From 3743406b0a44e13de491c8590386a964dbe327bb Mon Sep 17 00:00:00 2001
From: Jacob <3012099+JakobJingleheimer@users.noreply.github.com>
Date: Wed, 25 Aug 2021 22:55:14 +0200
Subject: [PATCH] esm: consolidate ESM loader hooks

doc: update ESM hook examples

esm: fix unsafe primordial

doc: fix ESM example linting

esm: allow source of type ArrayBuffer

doc: update ESM hook changelog to include resolve format

esm: allow all ArrayBuffers and TypedArrays for load hook source

doc: tidy code & API docs

doc: convert ESM source table header from Title Case to Sentence case

doc: add detailed explanation for getPackageType

esm: add caveat that ESMLoader::import() must NOT be renamed

esm: tidy code declaration of getFormat protocolHandlers

doc: correct ESM doc link (bad conflict resolution)

doc: update ESM hook limitation for CJS

esm: tweak preload description

doc: update ESM getPackageType() example explanation

PR-URL: https://github.com/nodejs/node/pull/37468
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Geoffrey Booth <webmaster@geoffreybooth.com>
---
 doc/api/esm.md                                | 312 +++++-----
 lib/internal/modules/cjs/loader.js            |  10 +-
 lib/internal/modules/esm/get_format.js        |  36 +-
 lib/internal/modules/esm/get_source.js        |   2 +-
 lib/internal/modules/esm/load.js              |  32 +
 lib/internal/modules/esm/loader.js            | 553 ++++++++++++------
 lib/internal/modules/esm/module_job.js        |  10 +-
 lib/internal/modules/esm/resolve.js           |   2 +-
 lib/internal/modules/esm/transform_source.js  |   7 -
 lib/internal/modules/esm/translators.js       |  51 +-
 lib/internal/modules/run_main.js              |  10 +-
 lib/internal/process/esm_loader.js            |  52 +-
 lib/internal/process/execution.js             |   2 +-
 lib/repl.js                                   |   4 +-
 test/es-module/test-esm-data-urls.js          |   2 +-
 ...-loader.js => test-esm-example-loader.mjs} |   0
 test/es-module/test-esm-get-source-loader.mjs |   6 -
 test/es-module/test-esm-loader-get-format.mjs |  12 -
 test/es-module/test-esm-loader-modulemap.js   |   4 +-
 .../test-esm-loader-stringify-text.mjs        |  40 ++
 test/es-module/test-esm-loader.mjs            |  83 +++
 test/es-module/test-esm-resolve-hook.mjs      |   8 -
 .../test-esm-transform-source-loader.mjs      |   6 -
 .../builtin-named-exports-loader.mjs          |  18 +-
 .../fixtures/es-module-loaders/get-source.mjs |  10 -
 .../es-module-loaders/hooks-custom.mjs        |  69 +++
 .../es-module-loaders/hooks-obsolete.mjs      |  22 +
 test/fixtures/es-module-loaders/js-loader.mjs |   9 -
 .../loader-invalid-format.mjs                 |   7 +-
 .../loader-unknown-builtin-module.mjs         |  20 +-
 .../es-module-loaders/string-sources.mjs      |  30 +-
 .../es-module-loaders/transform-source.mjs    |  14 -
 test/fixtures/es-modules/file.ext             |   3 +
 test/fixtures/es-modules/file.unknown         |   0
 test/fixtures/es-modules/stateful.mjs         |   5 +
 test/message/esm_display_syntax_error.out     |   3 +-
 .../esm_display_syntax_error_import.out       |   5 +-
 ...esm_display_syntax_error_import_module.out |   5 +-
 .../esm_display_syntax_error_module.out       |   3 +-
 test/message/esm_loader_not_found.out         |  12 +-
 .../esm_loader_not_found_cjs_hint_bare.out    |   6 +-
 ...esm_loader_not_found_cjs_hint_relative.out |  12 +-
 test/message/esm_loader_syntax_error.out      |   3 +-
 .../test-esm-loader-obsolete-hooks.mjs        |   4 +
 .../test-esm-loader-obsolete-hooks.out        |  10 +
 test/parallel/test-bootstrap-modules.js       |   2 +-
 46 files changed, 971 insertions(+), 545 deletions(-)
 create mode 100644 lib/internal/modules/esm/load.js
 delete mode 100644 lib/internal/modules/esm/transform_source.js
 rename test/es-module/{test-esm-example-loader.js => test-esm-example-loader.mjs} (100%)
 delete mode 100644 test/es-module/test-esm-get-source-loader.mjs
 delete mode 100644 test/es-module/test-esm-loader-get-format.mjs
 create mode 100644 test/es-module/test-esm-loader.mjs
 delete mode 100644 test/es-module/test-esm-resolve-hook.mjs
 delete mode 100644 test/es-module/test-esm-transform-source-loader.mjs
 delete mode 100644 test/fixtures/es-module-loaders/get-source.mjs
 create mode 100644 test/fixtures/es-module-loaders/hooks-custom.mjs
 create mode 100644 test/fixtures/es-module-loaders/hooks-obsolete.mjs
 delete mode 100644 test/fixtures/es-module-loaders/js-loader.mjs
 delete mode 100644 test/fixtures/es-module-loaders/transform-source.mjs
 create mode 100644 test/fixtures/es-modules/file.ext
 create mode 100644 test/fixtures/es-modules/file.unknown
 create mode 100644 test/fixtures/es-modules/stateful.mjs
 create mode 100644 test/message/test-esm-loader-obsolete-hooks.mjs
 create mode 100644 test/message/test-esm-loader-obsolete-hooks.out

diff --git a/doc/api/esm.md b/doc/api/esm.md
index fd68e2649baf8e..06eae239c3abcd 100644
--- a/doc/api/esm.md
+++ b/doc/api/esm.md
@@ -7,6 +7,14 @@
 <!-- YAML
 added: v8.5.0
 changes:
+  - version:
+    - REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/37468
+    description:
+      Consolidate loader hooks, removed `getFormat`, `getSource`,
+      `transformSource`, and `getGlobalPreloadCode` hooks
+      added `load` and `globalPreload` hooks
+      allowed returning `format` from either `resolve` or `load` hooks.
   - version:
     - v15.3.0
     - v12.22.0
@@ -604,20 +612,29 @@ CommonJS modules loaded.
 * `specifier` {string}
 * `context` {Object}
   * `conditions` {string[]}
-  * `parentURL` {string}
-* `defaultResolve` {Function}
+  * `parentURL` {string|undefined}
+* `defaultResolve` {Function} The Node.js default resolver.
 * Returns: {Object}
-  * `url` {string}
+  * `format` {string|null|undefined}
+  `'builtin' | 'commonjs' | 'json' | 'module' | 'wasm'`
+  * `url` {string} The absolute url to the import target (such as `file://…`)
 
 The `resolve` hook returns the resolved file URL for a given module specifier
-and parent URL. The module specifier is the string in an `import` statement or
+and parent URL, and optionally its format (such as `'module'`) as a hint to the
+`load` hook. If a format is specified, the `load` hook is ultimately responsible
+for providing the final `format` value (and it is free to ignore the hint
+provided by `resolve`); if `resolve` provides a `format`, a custom `load`
+hook is required even if only to pass the value to the Node.js default `load`
+hook.
+
+The module specifier is the string in an `import` statement or
 `import()` expression, and the parent URL is the URL of the module that imported
 this one, or `undefined` if this is the main entry point for the application.
 
-The `conditions` property on the `context` is an array of conditions for
-[Conditional exports][] that apply to this resolution request. They can be used
-for looking up conditional mappings elsewhere or to modify the list when calling
-the default resolution logic.
+The `conditions` property in `context` is an array of conditions for
+[package exports conditions][Conditional Exports] that apply to this resolution
+request. They can be used for looking up conditional mappings elsewhere or to
+modify the list when calling the default resolution logic.
 
 The current [package exports conditions][Conditional Exports] are always in
 the `context.conditions` array passed into the hook. To guarantee _default
@@ -659,23 +676,29 @@ export async function resolve(specifier, context, defaultResolve) {
 }
 ```
 
-#### `getFormat(url, context, defaultGetFormat)`
+#### `load(url, context, defaultLoad)`
 
 > Note: The loaders API is being redesigned. This hook may disappear or its
 > signature may change. Do not rely on the API described below.
 
+> Note: In a previous version of this API, this was split across 3 separate, now
+> deprecated, hooks (`getFormat`, `getSource`, and `transformSource`).
+
 * `url` {string}
 * `context` {Object}
-* `defaultGetFormat` {Function}
+  * `format` {string|null|undefined} The format optionally supplied by the
+  `resolve` hook.
+* `defaultLoad` {Function}
 * Returns: {Object}
   * `format` {string}
+  * `source` {string|ArrayBuffer|TypedArray}
 
-The `getFormat` hook provides a way to define a custom method of determining how
-a URL should be interpreted. The `format` returned also affects what the
-acceptable forms of source values are for a module when parsing. This can be one
-of the following:
+The `load` hook provides a way to define a custom method of determining how
+a URL should be interpreted, retrieved, and parsed.
 
-| `format`     | Description                    | Acceptable Types For `source` Returned by `getSource` or `transformSource` |
+The final value of `format` must be one of the following:
+
+| `format`     | Description                    | Acceptable types For `source` returned by `resolve` or `load` |
 | ------------ | ------------------------------ | -------------------------------------------------------------------------- |
 | `'builtin'`  | Load a Node.js builtin module  | Not applicable                                                             |
 | `'commonjs'` | Load a Node.js CommonJS module | Not applicable                                                             |
@@ -683,126 +706,78 @@ of the following:
 | `'module'`   | Load an ES module              | { [`string`][], [`ArrayBuffer`][], [`TypedArray`][] }                      |
 | `'wasm'`     | Load a WebAssembly module      | { [`ArrayBuffer`][], [`TypedArray`][] }                                    |
 
-Note: These types all correspond to classes defined in ECMAScript.
-
-* The specific [`ArrayBuffer`][] object is a [`SharedArrayBuffer`][].
-* The specific [`TypedArray`][] object is a [`Uint8Array`][].
-
-Note: If the source value of a text-based format (i.e., `'json'`, `'module'`) is
-not a string, it is converted to a string using [`util.TextDecoder`][].
+The value of `source` is ignored for type `'builtin'` because currently it is
+not possible to replace the value of a Node.js builtin (core) module. The value
+of `source` is ignored for type `'commonjs'` because the CommonJS module loader
+does not provide a mechanism for the ES module loader to override the
+[CommonJS module return value](#commonjs-namespaces). This limitation might be
+overcome in the future.
 
-```js
-/**
- * @param {string} url
- * @param {Object} context (currently empty)
- * @param {Function} defaultGetFormat
- * @returns {Promise<{ format: string }>}
- */
-export async function getFormat(url, context, defaultGetFormat) {
-  if (Math.random() > 0.5) { // Some condition.
-    // For some or all URLs, do some custom logic for determining format.
-    // Always return an object of the form {format: <string>}, where the
-    // format is one of the strings in the preceding table.
-    return {
-      format: 'module',
-    };
-  }
-  // Defer to Node.js for all other URLs.
-  return defaultGetFormat(url, context, defaultGetFormat);
-}
-```
+> **Caveat**: The ESM `load` hook and namespaced exports from CommonJS modules
+> are incompatible. Attempting to use them together will result in an empty
+> object from the import. This may be addressed in the future.
 
-#### `getSource(url, context, defaultGetSource)`
+> Note: These types all correspond to classes defined in ECMAScript.
 
-> Note: The loaders API is being redesigned. This hook may disappear or its
-> signature may change. Do not rely on the API described below.
+* The specific [`ArrayBuffer`][] object is a [`SharedArrayBuffer`][].
+* The specific [`TypedArray`][] object is a [`Uint8Array`][].
 
-* `url` {string}
-* `context` {Object}
-  * `format` {string}
-* `defaultGetSource` {Function}
-* Returns: {Object}
-  * `source` {string|SharedArrayBuffer|Uint8Array}
+If the source value of a text-based format (i.e., `'json'`, `'module'`)
+is not a string, it is converted to a string using [`util.TextDecoder`][].
 
-The `getSource` hook provides a way to define a custom method for retrieving
-the source code of an ES module specifier. This would allow a loader to
-potentially avoid reading files from disk.
+The `load` hook provides a way to define a custom method for retrieving the
+source code of an ES module specifier. This would allow a loader to potentially
+avoid reading files from disk. It could also be used to map an unrecognized
+format to a supported one, for example `yaml` to `module`.
 
