ESM implementation of module preinitialization

fixtures/flight-esm/.nvmrc

@@ -0,0 +1 @@
+v18

fixtures/flight-esm/server/global.js

@@ -10,6 +10,7 @@ const compress = require('compression');
 const chalk = require('chalk');
 const express = require('express');
 const http = require('http');
+const React = require('react');
 
 const {renderToPipeableStream} = require('react-dom/server');
 const {createFromNodeStream} = require('react-server-dom-esm/client');
@@ -62,23 +63,39 @@ app.all('/', async function (req, res, next) {
   if (req.accepts('text/html')) {
     try {
       const rscResponse = await promiseForData;
-
       const moduleBaseURL = '/src';
 
       // For HTML, we're a "client" emulator that runs the client code,
       // so we start by consuming the RSC payload. This needs the local file path
       // to load the source files from as well as the URL path for preloads.
-      const root = await createFromNodeStream(
-        rscResponse,
-        moduleBasePath,
-        moduleBaseURL
-      );
+
+      let root;
+      let Root = () => {
+        if (root) {
+          return React.use(root);
+        }
+
+        return React.use(
+          (root = createFromNodeStream(
+            rscResponse,
+            moduleBasePath,
+            moduleBaseURL
+          ))
+        );
+      };
       // Render it into HTML by resolving the client components
       res.set('Content-type', 'text/html');
-      const {pipe} = renderToPipeableStream(root, {
-        // TODO: bootstrapModules inserts a preload before the importmap which causes
-        // the import map to be invalid. We need to fix that in Float somehow.
-        // bootstrapModules: ['/src/index.js'],
+      const {pipe} = renderToPipeableStream(React.createElement(Root), {
+        importMap: {
+          imports: {
+            react: 'https://esm.sh/react@experimental?pin=v124&dev',
+            'react-dom': 'https://esm.sh/react-dom@experimental?pin=v124&dev',
+            'react-dom/': 'https://esm.sh/react-dom@experimental&pin=v124&dev/',
+            'react-server-dom-esm/client':
+              '/node_modules/react-server-dom-esm/esm/react-server-dom-esm-client.browser.development.js',
+          },
+        },
+        bootstrapModules: ['/src/index.js'],
       });
       pipe(res);
     } catch (e) {
@@ -89,6 +106,7 @@ app.all('/', async function (req, res, next) {
   } else {
     try {
       const rscResponse = await promiseForData;
+
       // For other request, we pass-through the RSC payload.
       res.set('Content-type', 'text/x-component');
       rscResponse.on('data', data => {

fixtures/flight-esm/src/App.js

@@ -9,16 +9,6 @@ import {getServerState} from './ServerState.js';
 
 const h = React.createElement;
 
-const importMap = {
-  imports: {
-    react: 'https://esm.sh/react@experimental?pin=v124&dev',
-    'react-dom': 'https://esm.sh/react-dom@experimental?pin=v124&dev',
-    'react-dom/': 'https://esm.sh/react-dom@experimental&pin=v124&dev/',
-    'react-server-dom-esm/client':
-      '/node_modules/react-server-dom-esm/esm/react-server-dom-esm-client.browser.development.js',
-  },
-};
-
 export default async function App() {
   const res = await fetch('http://localhost:3001/todos');
   const todos = await res.json();
@@ -42,12 +32,6 @@ export default async function App() {
         rel: 'stylesheet',
         href: '/src/style.css',
         precedence: 'default',
-      }),
-      h('script', {
-        type: 'importmap',
-        dangerouslySetInnerHTML: {
-          __html: JSON.stringify(importMap),
-        },
       })
     ),
     h(
@@ -84,9 +68,7 @@ export default async function App() {
             'Like'
           )
         )
-      ),
-      // TODO: Move this to bootstrapModules.
-      h('script', {type: 'module', src: '/src/index.js'})
+      )
     )
   );
 }

fixtures/flight/server/global.js

@@ -147,7 +147,7 @@ app.all('/', async function (req, res, next) {
       let root;
       let Root = () => {
         if (root) {
-          return root;
+          return React.use(root);
         }
         return React.use(
           (root = createFromNodeStream(

