf56-20220825",
+    "react-exp": "npm:react@0.0.0-experimental-0de3ddf56-20220825",
     "react-ssr-prepass": "1.0.8",
     "react-virtualized": "9.22.3",
     "relay-compiler": "13.0.2",

packages/next/build/analysis/get-page-static-info.ts

@@ -28,7 +28,7 @@ export interface PageStaticInfo {
  *   - Modules with `export function getStaticProps | getServerSideProps`
  *   - Modules with `export { getStaticProps | getServerSideProps } <from ...>`
  */
-function checkExports(swcAST: any) {
+export function checkExports(swcAST: any): { ssr: boolean; ssg: boolean } {
   if (Array.isArray(swcAST?.body)) {
     try {
       for (const node of swcAST.body) {

packages/next/build/webpack/loaders/next-flight-client-loader.ts

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import { checkExports } from '../../../analysis/get-page-static-info'
+import { parse } from '../../../swc'
+
+export default async function transformSource(
+  this: any,
+  source: string
+): Promise<string> {
+  const { resourcePath } = this
+
+  const transformedSource = source
+  if (typeof transformedSource !== 'string') {
+    throw new Error('Expected source to have been transformed to a string.')
+  }
+
+  const swcAST = await parse(transformedSource, {
+    filename: resourcePath,
+    isModule: 'unknown',
+  })
+  const { ssg, ssr } = checkExports(swcAST)
+
+  const output = `
+const { createProxy } = require("next/dist/build/webpack/loaders/next-flight-client-loader/module-proxy")\n
+module.exports = createProxy(${JSON.stringify(
+    resourcePath
+  )}, { ssr: ${ssr}, ssg: ${ssg} })
+`
+  return output
+}

packages/next/build/webpack/loaders/next-flight-client-loader/index.ts

@@ -0,0 +1,119 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// Modified from https://github.com/facebook/react/blob/main/packages/react-server-dom-webpack/src/ReactFlightWebpackNodeRegister.js
+
+const MODULE_REFERENCE = Symbol.for('react.module.reference')
+const PROMISE_PROTOTYPE = Promise.prototype
+
+const proxyHandlers: ProxyHandler<object> = {
+  get: function (target: any, name: string, _receiver: any) {
+    switch (name) {
+      // These names are read by the Flight runtime if you end up using the exports object.
+      case '$$typeof':
+        // These names are a little too common. We should probably have a way to
+        // have the Flight runtime extract the inner target instead.
+        return target.$$typeof
+      case 'filepath':
+        return target.filepath
+      case 'name':
+        return target.name
+      case 'async':
+        return target.async
+      // We need to special case this because createElement reads it if we pass this
+      // reference.
+      case 'defaultProps':
+        return undefined
+      case '__esModule':
+        // Something is conditionally checking which export to use. We'll pretend to be
+        // an ESM compat module but then we'll check again on the client.
+        target.default = {
+          $$typeof: MODULE_REFERENCE,
+          filepath: target.filepath,
+          // This a placeholder value that tells the client to conditionally use the
+          // whole object or just the default export.
+          name: '',
+          async: target.async,
+
+          ssr: target.ssr,
+          ssg: target.ssg,
+        }
+        return true
+      case 'then':
+        if (!target.async) {
+          // If this module is expected to return a Promise (such as an AsyncModule) then
+          // we should resolve that with a client reference that unwraps the Promise on
+          // the client.
+          const then = function then(
+            resolve: (res: any) => void,
+            _reject: (err: any) => void
+          ) {
+            const moduleReference: Record<string, any> = {
+              $$typeof: MODULE_REFERENCE,
+              filepath: target.filepath,
+              name: '*', // Represents the whole object instead of a particular import.
+              async: true,
+
+              ssr: target.ssr,
+              ssg: target.ssg,
+            }
+            return Promise.resolve(
+              resolve(new Proxy(moduleReference, proxyHandlers))
+            )
+          }
+          // If this is not used as a Promise but is treated as a reference to a `.then`
+          // export then we should treat it as a reference to that name.
+          then.$$typeof = MODULE_REFERENCE
+          then.filepath = target.filepath
+          // then.name is conveniently already "then" which is the export name we need.
+          // This will break if it's minified though.
+          return then
+        }
+        break
+
+      case 'ssg':
+        return target.ssg
+      case 'ssr':
+        return target.ssr
+      default:
+        break
+    }
+    let cachedReference = target[name]
+    if (!cachedReference) {
+      cachedReference = target[name] = {
+        $$typeof: MODULE_REFERENCE,
+        filepath: target.filepath,
+        name: name,
+        async: target.async,
+      }
+    }
+    return cachedReference
+  },
+  getPrototypeOf(_target: object) {
+    // Pretend to be a Promise in case anyone asks.
+    return PROMISE_PROTOTYPE
+  },
+  set: function () {
+    throw new Error('Cannot assign to a client module from a server module.')
+  },
+}
+
+export function createProxy(
+  moduleId: string,
+  { ssr, ssg }: { ssr: boolean; ssg: boolean }
+) {
+  const moduleReference = {
+    $$typeof: MODULE_REFERENCE,
+    filepath: moduleId,
+    name: '*', // Represents the whole object instead of a particular import.
+    async: false,
+
+    ssr,
+    ssg,
+  }
+  return new Proxy(moduleReference, proxyHandlers)
+}