 ```js
 /**
  * @param {string} url
- * @param {{ format: string }} context
- * @param {Function} defaultGetSource
- * @returns {Promise<{ source: !(string | SharedArrayBuffer | Uint8Array) }>}
+ * @param {{
+    format: string,
+  }} context If resolve settled with a `format`, that value is included here.
+ * @param {Function} defaultLoad
+ * @returns {Promise<{
+    format: !string,
+    source: !(string | ArrayBuffer | SharedArrayBuffer | Uint8Array),
+  }>}
  */
-export async function getSource(url, context, defaultGetSource) {
+export async function load(url, context, defaultLoad) {
   const { format } = context;
   if (Math.random() > 0.5) { // Some condition.
-    // For some or all URLs, do some custom logic for retrieving the source.
-    // Always return an object of the form {source: <string|buffer>}.
+    /*
+      For some or all URLs, do some custom logic for retrieving the source.
+      Always return an object of the form {
+        format: <string>,
+        source: <string|buffer>,
+      }.
+    */
     return {
+      format,
       source: '...',
     };
   }
   // Defer to Node.js for all other URLs.
-  return defaultGetSource(url, context, defaultGetSource);
+  return defaultLoad(url, context, defaultLoad);
 }
 ```
 
-#### `transformSource(source, context, defaultTransformSource)`
+In a more advanced scenario, this can also be used to transform an unsupported
+source to a supported one (see [Examples](#examples) below).
 
-> Note: The loaders API is being redesigned. This hook may disappear or its
-> signature may change. Do not rely on the API described below.
-
-* `source` {string|SharedArrayBuffer|Uint8Array}
-* `context` {Object}
-  * `format` {string}
-  * `url` {string}
-* Returns: {Object}
-  * `source` {string|SharedArrayBuffer|Uint8Array}
-
-The `transformSource` hook provides a way to modify the source code of a loaded
-ES module file after the source string has been loaded but before Node.js has
-done anything with it.
-
-If this hook is used to convert unknown-to-Node.js file types into executable
-JavaScript, a resolve hook is also necessary in order to register any
-unknown-to-Node.js file extensions. See the [transpiler loader example][] below.
-
-```js
-/**
- * @param {!(string | SharedArrayBuffer | Uint8Array)} source
- * @param {{
- *   format: string,
- *   url: string,
- * }} context
- * @param {Function} defaultTransformSource
- * @returns {Promise<{ source: !(string | SharedArrayBuffer | Uint8Array) }>}
- */
-export async function transformSource(source, context, defaultTransformSource) {
-  const { url, format } = context;
-  if (Math.random() > 0.5) { // Some condition.
-    // For some or all URLs, do some custom logic for modifying the source.
-    // Always return an object of the form {source: <string|buffer>}.
-    return {
-      source: '...',
-    };
-  }
-  // Defer to Node.js for all other sources.
-  return defaultTransformSource(source, context, defaultTransformSource);
-}
-```
-
-#### `getGlobalPreloadCode()`
+#### `globalPreload()`
 
 > Note: The loaders API is being redesigned. This hook may disappear or its
 > signature may change. Do not rely on the API described below.
 
+> Note: In a previous version of this API, this hook was named
+> `getGlobalPreloadCode`.
+
 * Returns: {string}
 
-Sometimes it might be necessary to run some code inside of the same global scope
-that the application runs in. This hook allows the return of a string that is
-run as sloppy-mode script on startup.
+Sometimes it might be necessary to run some code inside of the same global
+scope that the application runs in. This hook allows the return of a string
+that is run as a sloppy-mode script on startup.
 
 Similar to how CommonJS wrappers work, the code runs in an implicit function
 scope. The only argument is a `require`-like function that can be used to load
@@ -815,7 +790,7 @@ its own `require` using  `module.createRequire()`.
 /**
  * @returns {string} Code to run before application startup
  */
-export function getGlobalPreloadCode() {
+export function globalPreload() {
   return `\
 globalThis.someInjectedProperty = 42;
 console.log('I just set some globals!');
@@ -867,19 +842,7 @@ export function resolve(specifier, context, defaultResolve) {
   return defaultResolve(specifier, context, defaultResolve);
 }
 
-export function getFormat(url, context, defaultGetFormat) {
-  // This loader assumes all network-provided JavaScript is ES module code.
-  if (url.startsWith('https://')) {
-    return {
-      format: 'module'
-    };
-  }
-
-  // Let Node.js handle all other URLs.
-  return defaultGetFormat(url, context, defaultGetFormat);
-}
-
-export function getSource(url, context, defaultGetSource) {
+export function load(url, context, defaultLoad) {
   // For JavaScript to be loaded over the network, we need to fetch and
   // return it.
   if (url.startsWith('https://')) {
@@ -887,13 +850,18 @@ export function getSource(url, context, defaultGetSource) {
       get(url, (res) => {
         let data = '';
         res.on('data', (chunk) => data += chunk);
-        res.on('end', () => resolve({ source: data }));
+        res.on('end', () => resolve({
+          // This example assumes all network-provided JavaScript is ES module
+          // code.
+          format: 'module',
+          source: data,
+        }));
       }).on('error', (err) => reject(err));
     });
   }
 
   // Let Node.js handle all other URLs.
-  return defaultGetSource(url, context, defaultGetSource);
+  return defaultLoad(url, context, defaultLoad);
 }
 ```
 
@@ -912,9 +880,9 @@ prints the current version of CoffeeScript per the module at the URL in
 #### Transpiler loader
 
 Sources that are in formats Node.js doesn’t understand can be converted into
-JavaScript using the [`transformSource` hook][]. Before that hook gets called,
-however, other hooks need to tell Node.js not to throw an error on unknown file
-types; and to tell Node.js how to load this new file type.
+JavaScript using the [`load` hook][load hook]. Before that hook gets called,
+however, a [`resolve` hook][resolve hook] hook needs to tell Node.js not to
+throw an error on unknown file types.
 
 This is less performant than transpiling source files before running
 Node.js; a transpiler loader should only be used for development and testing
@@ -922,16 +890,21 @@ purposes.
 
 ```js
 // coffeescript-loader.mjs
-import { URL, pathToFileURL } from 'url';
-import CoffeeScript from 'coffeescript';
+import { readFile } from 'fs/promises';
+import { readFileSync } from 'fs';
+import { createRequire } from 'module';
+import { dirname, extname, resolve as resolvePath } from 'path';
 import { cwd } from 'process';
+import { fileURLToPath, pathToFileURL } from 'url';
 
-const baseURL = pathToFileURL(`${cwd()}/`).href;
+import CoffeeScript from 'coffeescript';
+
+const baseURL = pathToFileURL(`${cwd}/`).href;
 
 // CoffeeScript files end in .coffee, .litcoffee or .coffee.md.
 const extensionsRegex = /\.coffee$|\.litcoffee$|\.coffee\.md$/;
 
-export function resolve(specifier, context, defaultResolve) {
+export async function resolve(specifier, context, defaultResolve) {
   const { parentURL = baseURL } = context;
 
   // Node.js normally errors on unknown file extensions, so return a URL for
@@ -946,31 +919,72 @@ export function resolve(specifier, context, defaultResolve) {
   return defaultResolve(specifier, context, defaultResolve);
 }
 
-export function getFormat(url, context, defaultGetFormat) {
+export async function load(url, context, defaultLoad) {
   // Now that we patched resolve to let CoffeeScript URLs through, we need to
-  // tell Node.js what format such URLs should be interpreted as. For the
-  // purposes of this loader, all CoffeeScript URLs are ES modules.
+  // tell Node.js what format such URLs should be interpreted as. Because
+  // CoffeeScript transpiles into JavaScript, it should be one of the two
+  // JavaScript formats: 'commonjs' or 'module'.
   if (extensionsRegex.test(url)) {
+    // CoffeeScript files can be either CommonJS or ES modules, so we want any
+    // CoffeeScript file to be treated by Node.js the same as a .js file at the
+    // same location. To determine how Node.js would interpret an arbitrary .js
+    // file, search up the file system for the nearest parent package.json file
+    // and read its "type" field.
+    const format = await getPackageType(url);
+    // When a hook returns a format of 'commonjs', `source` is be ignored.
+    // To handle CommonJS files, a handler needs to be registered with
+    // `require.extensions` in order to process the files with the CommonJS
+    // loader. Avoiding the need for a separate CommonJS handler is a future
+    // enhancement planned for ES module loaders.
+    if (format === 'commonjs') {
+      return { format };
+    }
+
+    const { source: rawSource } = await defaultLoad(url, { format });
+    // This hook converts CoffeeScript source code into JavaScript source code
+    // for all imported CoffeeScript files.
+    const transformedSource = CoffeeScript.compile(rawSource.toString(), {
+      bare: true,
+      filename: url,
+    });
+
     return {
-      format: 'module'
+      format,
+      source: transformedSource,
     };
   }
 
   // Let Node.js handle all other URLs.
-  return defaultGetFormat(url, context, defaultGetFormat);
+  return defaultLoad(url, context, defaultLoad);
 }
 
-export function transformSource(source, context, defaultTransformSource) {
-  const { url, format } = context;
-
-  if (extensionsRegex.test(url)) {
-    return {
-      source: CoffeeScript.compile(source, { bare: true })
-    };
-  }
-
-  // Let Node.js handle all other sources.
-  return defaultTransformSource(source, context, defaultTransformSource);
+async function getPackageType(url) {
+  // `url` is only a file path during the first iteration when passed the
+  // resolved url from the load() hook
+  // an actual file path from load() will contain a file extension as it's
+  // required by the spec
+  // this simple truthy check for whether `url` contains a file extension will
+  // work for most projects but does not cover some edge-cases (such as
+  // extension-less files or a url ending in a trailing space)
+  const isFilePath = !!extname(url);
+  // If it is a file path, get the directory it's in
+  const dir = isFilePath ?
+    dirname(fileURLToPath(url)) :
+    url;
+  // Compose a file path to a package.json in the same directory,
+  // which may or may not exist
+  const packagePath = resolvePath(dir, 'package.json');
+  // Try to read the possibly non-existant package.json
+  const type = await readFile(packagePath, { encoding: 'utf8' })
+    .then((filestring) => JSON.parse(filestring).type)
+    .catch((err) => {
+      if (err?.code !== 'ENOENT') console.error(err);
+    });
+  // Ff package.json existed and contained a `type` field with a value, voila
+  if (type) return type;
+  // Otherwise, (if not at the root) continue checking the next directory up
+  // If at the root, stop and return false
+  return dir.length > 1 && getPackageType(resolvePath(dir, '..'));
 }
 ```
 