fixtures/flight/server/region.js

@@ -95,6 +95,9 @@ async function renderApp(res, returnValue) {
   // For client-invoked server actions we refresh the tree and return a return value.
   const payload = returnValue ? {returnValue, root} : root;
   const {pipe} = renderToPipeableStream(payload, moduleMap);
+  await new Promise(res => {
+    setTimeout(res, 1000);
+  });
   pipe(res);
 }
 

packages/react-client/src/forks/ReactFlightClientConfig.dom-browser-esm.js

@@ -8,6 +8,7 @@
  */
 
 export * from 'react-client/src/ReactFlightClientConfigBrowser';
-export * from 'react-server-dom-esm/src/ReactFlightClientConfigESMBundler';
+export * from 'react-server-dom-esm/src/ReactFlightClientConfigBundlerESM';
+export * from 'react-server-dom-esm/src/ReactFlightClientConfigTargetESMBrowser';
 export * from 'react-dom-bindings/src/shared/ReactFlightClientConfigDOM';
 export const usedWithSSR = false;

packages/react-client/src/forks/ReactFlightClientConfig.dom-node-esm.js

@@ -7,7 +7,8 @@
  * @flow
  */
 
-export * from 'react-client/src/ReactFlightClientConfigBrowser';
-export * from 'react-server-dom-esm/src/ReactFlightClientConfigESMBundler';
+export * from 'react-client/src/ReactFlightClientConfigNode';
+export * from 'react-server-dom-esm/src/ReactFlightClientConfigBundlerESM';
+export * from 'react-server-dom-esm/src/ReactFlightClientConfigTargetESMServer';
 export * from 'react-dom-bindings/src/shared/ReactFlightClientConfigDOM';
 export const usedWithSSR = true;

packages/react-dom-bindings/src/shared/ReactFlightClientConfigDOM.js

@@ -64,7 +64,18 @@ export function dispatchHint(code: string, model: HintModel): void {
   }
 }
 
-export function preinitModulesForSSR(href: string, crossOrigin: ?string) {
+export function preinitModuleForSSR(href: string, crossOrigin: ?string) {
+  const dispatcher = ReactDOMCurrentDispatcher.current;
+  if (dispatcher) {
+    if (typeof crossOrigin === 'string') {
+      dispatcher.preinitModule(href, {crossOrigin});
+    } else {
+      dispatcher.preinitModule(href);
+    }
+  }
+}
+
+export function preinitScriptForSSR(href: string, crossOrigin: ?string) {
   const dispatcher = ReactDOMCurrentDispatcher.current;
   if (dispatcher) {
     if (typeof crossOrigin === 'string') {

packages/react-server-dom-esm/src/ReactFlightClientConfigESMBundler.js → packages/react-server-dom-esm/src/ReactFlightClientConfigBundlerESM.js

@@ -12,13 +12,16 @@ import type {
   FulfilledThenable,
   RejectedThenable,
 } from 'shared/ReactTypes';
+import type {ModuleLoading} from 'react-client/src/ReactFlightClientConfig';
 
-export type SSRManifest = string; // Module root path
+export type SSRModuleMap = string; // Module root path
 
 export type ServerManifest = string; // Module root path
 
 export type ServerReferenceId = string;
 
+import {prepareDestinationForModuleImpl} from 'react-client/src/ReactFlightClientConfig';
+
 export opaque type ClientReferenceMetadata = [
   string, // module path
   string, // export name
@@ -30,8 +33,21 @@ export opaque type ClientReference<T> = {
   name: string,
 };
 
+// The reason this function needs to defined here in this file instead of just
+// being exported directly from the WebpackDestination... file is because the
+// ClientReferenceMetadata is opaque and we can't unwrap it there.
+// This should get inlined and we could also just implement an unwrapping function
+// though that risks it getting used in places it shouldn't be. This is unfortunate
+// but currently it seems to be the best option we have.
+export function prepareDestinationForModule(
+  moduleLoading: ModuleLoading,
+  metadata: ClientReferenceMetadata,
+) {
+  prepareDestinationForModuleImpl(moduleLoading, metadata[0]);
+}
+
 export function resolveClientReference<T>(
-  bundlerConfig: SSRManifest,
+  bundlerConfig: SSRModuleMap,
   metadata: ClientReferenceMetadata,
 ): ClientReference<T> {
   const baseURL = bundlerConfig;

