chaining loader hooks

lib/internal/modules/esm/hooks.js

@@ -107,7 +107,7 @@ class Hooks {
   #validatedUrls = new SafeSet();
 
   constructor(userLoaders) {
-    this.#addCustomLoaders(userLoaders);
+    this.addCustomLoaders(userLoaders);
   }
 
   /**
@@ -116,7 +116,7 @@ class Hooks {
    * @param {import('./loader.js).KeyedExports} customLoaders Exports from user-defined loaders
    *  (as returned by `ModuleLoader.import()`).
    */
-  #addCustomLoaders(customLoaders = []) {
+  addCustomLoaders(customLoaders = []) {
     for (let i = 0; i < customLoaders.length; i++) {
       const {
         exports,

lib/internal/modules/esm/loader.js

@@ -142,7 +142,7 @@ class DefaultModuleLoader {
    *                                     point.
    * @param {Record<string, string>} importAssertions Validations for the
    *                                                  module import.
-   * @returns {Promise<ModuleJob>} The (possibly pending) module job
+   * @returns {ModuleJob} The (possibly pending) module job
    */
   getModuleJob(specifier, parentURL, importAssertions) {
     const resolveResult = this.resolve(specifier, parentURL, importAssertions);
@@ -157,7 +157,7 @@ class DefaultModuleLoader {
     }
 
     if (job === undefined) {
-      job = this.#createModuleJob(url, resolvedImportAssertions, parentURL, format);
+      job = this.createModuleJob(url, resolvedImportAssertions, parentURL, format);
     }
 
     return job;
@@ -174,7 +174,7 @@ class DefaultModuleLoader {
    *                          `resolve` hook
    * @returns {Promise<ModuleJob>} The (possibly pending) module job
    */
-  #createModuleJob(url, importAssertions, parentURL, format) {
+  createModuleJob(url, importAssertions, parentURL, format) {
     const moduleProvider = async (url, isMain) => {
       const {
         format: finalFormat,
@@ -392,4 +392,7 @@ function ModuleLoader(useCustomLoadersIfPresent = true) {
 }
 ObjectSetPrototypeOf(ModuleLoader.prototype, null);
 
-exports.ModuleLoader = ModuleLoader;
+module.exports = {
+  DefaultModuleLoader,
+  ModuleLoader,
+};

lib/internal/modules/esm/utils.js

@@ -2,7 +2,7 @@
 
 const {
   ArrayIsArray,
-  ArrayPrototypePushApply,
+  PromisePrototypeThen,
   SafeSet,
   SafeWeakMap,
   ObjectFreeze,
@@ -109,9 +109,45 @@ async function initializeHooks() {
     cwd = '/';
   }
 
-  const { ModuleLoader } = require('internal/modules/esm/loader');
+
+  const { Hooks } = require('internal/modules/esm/hooks');
+  const hooks = new Hooks();
+
+  const { DefaultModuleLoader } = require('internal/modules/esm/loader');
+  class ModuleLoader extends DefaultModuleLoader {
+    async asyncGetModuleJob(specifier, parentURL, importAssertions) {
+      const resolveResult = await hooks.resolve(specifier, parentURL, importAssertions);
+      const { url, format } = resolveResult;
+      const resolvedImportAssertions = resolveResult.importAssertions ?? importAssertions;
+
+      let job = this.moduleMap.get(url, resolvedImportAssertions.type);
+
+      // CommonJS will set functions for lazy job evaluation.
+      if (typeof job === 'function') {
+        this.moduleMap.set(url, undefined, job = job());
+      }
+
+      if (job === undefined) {
+        job = this.createModuleJob(url, resolvedImportAssertions, parentURL, format);
+      }
+
+      return job;
+    }
+    getModuleJob(specifier, parentURL, importAssertions) {
+      const jobPromise = this.asyncGetModuleJob(specifier, parentURL, importAssertions);
+      return {
+        async run() { return (await jobPromise).run(); },
+        get modulePromise() {
+          return PromisePrototypeThen(jobPromise, (job) => job.modulePromise);
+        },
+        get linked() {
+          return PromisePrototypeThen(jobPromise, (job) => job.linked);
+        }
+      };
+    }
+    load(url, context) { return hooks.load(url, context); }
+  }
   const privateModuleLoader = new ModuleLoader(false);
-  const importedCustomLoaders = [];
 
   const parentURL = pathToFileURL(cwd).href;
 
@@ -125,12 +161,9 @@ async function initializeHooks() {
       kEmptyObject,
     );
 
-    ArrayPrototypePushApply(importedCustomLoaders, keyedExportsSublist);
+    hooks.addCustomLoaders(keyedExportsSublist);
   }
 
-  const { Hooks } = require('internal/modules/esm/hooks');
-  const hooks = new Hooks(importedCustomLoaders);
-
   const preloadScripts = hooks.initializeGlobalPreload();
 
   return { __proto__: null, hooks, preloadScripts };

test/fixtures/es-module-loaders/loader-load-passthru.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function load(url, context, next) {
   // This check is needed to make sure that we don't prevent the

test/fixtures/es-module-loaders/loader-load-receiving-modified-context.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function load(url, context, next) {
   writeSync(1, `${context.foo}\n`); // This log is deliberate

test/fixtures/es-module-loaders/loader-log-args.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function resolve(...args) {
   writeSync(1, `resolve arg count: ${args.length}\n`);

test/fixtures/es-module-loaders/loader-resolve-42.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function resolve(specifier, context, next) {
   // This check is needed to make sure that we don't prevent the

test/fixtures/es-module-loaders/loader-resolve-foo.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function resolve(specifier, context, next) {
   // This check is needed to make sure that we don't prevent the

test/fixtures/es-module-loaders/loader-resolve-passthru.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function resolve(specifier, context, next) {
   // This check is needed to make sure that we don't prevent the

test/fixtures/es-module-loaders/loader-resolve-receiving-modified-context.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function resolve(specifier, context, next) {
   writeSync(1, `${context.foo}\n`); // This log is deliberate

test/fixtures/es-module-loaders/loader-resolve-strip-xxx.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function resolve(specifier, context, nextResolve) {
   writeSync(1, `loader-a ${specifier}\n`);

test/fixtures/es-module-loaders/loader-resolve-strip-yyy.mjs

@@ -1,4 +1,4 @@
-import { writeSync } from 'fs';
+import { writeSync } from 'node:fs';
 
 export async function resolve(specifier, context, nextResolve) {
   writeSync(1, `loader-b ${specifier}\n`);