@@ -1377,11 +1391,11 @@ success!
 [`package.json`]: packages.md#nodejs-packagejson-field-definitions
 [`process.dlopen`]: process.md#processdlopenmodule-filename-flags
 [`string`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String
-[`transformSource` hook]: #transformsourcesource-context-defaulttransformsource
 [`util.TextDecoder`]: util.md#class-utiltextdecoder
 [cjs-module-lexer]: https://github.com/guybedford/cjs-module-lexer/tree/1.2.2
 [custom https loader]: #https-loader
+[load hook]: #loadurl-context-defaultload
+[resolve hook]: #resolvespecifier-context-defaultresolve
 [special scheme]: https://url.spec.whatwg.org/#special-scheme
 [the official standard format]: https://tc39.github.io/ecma262/#sec-modules
-[transpiler loader example]: #transpiler-loader
 [url.pathToFileURL]: url.md#urlpathtofileurlpath
diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
index 3f1dac356b81f4..b8eff0440624a4 100644
--- a/lib/internal/modules/cjs/loader.js
+++ b/lib/internal/modules/cjs/loader.js
@@ -981,14 +981,14 @@ Module.prototype.load = function(filename) {
   Module._extensions[extension](this, filename);
   this.loaded = true;
 
-  const ESMLoader = asyncESM.ESMLoader;
+  const esmLoader = asyncESM.esmLoader;
   // Create module entry at load time to snapshot exports correctly
   const exports = this.exports;
   // Preemptively cache
   if ((module?.module === undefined ||
        module.module.getStatus() < kEvaluated) &&
-      !ESMLoader.cjsCache.has(this))
-    ESMLoader.cjsCache.set(this, exports);
+      !esmLoader.cjsCache.has(this))
+    esmLoader.cjsCache.set(this, exports);
 };
 
 
@@ -1022,7 +1022,7 @@ function wrapSafe(filename, content, cjsModuleInstance) {
       lineOffset: 0,
       displayErrors: true,
       importModuleDynamically: async (specifier) => {
-        const loader = asyncESM.ESMLoader;
+        const loader = asyncESM.esmLoader;
         return loader.import(specifier, normalizeReferrerURL(filename));
       },
     });
@@ -1037,7 +1037,7 @@ function wrapSafe(filename, content, cjsModuleInstance) {
     ], {
       filename,
       importModuleDynamically(specifier) {
-        const loader = asyncESM.ESMLoader;
+        const loader = asyncESM.esmLoader;
         return loader.import(specifier, normalizeReferrerURL(filename));
       },
     });
diff --git a/lib/internal/modules/esm/get_format.js b/lib/internal/modules/esm/get_format.js
index f02bb5cde70772..7c07e5b1f7ce17 100644
--- a/lib/internal/modules/esm/get_format.js
+++ b/lib/internal/modules/esm/get_format.js
@@ -1,7 +1,9 @@
 'use strict';
 const {
+  ObjectAssign,
+  ObjectCreate,
+  ObjectPrototypeHasOwnProperty,
   RegExpPrototypeExec,
-  StringPrototypeStartsWith,
 } = primordials;
 const { extname } = require('path');
 const { getOptionValue } = require('internal/options');
@@ -36,26 +38,25 @@ if (experimentalWasmModules)
 if (experimentalJsonModules)
   extensionFormatMap['.json'] = legacyExtensionFormatMap['.json'] = 'json';
 
-function defaultGetFormat(url, context, defaultGetFormatUnused) {
-  if (StringPrototypeStartsWith(url, 'node:')) {
-    return { format: 'builtin' };
-  }
-  const parsed = new URL(url);
-  if (parsed.protocol === 'data:') {
+const protocolHandlers = ObjectAssign(ObjectCreate(null), {
+  'data:'(parsed) {
     const { 1: mime } = RegExpPrototypeExec(
       /^([^/]+\/[^;,]+)(?:[^,]*?)(;base64)?,/,
       parsed.pathname,
-    ) || [ , null ];
+    ) || [, null];
     const format = ({
       '__proto__': null,
       'text/javascript': 'module',
       'application/json': experimentalJsonModules ? 'json' : null,
       'application/wasm': experimentalWasmModules ? 'wasm' : null
     })[mime] || null;
-    return { format };
-  } else if (parsed.protocol === 'file:') {
+
+    return format;
+  },
+  'file:'(parsed, url) {
     const ext = extname(parsed.pathname);
     let format;
+
     if (ext === '.js') {
       format = getPackageType(parsed.href) === 'module' ? 'module' : 'commonjs';
     } else {
@@ -71,9 +72,18 @@ function defaultGetFormat(url, context, defaultGetFormatUnused) {
         throw new ERR_UNKNOWN_FILE_EXTENSION(ext, fileURLToPath(url));
       }
     }
-    return { format: format || null };
-  }
-  return { format: null };
+
+    return format || null;
+  },
+  'node:'() { return 'builtin'; },
+});
+
+function defaultGetFormat(url, context) {
+  const parsed = new URL(url);
+
+  return ObjectPrototypeHasOwnProperty(protocolHandlers, parsed.protocol) ?
+    protocolHandlers[parsed.protocol](parsed, url) :
+    null;
 }
 
 module.exports = {
diff --git a/lib/internal/modules/esm/get_source.js b/lib/internal/modules/esm/get_source.js
index 092f61c0b00900..8281a8e4876aa0 100644
--- a/lib/internal/modules/esm/get_source.js
+++ b/lib/internal/modules/esm/get_source.js
@@ -40,6 +40,6 @@ async function defaultGetSource(url, { format } = {}, defaultGetSource) {
   if (policy?.manifest) {
     policy.manifest.assertIntegrity(parsed, source);
   }
-  return { source };
+  return source;
 }
 exports.defaultGetSource = defaultGetSource;
diff --git a/lib/internal/modules/esm/load.js b/lib/internal/modules/esm/load.js
new file mode 100644
index 00000000000000..38785e78f338ce
--- /dev/null
+++ b/lib/internal/modules/esm/load.js
@@ -0,0 +1,32 @@
+'use strict';
+
+const { defaultGetFormat } = require('internal/modules/esm/get_format');
+const { defaultGetSource } = require('internal/modules/esm/get_source');
+const { translators } = require('internal/modules/esm/translators');
+
+async function defaultLoad(url, context) {
+  let {
+    format,
+    source,
+  } = context;
+
+  if (!translators.has(format)) format = defaultGetFormat(url);
+
+  if (
+    format === 'builtin' ||
+    format === 'commonjs'
+  ) {
+    source = null;
+  } else if (source == null) {
+    source = await defaultGetSource(url, { format });
+  }
+
+  return {
+    format,
+    source,
+  };
+}
+
+module.exports = {
+  defaultLoad,
+};
diff --git a/lib/internal/modules/esm/loader.js b/lib/internal/modules/esm/loader.js
index de9863ed71ce8a..b12a87a9021242 100644
--- a/lib/internal/modules/esm/loader.js
+++ b/lib/internal/modules/esm/loader.js
@@ -4,11 +4,18 @@
 require('internal/modules/cjs/loader');
 
 const {
+  Array,
+  ArrayIsArray,
+  ArrayPrototypeJoin,
+  ArrayPrototypePush,
   FunctionPrototypeBind,
+  FunctionPrototypeCall,
+  ObjectCreate,
   ObjectSetPrototypeOf,
+  PromiseAll,
   RegExpPrototypeExec,
+  SafeArrayIterator,
   SafeWeakMap,
-  StringPrototypeStartsWith,
   globalThis,
 } = primordials;
 
@@ -16,12 +23,15 @@ const {
   ERR_INVALID_ARG_TYPE,
   ERR_INVALID_ARG_VALUE,
   ERR_INVALID_MODULE_SPECIFIER,
-  ERR_INVALID_RETURN_PROPERTY,
   ERR_INVALID_RETURN_PROPERTY_VALUE,
   ERR_INVALID_RETURN_VALUE,
   ERR_UNKNOWN_MODULE_FORMAT
 } = require('internal/errors').codes;
-const { URL, pathToFileURL, isURLInstance } = require('internal/url');
+const { pathToFileURL, isURLInstance } = require('internal/url');
+const {
+  isAnyArrayBuffer,
+  isArrayBufferView,
+} = require('internal/util/types');
 const ModuleMap = require('internal/modules/esm/module_map');
 const ModuleJob = require('internal/modules/esm/module_job');
 
@@ -29,125 +39,159 @@ const {
   defaultResolve,
   DEFAULT_CONDITIONS,
 } = require('internal/modules/esm/resolve');
-const { defaultGetFormat } = require('internal/modules/esm/get_format');
-const { defaultGetSource } = require(
-  'internal/modules/esm/get_source');
-const { defaultTransformSource } = require(
-  'internal/modules/esm/transform_source');
+const { defaultLoad } = require('internal/modules/esm/load');
 const { translators } = require(
   'internal/modules/esm/translators');
 const { getOptionValue } = require('internal/options');
 