packages/react-server-dom-esm/src/ReactFlightClientConfigTargetESMBrowser.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+export type ModuleLoading = null;
+
+export function prepareDestinationForModuleImpl(
+  moduleLoading: ModuleLoading,
+  chunks: mixed,
+) {
+  // In the browser we don't need to prepare our destination since the browser is the Destination
+}

packages/react-server-dom-esm/src/ReactFlightClientConfigTargetESMServer.js

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import {preinitModuleForSSR} from 'react-client/src/ReactFlightClientConfig';
+
+export type ModuleLoading =
+  | null
+  | string
+  | {
+      prefix: string,
+      crossOrigin?: string,
+    };
+
+export function prepareDestinationForModuleImpl(
+  moduleLoading: ModuleLoading,
+  // Chunks are double-indexed [..., idx, filenamex, idy, filenamey, ...]
+  mod: string,
+) {
+  if (typeof moduleLoading === 'string') {
+    preinitModuleForSSR(moduleLoading + mod, undefined);
+  } else if (moduleLoading !== null) {
+    preinitModuleForSSR(moduleLoading.prefix + mod, moduleLoading.crossOrigin);
+  }
+}

packages/react-server-dom-esm/src/ReactFlightDOMClientBrowser.js

@@ -36,6 +36,7 @@ export type Options = {
 function createResponseFromOptions(options: void | Options) {
   return createResponse(
     options && options.moduleBaseURL ? options.moduleBaseURL : '',
+    null,
     options && options.callServer ? options.callServer : undefined,
   );
 }

packages/react-server-dom-esm/src/ReactFlightDOMClientNode.js

@@ -41,9 +41,13 @@ export function createServerReference<A: Iterable<any>, T>(
 function createFromNodeStream<T>(
   stream: Readable,
   moduleRootPath: string,
-  moduleBaseURL: string, // TODO: Used for preloading hints
+  moduleBaseURL: string,
 ): Thenable<T> {
-  const response: Response = createResponse(moduleRootPath, noServerCall);
+  const response: Response = createResponse(
+    moduleRootPath,
+    moduleBaseURL,
+    noServerCall,
+  );
   stream.on('data', chunk => {
     processBinaryChunk(response, chunk);
   });

packages/react-server-dom-webpack/src/ReactFlightClientConfigTargetWebpackServer.js

@@ -7,7 +7,7 @@
  * @flow
  */
 
-import {preinitModulesForSSR} from 'react-client/src/ReactFlightClientConfig';
+import {preinitScriptForSSR} from 'react-client/src/ReactFlightClientConfig';
 
 export type ModuleLoading = null | {
   prefix: string,
@@ -21,7 +21,7 @@ export function prepareDestinationWithChunks(
 ) {
   if (moduleLoading !== null) {
     for (let i = 1; i < chunks.length; i += 2) {
-      preinitModulesForSSR(
+      preinitScriptForSSR(
         moduleLoading.prefix + chunks[i],
         moduleLoading.crossOrigin,
       );

scripts/shared/inlinedHostConfigs.js

@@ -112,6 +112,7 @@ module.exports = [
       'react-server-dom-esm',
       'react-server-dom-esm/client',
       'react-server-dom-esm/client.browser',
+      'react-server-dom-esm/src/ReactFlightDOMClientBrowser.js', // react-server-dom-esm/client.browser
       'react-devtools',
       'react-devtools-core',
       'react-devtools-shell',
@@ -214,7 +215,8 @@ module.exports = [
       'react-server-dom-esm/client.node',
       'react-server-dom-esm/server',
       'react-server-dom-esm/server.node',
-      'react-server-dom-esm/src/ReactFlightDOMServerNode.js', // react-server-dom-webpack/server.node
+      'react-server-dom-esm/src/ReactFlightDOMServerNode.js', // react-server-dom-esm/server.node
+      'react-server-dom-esm/src/ReactFlightDOMClientNode.js', // react-server-dom-esm/client.node
       'react-devtools',
       'react-devtools-core',
       'react-devtools-shell',