initialize hook PoC

lib/internal/modules/esm/hooks.js

@@ -124,7 +124,11 @@ class Hooks {
    * @param {string} urlOrSpecifier
    * @param {string} parentURL
    */
-  async register(urlOrSpecifier, parentURL) {
+  async register(urlOrSpecifier, options) {
+    const {
+      parentURL = 'data:',
+      data,
+    } = options;
     const moduleLoader = require('internal/process/esm_loader').esmLoader;
 
     const keyedExports = await moduleLoader.import(
@@ -133,7 +137,7 @@ class Hooks {
       kEmptyObject,
     );
 
-    this.addCustomLoader(urlOrSpecifier, keyedExports);
+    this.addCustomLoader(urlOrSpecifier, keyedExports, data);
   }
 
   /**
@@ -142,13 +146,17 @@ class Hooks {
    * @param {string} url Custom loader specifier
    * @param {Record<string, unknown>} exports
    */
-  addCustomLoader(url, exports) {
+  addCustomLoader(url, exports, data) {
     const {
+      initialize,
       globalPreload,
       resolve,
       load,
     } = pluckHooks(exports);
 
+    if (initialize) {
+      initialize(data);
+    }
     if (globalPreload) {
       ArrayPrototypePush(this.#chains.globalPreload, { fn: globalPreload, url });
     }
@@ -577,12 +585,12 @@ class HooksProxy {
     return body;
   }
 
-  makeSyncRequest(method, ...args) {
+  makeSyncRequest(method, args, transferList) {
     this.#waitForWorker();
 
     // Pass work to the worker.
     debug('post sync message to worker', { method, args });
-    this.#worker.postMessage({ method, args });
+    this.#worker.postMessage({ method, args }, transferList);
 
     let response;
     do {
@@ -660,12 +668,16 @@ ObjectSetPrototypeOf(HooksProxy.prototype, null);
  * @returns {ExportedHooks}
  */
 function pluckHooks({
+  initialize,
   globalPreload,
   resolve,
   load,
 }) {
   const acceptedHooks = { __proto__: null };
 
+  if (initialize) {
+    acceptedHooks.initialize = initialize;
+  }
   if (globalPreload) {
     acceptedHooks.globalPreload = globalPreload;
   }

lib/internal/modules/esm/loader.js

@@ -299,8 +299,8 @@ class CustomizedModuleLoader extends DefaultModuleLoader {
    *                           registered if using it package name as specifier
    * @returns {{ format: string, url: URL['href'] }}
    */
-  register(originalSpecifier, parentURL) {
-    return hooksProxy.makeSyncRequest('register', originalSpecifier, parentURL);
+  register(originalSpecifier, options) {
+    return hooksProxy.makeSyncRequest('register', [originalSpecifier, options], options.transferList);
   }
 
   /**
@@ -313,7 +313,7 @@ class CustomizedModuleLoader extends DefaultModuleLoader {
    * @returns {{ format: string, url: URL['href'] }}
    */
   resolve(originalSpecifier, parentURL, importAssertions) {
-    return hooksProxy.makeSyncRequest('resolve', originalSpecifier, parentURL, importAssertions);
+    return hooksProxy.makeSyncRequest('resolve', [originalSpecifier, parentURL, importAssertions]);
   }
 
   async #getModuleJob(specifier, parentURL, importAssertions) {
@@ -404,15 +404,15 @@ function getHooksProxy() {
  * register(new URL('./myLoader.js', import.meta.url));
  * ```
  */
-function register(specifier, parentURL = 'data:') {
+function register(specifier, options = { __proto__: null }) {
   // TODO: Remove this limitation in a follow-up before `register` is released publicly
   if (getOptionValue('--experimental-loader').length < 1) {
     throw new ERR_ESM_LOADER_REGISTRATION_UNAVAILABLE();
   }
 
   const moduleLoader = require('internal/process/esm_loader').esmLoader;
 
-  moduleLoader.register(`${specifier}`, parentURL);
+  moduleLoader.register(`${specifier}`, options);
 }
 
 module.exports = {

poc.loader.mjs

@@ -0,0 +1,4 @@
+export function initialize({ entryPoint, port }) {
+    console.log('initialize loader', { entryPoint });
+    port.postMessage('loader initialized');
+}

poc.mjs

@@ -0,0 +1,16 @@
+import module from 'node:module';
+
+const { port1, port2 } = new MessageChannel();
+
+module.register('./poc.loader.mjs', {
+  parentURL: import.meta.url,
+  data: {
+    entryPoint: process.argv[1],
+    port: port2
+  },
+  transferList: [port2],
+});
+
+port1.once('message', (message) => {
+  console.log(message);
+});

test/es-module/test-esm-loader-programmatically.mjs

@@ -15,7 +15,7 @@ const commonArgs = [
 
 const commonEvals = {
   import: (module) => `await import(${JSON.stringify(module)});`,
-  register: (loader, parentURL = 'file:///') => `register(${JSON.stringify(loader)}, ${JSON.stringify(parentURL)});`,
+  register: (loader, parentURL = 'file:///') => `register(${JSON.stringify(loader)}, { parentURL: ${JSON.stringify(parentURL)} });`,
   dynamicImport: (module) => `await import(${JSON.stringify(`data:text/javascript,${encodeURIComponent(module)}`)});`,
   staticImport: (module) => `import ${JSON.stringify(`data:text/javascript,${encodeURIComponent(module)}`)};`,
 };

test/fixtures/es-module-loaders/register-programmatically-loader-resolve.mjs

@@ -1,3 +1,3 @@
 import { register } from 'node:module';
 
-register('./loader-resolve-passthru.mjs', import.meta.url);
+register('./loader-resolve-passthru.mjs', { parentURL: import.meta.url });