-/* A Loader instance is used as the main entry point for loading ES modules.
+/**
+ * An ESMLoader instance is used as the main entry point for loading ES modules.
  * Currently, this is a singleton -- there is only one used for loading
- * the main module and everything in its dependency graph. */
-class Loader {
-  constructor() {
-    // Methods which translate input code or other information
-    // into es modules
-    this.translators = translators;
-
-    // Registry of loaded modules, akin to `require.cache`
-    this.moduleMap = new ModuleMap();
-
-    // Map of already-loaded CJS modules to use
-    this.cjsCache = new SafeWeakMap();
-
-    // This hook is called before the first root module is imported. It's a
-    // function that returns a piece of code that runs as a sloppy-mode script.
-    // The script may evaluate to a function that can be called with a
-    // `getBuiltin` helper that can be used to retrieve builtins.
-    // If the hook returns `null` instead of a source string, it opts out of
-    // running any preload code.
-    // The preload code runs as soon as the hook module has finished evaluating.
-    this._getGlobalPreloadCode = null;
-    // The resolver has the signature
-    //   (specifier : string, parentURL : string, defaultResolve)
-    //       -> Promise<{ url : string }>
-    // where defaultResolve is ModuleRequest.resolve (having the same
-    // signature itself).
-    this._resolve = defaultResolve;
-    // This hook is called after the module is resolved but before a translator
-    // is chosen to load it; the format returned by this function is the name
-    // of a translator.
-    this._getFormat = defaultGetFormat;
-    // This hook is called just before the source code of an ES module file
-    // is loaded.
-    this._getSource = defaultGetSource;
-    // This hook is called just after the source code of an ES module file
-    // is loaded, but before anything is done with the string.
-    this._transformSource = defaultTransformSource;
-    // The index for assigning unique URLs to anonymous module evaluation
-    this.evalIndex = 0;
-  }
+ * the main module and everything in its dependency graph.
+ */
+class ESMLoader {
+  /**
+   * Prior to ESM loading. These are called once before any modules are started.
+   * @private
+   * @property {function[]} globalPreloaders First-in-first-out list of
+   * preload hooks.
+   */
+  #globalPreloaders = [];
 
-  async resolve(specifier, parentURL) {
-    const isMain = parentURL === undefined;
-    if (!isMain && typeof parentURL !== 'string' && !isURLInstance(parentURL))
-      throw new ERR_INVALID_ARG_TYPE('parentURL', ['string', 'URL'], parentURL);
+  /**
+   * Phase 2 of 2 in ESM loading.
+   * @private
+   * @property {function[]} loaders First-in-first-out list of loader hooks.
+   */
+  #loaders = [
+    defaultLoad,
+  ];
 
-    const resolveResponse = await this._resolve(
-      specifier, { parentURL, conditions: DEFAULT_CONDITIONS }, defaultResolve);
-    if (typeof resolveResponse !== 'object') {
-      throw new ERR_INVALID_RETURN_VALUE(
-        'object', 'loader resolve', resolveResponse);
-    }
+  /**
+   * Phase 1 of 2 in ESM loading.
+   * @private
+   * @property {function[]} resolvers First-in-first-out list of resolver hooks
+   */
+  #resolvers = [
+    defaultResolve,
+  ];
 
-    const { url } = resolveResponse;
-    if (typeof url !== 'string') {
-      throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
-        'string', 'loader resolve', 'url', url);
-    }
-    return url;
-  }
+  /**
+   * Map of already-loaded CJS modules to use
+   */
+  cjsCache = new SafeWeakMap();
 
-  async getFormat(url) {
-    const getFormatResponse = await this._getFormat(
-      url, {}, defaultGetFormat);
-    if (typeof getFormatResponse !== 'object') {
-      throw new ERR_INVALID_RETURN_VALUE(
-        'object', 'loader getFormat', getFormatResponse);
-    }
+  /**
+   * The index for assigning unique URLs to anonymous module evaluation
+   */
+  evalIndex = 0;
 
-    const { format } = getFormatResponse;
-    if (format === null) {
-      const dataUrl = RegExpPrototypeExec(
-        /^data:([^/]+\/[^;,]+)(?:[^,]*?)(;base64)?,/,
-        url,
+  /**
+   * Registry of loaded modules, akin to `require.cache`
+   */
+  moduleMap = new ModuleMap();
+
+  /**
+   * Methods which translate input code or other information into ES modules
+   */
+  translators = translators;
+
+  static pluckHooks({
+    globalPreload,
+    resolve,
+    load,
+    // obsolete hooks:
+    dynamicInstantiate,
+    getFormat,
+    getGlobalPreloadCode,
+    getSource,
+    transformSource,
+  }) {
+    const obsoleteHooks = [];
+    const acceptedHooks = ObjectCreate(null);
+
+    if (getGlobalPreloadCode) {
+      globalPreload ??= getGlobalPreloadCode;
+
+      process.emitWarning(
+        'Loader hook "getGlobalPreloadCode" has been renamed to "globalPreload"'
       );
-      throw new ERR_INVALID_MODULE_SPECIFIER(
-        url,
-        dataUrl ? `has an unsupported MIME type "${dataUrl[1]}"` : '');
-    }
-    if (typeof format !== 'string') {
-      throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
-        'string', 'loader getFormat', 'format', format);
     }
+    if (dynamicInstantiate) ArrayPrototypePush(
+      obsoleteHooks,
+      'dynamicInstantiate'
+    );
+    if (getFormat) ArrayPrototypePush(
+      obsoleteHooks,
+      'getFormat',
+    );
+    if (getSource) ArrayPrototypePush(
+      obsoleteHooks,
+      'getSource',
+    );
+    if (transformSource) ArrayPrototypePush(
+      obsoleteHooks,
+      'transformSource',
+    );
 
-    if (format === 'builtin') {
-      return format;
-    }
+    if (obsoleteHooks.length) process.emitWarning(
+      `Obsolete loader hook(s) supplied and will be ignored: ${
+        ArrayPrototypeJoin(obsoleteHooks, ', ')
+      }`,
+      'DeprecationWarning',
+    );
 
-    if (this._resolve !== defaultResolve) {
-      try {
-        new URL(url);
-      } catch {
-        throw new ERR_INVALID_RETURN_PROPERTY(
-          'url', 'loader resolve', 'url', url
-        );
-      }
+    // Use .bind() to avoid giving access to the Loader instance when called.
+    if (globalPreload) {
+      acceptedHooks.globalPreloader =
+        FunctionPrototypeBind(globalPreload, null);
+    }
+    if (resolve) {
+      acceptedHooks.resolver = FunctionPrototypeBind(resolve, null);
+    }
+    if (load) {
+      acceptedHooks.loader = FunctionPrototypeBind(load, null);
     }
 
-    if (this._resolve === defaultResolve &&
-      !StringPrototypeStartsWith(url, 'file:') &&
-      !StringPrototypeStartsWith(url, 'data:')
-    ) {
-      throw new ERR_INVALID_RETURN_PROPERTY(
-        'file: or data: url', 'loader resolve', 'url', url
+    return acceptedHooks;
+  }
+
+  /**
+   * Collect custom/user-defined hook(s). After all hooks have been collected,
+   * calls global preload hook(s).
+   * @param {object | object[]} customLoaders A list of exports from
+   * user-defined loaders (as returned by ESMLoader.import()).
+   */
+  async addCustomLoaders(
+    customLoaders = [],
+  ) {
+    if (!ArrayIsArray(customLoaders)) customLoaders = [customLoaders];
+
+    for (let i = 0; i < customLoaders.length; i++) {
+      const exports = customLoaders[i];
+      const {
+        globalPreloader,
+        resolver,
+        loader,
+      } = ESMLoader.pluckHooks(exports);
+
+      if (globalPreloader) ArrayPrototypePush(
+        this.#globalPreloaders,
+        FunctionPrototypeBind(globalPreloader, null), // [1]
+      );
+      if (resolver) ArrayPrototypePush(
+        this.#resolvers,
+        FunctionPrototypeBind(resolver, null), // [1]
+      );
+      if (loader) ArrayPrototypePush(
+        this.#loaders,
+        FunctionPrototypeBind(loader, null), // [1]
       );
     }
 
-    return format;
+    // [1] ensure hook function is not bound to ESMLoader instance
+
+    this.preload();
   }
 
   async eval(
@@ -168,100 +212,259 @@ class Loader {
     const job = new ModuleJob(this, url, evalInstance, false, false);
     this.moduleMap.set(url, job);
     const { module } = await job.run();
+
     return {
       namespace: module.getNamespace(),
     };
   }
 
-  async import(specifier, parent) {
-    const job = await this.getModuleJob(specifier, parent);
-    const { module } = await job.run();
-    return module.getNamespace();
+  async getModuleJob(specifier, parentURL) {
+    const { format, url } = await this.resolve(specifier, parentURL);
+    let job = this.moduleMap.get(url);
+    // CommonJS will set functions for lazy job evaluation.
+    if (typeof job === 'function') this.moduleMap.set(url, job = job());
+
+    if (job !== undefined) return job;
+
+    const moduleProvider = async (url, isMain) => {
+      const { format: finalFormat, source } = await this.load(url, { format });
+
+      const translator = translators.get(finalFormat);
+
+      if (!translator) throw new ERR_UNKNOWN_MODULE_FORMAT(finalFormat);
+
+      return FunctionPrototypeCall(translator, this, url, source, isMain);
+    };
+
+    const inspectBrk = (
+      parentURL === undefined &&
+      getOptionValue('--inspect-brk')
+    );
+
+    job = new ModuleJob(
+      this,
+      url,
+      moduleProvider,
+      parentURL === undefined,
+      inspectBrk
+    );
+
+    this.moduleMap.set(url, job);
+
+    return job;
   }
 
-  hook(hooks) {
-    const {
-      resolve,
-      dynamicInstantiate,
-      getFormat,
-      getSource,
-      transformSource,
-      getGlobalPreloadCode,
-    } = hooks;
+  /**
+   * This method is usually called indirectly as part of the loading processes.
+   * Internally, it is used directly to add loaders. Use directly with caution.
+   *
+   * This method must NOT be renamed: it functions as a dynamic import on a
+   * loader module.
+   *
+   * @param {string | string[]} specifiers Path(s) to the module
+   * @param {string} [parentURL] Path of the parent importing the module
+   * @returns {object | object[]} A list of module export(s)
+   */
+  async import(specifiers, parentURL) {
+    const wasArr = ArrayIsArray(specifiers);
+    if (!wasArr) specifiers = [specifiers];
 
-    // Use .bind() to avoid giving access to the Loader instance when called.
-    if (resolve !== undefined)
-      this._resolve = FunctionPrototypeBind(resolve, null);
-    if (dynamicInstantiate !== undefined) {
-      process.emitWarning(
-        'The dynamicInstantiate loader hook has been removed.');
-    }
-    if (getFormat !== undefined) {
-      this._getFormat = FunctionPrototypeBind(getFormat, null);
-    }
-    if (getSource !== undefined) {
-      this._getSource = FunctionPrototypeBind(getSource, null);
-    }
-    if (transformSource !== undefined) {
-      this._transformSource = FunctionPrototypeBind(transformSource, null);
-    }
-    if (getGlobalPreloadCode !== undefined) {
-      this._getGlobalPreloadCode =
-        FunctionPrototypeBind(getGlobalPreloadCode, null);
+    const count = specifiers.length;
+    const jobs = new Array(count);
+
+    for (let i = 0; i < count; i++) {
+      jobs[i] = this.getModuleJob(specifiers[i], parentURL)
+        .then((job) => job.run())
+        .then(({ module }) => module.getNamespace());
     }
+
+    const namespaces = await PromiseAll(new SafeArrayIterator(jobs));
+
+    return wasArr ?
+      namespaces :
+      namespaces[0];
   }
 
-  runGlobalPreloadCode() {
-    if (!this._getGlobalPreloadCode) {
-      return;
+  /**
+   * Provide source that is understood by one of Node's translators.
+   *
+   * The internals of this WILL change when chaining is implemented,
+   * depending on the resolution/consensus from #36954
+   * @param {string} url The URL/path of the module to be loaded
+   * @param {Object} context Metadata about the module
+   * @returns {Object}
+   */
+  async load(url, context = {}) {
+    const defaultLoader = this.#loaders[0];
+
+    const loader = this.#loaders.length === 1 ?
+      defaultLoader :
+      this.#loaders[1];
+    const loaded = await loader(url, context, defaultLoader);
+
+    if (typeof loaded !== 'object') {
+      throw new ERR_INVALID_RETURN_VALUE(
+        'object',
+        'loader load',
+        loaded,
+      );
     }
-    const preloadCode = this._getGlobalPreloadCode();
-    if (preloadCode === null) {
-      return;
+
+    const {
+      format,
+      source,
+    } = loaded;
+
+    if (format == null) {
+      const dataUrl = RegExpPrototypeExec(
+        /^data:([^/]+\/[^;,]+)(?:[^,]*?)(;base64)?,/,
+        url,
+      );
+
+      throw new ERR_INVALID_MODULE_SPECIFIER(
+        url,
+        dataUrl ? `has an unsupported MIME type "${dataUrl[1]}"` : ''
+      );
     }
 
-    if (typeof preloadCode !== 'string') {
-      throw new ERR_INVALID_RETURN_VALUE(
-        'string', 'loader getGlobalPreloadCode', preloadCode);
+    if (typeof format !== 'string') {
+      throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
+        'string',
+        'loader resolve',
+        'format',
+        format,
+      );
     }
-    const { compileFunction } = require('vm');
-    const preloadInit = compileFunction(preloadCode, ['getBuiltin'], {
-      filename: '<preload>',
-    });
-    const { NativeModule } = require('internal/bootstrap/loaders');
-
-    preloadInit.call(globalThis, (builtinName) => {
-      if (NativeModule.canBeRequiredByUsers(builtinName)) {
-        return require(builtinName);
+
+    if (
+      source != null &&
+      typeof source !== 'string' &&
+      !isAnyArrayBuffer(source) &&
+      !isArrayBufferView(source)
+    ) throw ERR_INVALID_RETURN_PROPERTY_VALUE(
+      'string, an ArrayBuffer, or a TypedArray',
+      'loader load',
+      'source',
+      source
+    );
+
+    return {
+      format,
+      source,
+    };
+  }
+
+  preload() {
+    const count = this.#globalPreloaders.length;
+    if (!count) return;
+
+    for (let i = 0; i < count; i++) {
+      const preload = this.#globalPreloaders[i]();
+
+      if (preload == null) return;
+
+      if (typeof preload !== 'string') {
+        throw new ERR_INVALID_RETURN_VALUE(
+          'string',
+          'loader globalPreloadCode',
+          preload,
+        );
       }
-      throw new ERR_INVALID_ARG_VALUE('builtinName', builtinName);
-    });
+      const { compileFunction } = require('vm');
+      const preloadInit = compileFunction(
+        preload,
+        ['getBuiltin'],
+        {
+          filename: '<preload>',
+        }
+      );
+      const { NativeModule } = require('internal/bootstrap/loaders');
+
+      FunctionPrototypeCall(preloadInit, globalThis, (builtinName) => {
+        if (NativeModule.canBeRequiredByUsers(builtinName)) {
+          return require(builtinName);
+        }
+        throw new ERR_INVALID_ARG_VALUE('builtinName', builtinName);
+      });
+    }
   }
 
-  async getModuleJob(specifier, parentURL) {
-    const url = await this.resolve(specifier, parentURL);
-    const format = await this.getFormat(url);
-    let job = this.moduleMap.get(url);
-    // CommonJS will set functions for lazy job evaluation.
-    if (typeof job === 'function')
-      this.moduleMap.set(url, job = job());
-    if (job !== undefined)
-      return job;
+  /**
+   * Resolve the location of the module.
+   *
+   * The internals of this WILL change when chaining is implemented,
+   * depending on the resolution/consensus from #36954
+   * @param {string} originalSpecifier The specified URL path of the module to
+   * be resolved
+   * @param {String} parentURL The URL path of the module's parent
+   * @returns {{ url: String }}
+   */
+  async resolve(originalSpecifier, parentURL) {
+    const isMain = parentURL === undefined;
 
-    if (!translators.has(format))
-      throw new ERR_UNKNOWN_MODULE_FORMAT(format);
+    if (
+      !isMain &&
+      typeof parentURL !== 'string' &&
+      !isURLInstance(parentURL)
+    ) throw new ERR_INVALID_ARG_TYPE(
+      'parentURL',
+      ['string', 'URL'],
+      parentURL,
+    );
 
-    const loaderInstance = translators.get(format);
+    const conditions = DEFAULT_CONDITIONS;
 
-    const inspectBrk = parentURL === undefined &&
-        format === 'module' && getOptionValue('--inspect-brk');
-    job = new ModuleJob(this, url, loaderInstance, parentURL === undefined,
-                        inspectBrk);
-    this.moduleMap.set(url, job);
-    return job;
+    const defaultResolver = this.#resolvers[0];
+
+    const resolver = this.#resolvers.length === 1 ?
+      defaultResolver :
+      this.#resolvers[1];
+    const resolution = await resolver(
+      originalSpecifier,
+      {
+        conditions,
+        parentURL,
+      },
+      defaultResolver,
+    );
+
+    if (typeof resolution !== 'object') {
+      throw new ERR_INVALID_RETURN_VALUE(
+        'object',
+        'loader resolve',
+        resolution,
+      );
+    }
+
+    const { format, url } = resolution;
+
+    if (
+      format != null &&
+      typeof format !== 'string'
+    ) {
+      throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
+        'string',
+        'loader resolve',
+        'format',
+        format,
+      );
+    }
+    if (typeof url !== 'string') {
+      throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
+        'string',
+        'loader resolve',
+        'url',
+        url,
+      );
+    }
+
+    return {
+      format,
+      url,
+    };
   }
 }
 
-ObjectSetPrototypeOf(Loader.prototype, null);
+ObjectSetPrototypeOf(ESMLoader.prototype, null);
 
-exports.Loader = Loader;
+exports.ESMLoader = ESMLoader;
diff --git a/lib/internal/modules/esm/module_job.js b/lib/internal/modules/esm/module_job.js
index 0ef8ebdeb9245b..2f699376d6eaea 100644
--- a/lib/internal/modules/esm/module_job.js
+++ b/lib/internal/modules/esm/module_job.js
@@ -141,9 +141,11 @@ class ModuleJob {
         const { 1: childSpecifier, 2: name } = StringPrototypeMatch(
           e.message,
           /module '(.*)' does not provide an export named '(.+)'/);
-        const childFileURL =
-            await this.loader.resolve(childSpecifier, parentFileUrl);
-        const format = await this.loader.getFormat(childFileURL);
+        const { url: childFileURL } = await this.loader.resolve(
+          childSpecifier, parentFileUrl,
+        );
+        const { format } = await this.loader.load(childFileURL);
+
         if (format === 'commonjs') {
           const importStatement = splitStack[1];
           // TODO(@ctavan): The original error stack only provides the single
@@ -152,7 +154,7 @@ class ModuleJob {
           // just parsing the error stack.
           const oneLineNamedImports = StringPrototypeMatch(importStatement, /{.*}/);
           const destructuringAssignment = oneLineNamedImports &&
-              StringPrototypeReplace(oneLineNamedImports, /\s+as\s+/g, ': ');
+            StringPrototypeReplace(oneLineNamedImports, /\s+as\s+/g, ': ');
           e.message = `Named export '${name}' not found. The requested module` +
             ` '${childSpecifier}' is a CommonJS module, which may not support` +
             ' all module.exports as named exports.\nCommonJS modules can ' +
diff --git a/lib/internal/modules/esm/resolve.js b/lib/internal/modules/esm/resolve.js
index 1b84fe9f87b773..b0a7cec5c59a3f 100644
--- a/lib/internal/modules/esm/resolve.js
+++ b/lib/internal/modules/esm/resolve.js
@@ -130,7 +130,7 @@ function emitTrailingSlashPatternDeprecation(match, pjsonUrl, isExports, base) {
  * @returns
  */
 function emitLegacyIndexDeprecation(url, packageJSONUrl, base, main) {
-  const { format } = defaultGetFormat(url);
+  const format = defaultGetFormat(url);
   if (format !== 'module')
     return;
   const path = fileURLToPath(url);
diff --git a/lib/internal/modules/esm/transform_source.js b/lib/internal/modules/esm/transform_source.js
deleted file mode 100644
index 2d07dd3607fb66..00000000000000
--- a/lib/internal/modules/esm/transform_source.js
+++ /dev/null
@@ -1,7 +0,0 @@
-'use strict';
-
-function defaultTransformSource(source, { url, format } = {},
-                                defaultTransformSource) {
-  return { source };
-}
-exports.defaultTransformSource = defaultTransformSource;
diff --git a/lib/internal/modules/esm/translators.js b/lib/internal/modules/esm/translators.js
index 8b5d8ef3b6ab92..ba00041c417706 100644
--- a/lib/internal/modules/esm/translators.js
+++ b/lib/internal/modules/esm/translators.js
@@ -8,7 +8,7 @@ const {
   ObjectGetPrototypeOf,
   ObjectPrototypeHasOwnProperty,
   ObjectKeys,
-  PromisePrototypeCatch,
+  PromisePrototypeThen,
   PromiseReject,
   SafeArrayIterator,
   SafeMap,
@@ -38,10 +38,6 @@ const {
   cjsParseCache
 } = require('internal/modules/cjs/loader');
 const internalURLModule = require('internal/url');
-const { defaultGetSource } = require(
-  'internal/modules/esm/get_source');
-const { defaultTransformSource } = require(
-  'internal/modules/esm/transform_source');
 const createDynamicModule = require(
   'internal/modules/esm/create_dynamic_module');
 const { fileURLToPath, URL } = require('url');
@@ -112,13 +108,14 @@ function errPath(url) {
 }
 
 async function importModuleDynamically(specifier, { url }) {
-  return asyncESM.ESMLoader.import(specifier, url);
+  return asyncESM.esmLoader.import(specifier, url);
 }
 
 function createImportMetaResolve(defaultParentUrl) {
   return async function resolve(specifier, parentUrl = defaultParentUrl) {
-    return PromisePrototypeCatch(
-      asyncESM.ESMLoader.resolve(specifier, parentUrl),
+    return PromisePrototypeThen(
+      asyncESM.esmLoader.resolve(specifier, parentUrl),
+      ({ url }) => url,
       (error) => (
         error.code === 'ERR_UNSUPPORTED_DIR_IMPORT' ?
           error.url : PromiseReject(error))
@@ -134,12 +131,8 @@ function initializeImportMeta(meta, { url }) {
 }
 
 // Strategy for loading a standard JavaScript module.
-translators.set('module', async function moduleStrategy(url) {
-  let { source } = await this._getSource(
-    url, { format: 'module' }, defaultGetSource);
-  assertBufferSource(source, true, 'getSource');
-  ({ source } = await this._transformSource(
-    source, { url, format: 'module' }, defaultTransformSource));
+translators.set('module', async function moduleStrategy(url, source, isMain) {
+  assertBufferSource(source, true, 'load');
   source = stringify(source);
   maybeCacheSourceMap(url, source);
   debug(`Translating StandardModule ${url}`);
@@ -172,7 +165,8 @@ function enrichCJSError(err, content, filename) {
 // Strategy for loading a node-style CommonJS module
 const isWindows = process.platform === 'win32';
 const winSepRegEx = /\//g;
-translators.set('commonjs', async function commonjsStrategy(url, isMain) {
+translators.set('commonjs', async function commonjsStrategy(url, source,
+                                                            isMain) {
   debug(`Translating CJSModule ${url}`);
 
   let filename = internalURLModule.fileURLToPath(new URL(url));
@@ -188,9 +182,9 @@ translators.set('commonjs', async function commonjsStrategy(url, isMain) {
     debug(`Loading CJSModule ${url}`);
 
     let exports;
-    if (asyncESM.ESMLoader.cjsCache.has(module)) {
-      exports = asyncESM.ESMLoader.cjsCache.get(module);
-      asyncESM.ESMLoader.cjsCache.delete(module);
+    if (asyncESM.esmLoader.cjsCache.has(module)) {
+      exports = asyncESM.esmLoader.cjsCache.get(module);
+      asyncESM.esmLoader.cjsCache.delete(module);
     } else {
       try {
         exports = CJSModule._load(filename, undefined, isMain);
@@ -286,9 +280,9 @@ translators.set('builtin', async function builtinStrategy(url) {
 });
 
 // Strategy for loading a JSON file
-translators.set('json', async function jsonStrategy(url) {
+translators.set('json', async function jsonStrategy(url, source) {
   emitExperimentalWarning('Importing JSON modules');
-  debug(`Translating JSONModule ${url}`);
+  assertBufferSource(source, true, 'load');
   debug(`Loading JSONModule ${url}`);
   const pathname = StringPrototypeStartsWith(url, 'file:') ?
     fileURLToPath(url) : null;
@@ -305,11 +299,6 @@ translators.set('json', async function jsonStrategy(url) {
       });
     }
   }
-  let { source } = await this._getSource(
-    url, { format: 'json' }, defaultGetSource);
-  assertBufferSource(source, true, 'getSource');
-  ({ source } = await this._transformSource(
-    source, { url, format: 'json' }, defaultTransformSource));
   source = stringify(source);
   if (pathname) {
     // A require call could have been called on the same file during loading and
@@ -347,15 +336,13 @@ translators.set('json', async function jsonStrategy(url) {
 });
 
 // Strategy for loading a wasm module
-translators.set('wasm', async function(url) {
+translators.set('wasm', async function(url, source) {
   emitExperimentalWarning('Importing Web Assembly modules');
-  let { source } = await this._getSource(
-    url, { format: 'wasm' }, defaultGetSource);
-  assertBufferSource(source, false, 'getSource');
-  ({ source } = await this._transformSource(
-    source, { url, format: 'wasm' }, defaultTransformSource));
-  assertBufferSource(source, false, 'transformSource');
+
+  assertBufferSource(source, false, 'load');
+
   debug(`Translating WASMModule ${url}`);
+
   let compiled;
   try {
     compiled = await WebAssembly.compile(source);
diff --git a/lib/internal/modules/run_main.js b/lib/internal/modules/run_main.js
index b8238a1dd2c353..d0c08b75e7a524 100644
--- a/lib/internal/modules/run_main.js
+++ b/lib/internal/modules/run_main.js
@@ -41,12 +41,14 @@ function shouldUseESMLoader(mainPath) {
 }
 
 function runMainESM(mainPath) {
-  const esmLoader = require('internal/process/esm_loader');
+  const { loadESM } = require('internal/process/esm_loader');
   const { pathToFileURL } = require('internal/url');
-  handleMainPromise(esmLoader.loadESM((ESMLoader) => {
+
+  handleMainPromise(loadESM((esmLoader) => {
     const main = path.isAbsolute(mainPath) ?
-      pathToFileURL(mainPath).href : mainPath;
-    return ESMLoader.import(main);
+      pathToFileURL(mainPath).href :
+      mainPath;
+    return esmLoader.import(main);
   }));
 }
 
diff --git a/lib/internal/process/esm_loader.js b/lib/internal/process/esm_loader.js
index 8f076b3ef32efd..0f04ca97751ef6 100644
--- a/lib/internal/process/esm_loader.js
+++ b/lib/internal/process/esm_loader.js
@@ -3,7 +3,7 @@
 const {
   ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING,
 } = require('internal/errors').codes;
-const { Loader } = require('internal/modules/esm/loader');
+const { ESMLoader } = require('internal/modules/esm/loader');
 const {
   hasUncaughtExceptionCaptureCallback,
 } = require('internal/process/execution');
@@ -34,38 +34,52 @@ exports.importModuleDynamicallyCallback = async function(wrap, specifier) {
   throw new ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING();
 };
 
-let ESMLoader = new Loader();
-exports.ESMLoader = ESMLoader;
+const esmLoader = new ESMLoader();
 
+exports.esmLoader = esmLoader;
+
+/**
+ * Causes side-effects: user-defined loader hooks are added to esmLoader.
+ * @returns {void}
+ */
 async function initializeLoader() {
   const { getOptionValue } = require('internal/options');
-  const userLoader = getOptionValue('--experimental-loader');
-  if (!userLoader)
-    return;
+  // customLoaders CURRENTLY can be only 1 (a string)
+  // Once chaining is implemented, it will be string[]
+  const customLoaders = getOptionValue('--experimental-loader');
+
+  if (!customLoaders.length) return;
+
+  const { emitExperimentalWarning } = require('internal/util');
+  emitExperimentalWarning('--experimental-loader');
+
   let cwd;
   try {
     cwd = process.cwd() + '/';
   } catch {
     cwd = 'file:///';
   }
-  // If --experimental-loader is specified, create a loader with user hooks.
-  // Otherwise create the default loader.
-  const { emitExperimentalWarning } = require('internal/util');
-  emitExperimentalWarning('--experimental-loader');
-  return (async () => {
-    const hooks =
-        await ESMLoader.import(userLoader, pathToFileURL(cwd).href);
-    ESMLoader = new Loader();
-    ESMLoader.hook(hooks);
-    ESMLoader.runGlobalPreloadCode();
-    return exports.ESMLoader = ESMLoader;
-  })();
+
+  // A separate loader instance is necessary to avoid cross-contamination
+  // between internal Node.js and userland. For example, a module with internal
+  // state (such as a counter) should be independent.
+  const internalEsmLoader = new ESMLoader();
+
+  // Importation must be handled by internal loader to avoid poluting userland
+  const exports = await internalEsmLoader.import(
+    customLoaders,
+    pathToFileURL(cwd).href,
+  );
+
+  // Hooks must then be added to external/public loader
+  // (so they're triggered in userland)
+  await esmLoader.addCustomLoaders(exports);
 }
 
 exports.loadESM = async function loadESM(callback) {
   try {
     await initializeLoader();
-    await callback(ESMLoader);
+    await callback(esmLoader);
   } catch (err) {
     if (hasUncaughtExceptionCaptureCallback()) {
       process._fatalException(err);
diff --git a/lib/internal/process/execution.js b/lib/internal/process/execution.js
index e2d9898012d2d7..48c525057f7477 100644
--- a/lib/internal/process/execution.js
+++ b/lib/internal/process/execution.js
@@ -83,7 +83,7 @@ function evalScript(name, body, breakFirstLine, print) {
       displayErrors: true,
       [kVmBreakFirstLineSymbol]: !!breakFirstLine,
       async importModuleDynamically(specifier) {
-        const loader = await asyncESM.ESMLoader;
+        const loader = await asyncESM.esmLoader;
         return loader.import(specifier, baseUrl);
       }
     }));
diff --git a/lib/repl.js b/lib/repl.js
index 7ebfd91fd28999..4ee8e24d47588c 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -455,7 +455,7 @@ function REPLServer(prompt,
               filename: file,
               displayErrors: true,
               importModuleDynamically: async (specifier) => {
-                return asyncESM.ESMLoader.import(specifier, parentURL);
+                return asyncESM.esmLoader.import(specifier, parentURL);
               }
             });
           } catch (fallbackError) {
@@ -497,7 +497,7 @@ function REPLServer(prompt,
             filename: file,
             displayErrors: true,
             importModuleDynamically: async (specifier) => {
-              return asyncESM.ESMLoader.import(specifier, parentURL);
+              return asyncESM.esmLoader.import(specifier, parentURL);
             }
           });
         } catch (e) {
diff --git a/test/es-module/test-esm-data-urls.js b/test/es-module/test-esm-data-urls.js
index ba8bd4c95746c0..78cd01b4d55a12 100644
--- a/test/es-module/test-esm-data-urls.js
+++ b/test/es-module/test-esm-data-urls.js
@@ -99,7 +99,7 @@ function createBase64URL(mime, body) {
       await import(plainESMURL);
       common.mustNotCall()();
     } catch (e) {
-      assert.strictEqual(e.code, 'ERR_INVALID_MODULE_SPECIFIER');
+      assert.strictEqual(e.code, 'ERR_INVALID_URL');
     }
   }
   {
diff --git a/test/es-module/test-esm-example-loader.js b/test/es-module/test-esm-example-loader.mjs
similarity index 100%
rename from test/es-module/test-esm-example-loader.js
rename to test/es-module/test-esm-example-loader.mjs
diff --git a/test/es-module/test-esm-get-source-loader.mjs b/test/es-module/test-esm-get-source-loader.mjs
deleted file mode 100644
index 66bac969a47d8f..00000000000000
--- a/test/es-module/test-esm-get-source-loader.mjs
+++ /dev/null
@@ -1,6 +0,0 @@
-// Flags: --experimental-loader ./test/fixtures/es-module-loaders/get-source.mjs
-/* eslint-disable node-core/require-common-first, node-core/required-modules */
-import assert from 'assert';
-import { message } from '../fixtures/es-modules/message.mjs';
-
-assert.strictEqual(message, 'WOOHOO!');
diff --git a/test/es-module/test-esm-loader-get-format.mjs b/test/es-module/test-esm-loader-get-format.mjs
deleted file mode 100644
index 2a252439f91ce4..00000000000000
--- a/test/es-module/test-esm-loader-get-format.mjs
+++ /dev/null
@@ -1,12 +0,0 @@
-// Flags: --experimental-loader ./test/fixtures/es-module-loaders/loader-get-format.mjs
-import { mustCall, mustNotCall } from '../common/index.mjs';
-import assert from 'assert';
-
-import('../fixtures/es-modules/package-type-module/extension.unknown')
-.then(
-  mustCall((ns) => {
-    assert.strictEqual(ns.default, 'unknown');
-  }),
-  // Do not use .catch; want exclusive or
-  mustNotCall(() => {})
-);
diff --git a/test/es-module/test-esm-loader-modulemap.js b/test/es-module/test-esm-loader-modulemap.js
index 2d74cd385be52b..48443de4c270c6 100644
--- a/test/es-module/test-esm-loader-modulemap.js
+++ b/test/es-module/test-esm-loader-modulemap.js
@@ -7,7 +7,7 @@
 require('../common');
 
 const assert = require('assert');
-const { Loader } = require('internal/modules/esm/loader');
+const { ESMLoader } = require('internal/modules/esm/loader');
 const ModuleMap = require('internal/modules/esm/module_map');
 const ModuleJob = require('internal/modules/esm/module_job');
 const createDynamicModule = require(
@@ -15,7 +15,7 @@ const createDynamicModule = require(
 
 const stubModuleUrl = new URL('file://tmp/test');
 const stubModule = createDynamicModule(['default'], stubModuleUrl);
-const loader = new Loader();
+const loader = new ESMLoader();
 const moduleMap = new ModuleMap();
 const moduleJob = new ModuleJob(loader, stubModule.module,
                                 () => new Promise(() => {}));
diff --git a/test/es-module/test-esm-loader-stringify-text.mjs b/test/es-module/test-esm-loader-stringify-text.mjs
index ed9bd5069ebf1d..e66da9491b4cd2 100644
--- a/test/es-module/test-esm-loader-stringify-text.mjs
+++ b/test/es-module/test-esm-loader-stringify-text.mjs
@@ -12,6 +12,34 @@ import('test:ArrayBuffer').then(
   mustCall(),
   mustNotCall('Should accept ArrayBuffers'),
 );
+import('test:BigInt64Array').then(
+  mustCall(),
+  mustNotCall('Should accept BigInt64Array'),
+);
+import('test:BigUint64Array').then(
+  mustCall(),
+  mustNotCall('Should accept BigUint64Array'),
+);
+import('test:Float32Array').then(
+  mustCall(),
+  mustNotCall('Should accept Float32Array'),
+);
+import('test:Float64Array').then(
+  mustCall(),
+  mustNotCall('Should accept Float64Array'),
+);
+import('test:Int8Array').then(
+  mustCall(),
+  mustNotCall('Should accept Int8Array'),
+);
+import('test:Int16Array').then(
+  mustCall(),
+  mustNotCall('Should accept Int16Array'),
+);
+import('test:Int32Array').then(
+  mustCall(),
+  mustNotCall('Should accept Int32Array'),
+);
 import('test:null').then(
   mustNotCall('Should not accept null'),
   mustCall((e) => {
@@ -38,6 +66,18 @@ import('test:String').then(
     assert.strictEqual(e.code, 'ERR_INVALID_RETURN_PROPERTY_VALUE');
   })
 );
+import('test:Uint8ClampedArray').then(
+  mustCall(),
+  mustNotCall('Should accept Uint8ClampedArray'),
+);
+import('test:Uint16Array').then(
+  mustCall(),
+  mustNotCall('Should accept Uint16Array'),
+);
+import('test:Uint32Array').then(
+  mustCall(),
+  mustNotCall('Should accept Uint32Array'),
+);
 import('test:Uint8Array').then(
   mustCall(),
   mustNotCall('Should accept Uint8Arrays'),
diff --git a/test/es-module/test-esm-loader.mjs b/test/es-module/test-esm-loader.mjs
new file mode 100644
index 00000000000000..e19a38cc4231b0
--- /dev/null
+++ b/test/es-module/test-esm-loader.mjs
@@ -0,0 +1,83 @@
+// Flags: --experimental-loader ./test/fixtures/es-module-loaders/hooks-custom.mjs
+import '../common/index.mjs';
+import assert from 'assert';
+
+
+await assert.rejects(
+  import('nonexistent/file.mjs'),
+  { code: 'ERR_MODULE_NOT_FOUND' },
+);
+
+await assert.rejects(
+  import('../fixtures/es-modules/file.unknown'),
+  { code: 'ERR_UNKNOWN_FILE_EXTENSION' },
+);
+
+await assert.rejects(
+  import('esmHook/badReturnVal.mjs'),
+  { code: 'ERR_INVALID_RETURN_VALUE' },
+);
+
+// Nullish values are allowed; booleans are not
+await assert.rejects(
+  import('esmHook/format.false'),
+  { code: 'ERR_INVALID_RETURN_PROPERTY_VALUE' },
+);
+await assert.rejects(
+  import('esmHook/format.true'),
+  { code: 'ERR_INVALID_RETURN_PROPERTY_VALUE' },
+);
+
+await assert.rejects(
+  import('esmHook/badReturnFormatVal.mjs'),
+  { code: 'ERR_INVALID_RETURN_PROPERTY_VALUE' },
+);
+
+await assert.rejects(
+  import('esmHook/unsupportedReturnFormatVal.mjs'),
+  { code: 'ERR_UNKNOWN_MODULE_FORMAT' },
+);
+
+await assert.rejects(
+  import('esmHook/badReturnSourceVal.mjs'),
+  { code: 'ERR_INVALID_RETURN_PROPERTY_VALUE' },
+);
+
+await import('../fixtures/es-module-loaders/js-as-esm.js')
+.then((parsedModule) => {
+  assert.strictEqual(typeof parsedModule, 'object');
+  assert.strictEqual(parsedModule.namedExport, 'named-export');
+});
+
+// The custom loader tells node .ext files are MJS
+await import('../fixtures/es-modules/file.ext')
+.then((parsedModule) => {
+  assert.strictEqual(typeof parsedModule, 'object');
+  const { default: defaultExport } = parsedModule;
+  assert.strictEqual(typeof defaultExport, 'function');
+  assert.strictEqual(defaultExport.name, 'iAmReal');
+  assert.strictEqual(defaultExport(), true);
+});
+
+// The custom loader's resolve hook predetermines the format
+await import('esmHook/preknownFormat.pre')
+.then((parsedModule) => {
+  assert.strictEqual(typeof parsedModule, 'object');
+  assert.strictEqual(parsedModule.default, 'hello world');
+});
+
+// The custom loader provides source even though file does not actually exist
+await import('esmHook/virtual.mjs')
+.then((parsedModule) => {
+  assert.strictEqual(typeof parsedModule, 'object');
+  assert.strictEqual(typeof parsedModule.default, 'undefined');
+  assert.strictEqual(parsedModule.message, 'WOOHOO!');
+});
+
+// Ensure custom loaders have separate context from userland
+// hooks-custom.mjs also increments count (which starts at 0)
+// if both share context, count here would be 2
+await import('../fixtures/es-modules/stateful.mjs')
+.then(({ default: count }) => {
+  assert.strictEqual(count(), 1);
+});
diff --git a/test/es-module/test-esm-resolve-hook.mjs b/test/es-module/test-esm-resolve-hook.mjs
deleted file mode 100644
index 39b11e02739d4b..00000000000000
--- a/test/es-module/test-esm-resolve-hook.mjs
+++ /dev/null
@@ -1,8 +0,0 @@
-// Flags: --experimental-loader ./test/fixtures/es-module-loaders/js-loader.mjs
-/* eslint-disable node-core/require-common-first, node-core/required-modules */
-import { namedExport } from '../fixtures/es-module-loaders/js-as-esm.js';
-import assert from 'assert';
-import ok from '../fixtures/es-modules/test-esm-ok.mjs';
-
-assert(ok);
-assert(namedExport);
diff --git a/test/es-module/test-esm-transform-source-loader.mjs b/test/es-module/test-esm-transform-source-loader.mjs
deleted file mode 100644
index e6d4affea495de..00000000000000
--- a/test/es-module/test-esm-transform-source-loader.mjs
+++ /dev/null
@@ -1,6 +0,0 @@
-// Flags: --experimental-loader ./test/fixtures/es-module-loaders/transform-source.mjs
-/* eslint-disable node-core/require-common-first, node-core/required-modules */
-import assert from 'assert';
-import { message } from '../fixtures/es-modules/message.mjs';
-
-assert.strictEqual(message, 'A MESSAGE');
diff --git a/test/fixtures/es-module-loaders/builtin-named-exports-loader.mjs b/test/fixtures/es-module-loaders/builtin-named-exports-loader.mjs
index f06e9e90ff97c3..f206d7635b3f63 100644
--- a/test/fixtures/es-module-loaders/builtin-named-exports-loader.mjs
+++ b/test/fixtures/es-module-loaders/builtin-named-exports-loader.mjs
@@ -2,7 +2,7 @@ import module from 'module';
 
 const GET_BUILTIN = `$__get_builtin_hole_${Date.now()}`;
 
-export function getGlobalPreloadCode() {
+export function globalPreload() {
   return `Object.defineProperty(globalThis, ${JSON.stringify(GET_BUILTIN)}, {
   value: (builtinName) => {
     return getBuiltin(builtinName);
@@ -13,8 +13,9 @@ export function getGlobalPreloadCode() {
 `;
 }
 
-export function resolve(specifier, context, defaultResolve) {
-  const def = defaultResolve(specifier, context);
+export function resolve(specifier, context, next) {
+  const def = next(specifier, context);
+
   if (def.url.startsWith('node:')) {
     return {
       url: `custom-${def.url}`,
@@ -23,7 +24,7 @@ export function resolve(specifier, context, defaultResolve) {
   return def;
 }
 
-export function getSource(url, context, defaultGetSource) {
+export function load(url, context, next) {
   if (url.startsWith('custom-node:')) {
     const urlObj = new URL(url);
     return {
@@ -31,14 +32,7 @@ export function getSource(url, context, defaultGetSource) {
       format: 'module',
     };
   }
-  return defaultGetSource(url, context);
-}
-
-export function getFormat(url, context, defaultGetFormat) {
-  if (url.startsWith('custom-node:')) {
-    return { format: 'module' };
-  }
-  return defaultGetFormat(url, context, defaultGetFormat);
+  return next(url, context);
 }
 
 function generateBuiltinModule(builtinName) {
diff --git a/test/fixtures/es-module-loaders/get-source.mjs b/test/fixtures/es-module-loaders/get-source.mjs
deleted file mode 100644
index e5a9c65201aa28..00000000000000
--- a/test/fixtures/es-module-loaders/get-source.mjs
+++ /dev/null
@@ -1,10 +0,0 @@
-export async function getSource(url, { format }, defaultGetSource) {
-  if (url.endsWith('fixtures/es-modules/message.mjs')) {
-    // Oh, I’ve got that one in my cache!
-    return {
-      source: `export const message = 'Woohoo!'.toUpperCase();`
-    }
-  } else {
-    return defaultGetSource(url, {format}, defaultGetSource);
-  }
-}
diff --git a/test/fixtures/es-module-loaders/hooks-custom.mjs b/test/fixtures/es-module-loaders/hooks-custom.mjs
new file mode 100644
index 00000000000000..59f49ff9e60c13
--- /dev/null
+++ b/test/fixtures/es-module-loaders/hooks-custom.mjs
@@ -0,0 +1,69 @@
+import count from '../es-modules/stateful.mjs';
+
+
+// Arbitrary instance of manipulating a module's internal state
+// used to assert node-land and user-land have different contexts
+count();
+
+/**
+ * @param {string} url A fully resolved file url.
+ * @param {object} context Additional info.
+ * @param {function} next for now, next is defaultLoad a wrapper for
+ * defaultGetFormat + defaultGetSource
+ * @returns {{ format: string, source: (string|SharedArrayBuffer|Uint8Array) }}
+ */
+export function load(url, context, next) {
+  // Load all .js files as ESM, regardless of package scope
+  if (url.endsWith('.js')) return next(url, {
+    ...context,
+    format: 'module',
+  });
+
+  if (url.endsWith('.ext')) return next(url, {
+    ...context,
+    format: 'module',
+  });
+
+  if (url === 'esmHook/badReturnVal.mjs') return 'export function returnShouldBeObject() {}';
+
+  if (url === 'esmHook/badReturnFormatVal.mjs') return {
+    format: Array(0),
+    source: '',
+  }
+  if (url === 'esmHook/unsupportedReturnFormatVal.mjs') return {
+    format: 'foo', // Not one of the allowable inputs: no translator named 'foo'
+    source: '',
+  }
+
+  if (url === 'esmHook/badReturnSourceVal.mjs') return {
+    format: 'module',
+    source: Array(0),
+  }
+
+  if (url === 'esmHook/preknownFormat.pre') return {
+    format: context.format,
+    source: `const msg = 'hello world'; export default msg;`
+  };
+
+  if (url === 'esmHook/virtual.mjs') return {
+    format: 'module',
+    source: `export const message = 'Woohoo!'.toUpperCase();`,
+  };
+
+  return next(url, context, next);
+}
+
+export function resolve(specifier, context, next) {
+  let format = '';
+
+  if (specifier === 'esmHook/format.false') format = false;
+  if (specifier === 'esmHook/format.true') format = true;
+  if (specifier === 'esmHook/preknownFormat.pre') format = 'module';
+
+  if (specifier.startsWith('esmHook')) return {
+    format,
+    url: specifier,
+  };
+
+  return next(specifier, context, next);
+}
diff --git a/test/fixtures/es-module-loaders/hooks-obsolete.mjs b/test/fixtures/es-module-loaders/hooks-obsolete.mjs
new file mode 100644
index 00000000000000..9d12251923d7e9
--- /dev/null
+++ b/test/fixtures/es-module-loaders/hooks-obsolete.mjs
@@ -0,0 +1,22 @@
+export function dynamicInstantiate() {}
+export function getFormat() {}
+export function getSource() {}
+export function transformSource() {}
+
+
+export function load(url, context, next) {
+	if (url === 'whatever') return {
+		format: 'module',
+		source: '',
+	};
+
+	return next(url, context, next);
+}
+
+export function resolve(specifier, context, next) {
+	if (specifier === 'whatever') return {
+		url: specifier,
+	};
+
+	return next(specifier, context, next);
+}
diff --git a/test/fixtures/es-module-loaders/js-loader.mjs b/test/fixtures/es-module-loaders/js-loader.mjs
deleted file mode 100644
index 2f79475e77e269..00000000000000
--- a/test/fixtures/es-module-loaders/js-loader.mjs
+++ /dev/null
@@ -1,9 +0,0 @@
-export function getFormat(url, context, defaultGetFormat) {
-  // Load all .js files as ESM, regardless of package scope
-  if (url.endsWith('.js')) {
-    return {
-      format: 'module'
-    }
-  }
-  return defaultGetFormat(url, context, defaultGetFormat);
-}
diff --git a/test/fixtures/es-module-loaders/loader-invalid-format.mjs b/test/fixtures/es-module-loaders/loader-invalid-format.mjs
index 55ae1cec8ee926..fc1b84658b76de 100644
--- a/test/fixtures/es-module-loaders/loader-invalid-format.mjs
+++ b/test/fixtures/es-module-loaders/loader-invalid-format.mjs
@@ -7,11 +7,12 @@ export async function resolve(specifier, { parentURL }, defaultResolve) {
   return defaultResolve(specifier, {parentURL}, defaultResolve);
 }
 
-export function getFormat(url, context, defaultGetFormat) {
+export async function load(url, context, next) {
   if (url === 'file:///asdf') {
     return {
-      format: 'esm'
+      format: 'esm',
+      source: '',
     }
   }
-  return defaultGetFormat(url, context, defaultGetFormat);
+  return next(url, context, next);
 }
diff --git a/test/fixtures/es-module-loaders/loader-unknown-builtin-module.mjs b/test/fixtures/es-module-loaders/loader-unknown-builtin-module.mjs
index 4ef089fd6eb3fd..1063f8dfd65f2f 100644
--- a/test/fixtures/es-module-loaders/loader-unknown-builtin-module.mjs
+++ b/test/fixtures/es-module-loaders/loader-unknown-builtin-module.mjs
@@ -1,17 +1,7 @@
-export async function resolve(specifier, { parentURL }, defaultResolve) {
-  if (specifier === 'unknown-builtin-module') {
-    return {
-      url: 'node:unknown-builtin-module'
-    };
-  }
-  return defaultResolve(specifier, {parentURL}, defaultResolve);
-}
+export function resolve(specifier, context, next) {
+  if (specifier === 'unknown-builtin-module') return {
+    url: 'node:unknown-builtin-module'
+  };
 
-export async function getFormat(url, context, defaultGetFormat) {
-  if (url === 'node:unknown-builtin-module') {
-    return {
-      format: 'builtin'
-    };
-  }
-  return defaultGetFormat(url, context, defaultGetFormat);
+  return next(specifier, context, next);
 }
diff --git a/test/fixtures/es-module-loaders/string-sources.mjs b/test/fixtures/es-module-loaders/string-sources.mjs
index 3133231208ce1e..180a356bc81478 100644
--- a/test/fixtures/es-module-loaders/string-sources.mjs
+++ b/test/fixtures/es-module-loaders/string-sources.mjs
@@ -2,29 +2,37 @@ const SOURCES = {
   __proto__: null,
   'test:Array': ['1', '2'], // both `1,2` and `12` are valid ESM
   'test:ArrayBuffer': new ArrayBuffer(0),
+  'test:BigInt64Array': new BigInt64Array(0),
+  'test:BigUint64Array': new BigUint64Array(0),
+  'test:Float32Array': new Float32Array(0),
+  'test:Float64Array': new Float64Array(0),
+  'test:Int8Array': new Int8Array(0),
+  'test:Int16Array': new Int16Array(0),
+  'test:Int32Array': new Int32Array(0),
   'test:null': null,
   'test:Object': {},
   'test:SharedArrayBuffer': new SharedArrayBuffer(0),
   'test:string': '',
   'test:String': new String(''),
   'test:Uint8Array': new Uint8Array(0),
+  'test:Uint8ClampedArray': new Uint8ClampedArray(0),
+  'test:Uint16Array': new Uint16Array(0),
+  'test:Uint32Array': new Uint32Array(0),
   'test:undefined': undefined,
 }
-export function resolve(specifier, context, defaultFn) {
+export function resolve(specifier, context, next) {
   if (specifier.startsWith('test:')) {
     return { url: specifier };
   }
-  return defaultFn(specifier, context);
+  return next(specifier, context);
 }
-export function getFormat(href, context, defaultFn) {
+
+export function load(href, context, next) {
   if (href.startsWith('test:')) {
-    return { format: 'module' };
+    return {
+      format: 'module',
+      source: SOURCES[href],
+    };
   }
-  return defaultFn(href, context);
-}
-export function getSource(href, context, defaultFn) {
-  if (href.startsWith('test:')) {
-    return { source: SOURCES[href] };
-  }
-  return defaultFn(href, context);
+  return next(href, context);
 }
diff --git a/test/fixtures/es-module-loaders/transform-source.mjs b/test/fixtures/es-module-loaders/transform-source.mjs
deleted file mode 100644
index 25d983b64e62ca..00000000000000
--- a/test/fixtures/es-module-loaders/transform-source.mjs
+++ /dev/null
@@ -1,14 +0,0 @@
-export async function transformSource(
-  source, { url, format }, defaultTransformSource) {
-  if (format === 'module') {
-    if (typeof source !== 'string') {
-      source = new TextDecoder().decode(source);
-    }
-    return {
-      source: source.replace(`'A message';`, `'A message'.toUpperCase();`)
-    };
-  } else { // source could be a buffer, e.g. for WASM
-    return defaultTransformSource(
-      source, {url, format}, defaultTransformSource);
-  }
-}
diff --git a/test/fixtures/es-modules/file.ext b/test/fixtures/es-modules/file.ext
new file mode 100644
index 00000000000000..db07b384e169d8
--- /dev/null
+++ b/test/fixtures/es-modules/file.ext
@@ -0,0 +1,3 @@
+// fixtures/es-module-loader.mjs tells node to treat this file like ESM
+
+export default function iAmReal() { return true };
diff --git a/test/fixtures/es-modules/file.unknown b/test/fixtures/es-modules/file.unknown
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/test/fixtures/es-modules/stateful.mjs b/test/fixtures/es-modules/stateful.mjs
new file mode 100644
index 00000000000000..745669c462e60d
--- /dev/null
+++ b/test/fixtures/es-modules/stateful.mjs
@@ -0,0 +1,5 @@
+let counter = 0;
+
+export default function count() {
+	return ++counter;
+}
diff --git a/test/message/esm_display_syntax_error.out b/test/message/esm_display_syntax_error.out
index f1b7ff4e2290ee..3b2a944da08806 100644
--- a/test/message/esm_display_syntax_error.out
+++ b/test/message/esm_display_syntax_error.out
@@ -3,5 +3,6 @@ await async () => 0;
 ^^^^^
 
 SyntaxError: Unexpected reserved word
-    at Loader.moduleStrategy (node:internal/modules/esm/translators:*:*)
+    at ESMLoader.moduleStrategy (node:internal/modules/esm/translators:*:*)
+    at ESMLoader.moduleProvider (node:internal/modules/esm/loader:*:*)
     at async link (node:internal/modules/esm/module_job:*:*)
diff --git a/test/message/esm_display_syntax_error_import.out b/test/message/esm_display_syntax_error_import.out
index ad906af431bf95..62607b93c7c593 100644
--- a/test/message/esm_display_syntax_error_import.out
+++ b/test/message/esm_display_syntax_error_import.out
@@ -4,6 +4,7 @@ file:///*/test/message/esm_display_syntax_error_import.mjs:5
 SyntaxError: The requested module '../fixtures/es-module-loaders/module-named-exports.mjs' does not provide an export named 'notfound'
     at ModuleJob._instantiate (node:internal/modules/esm/module_job:*:*)
     at async ModuleJob.run (node:internal/modules/esm/module_job:*:*)
-    at async Loader.import (node:internal/modules/esm/loader:*:*)
-    at async Object.loadESM (node:internal/process/esm_loader:*:*)
+    at async Promise.all (index 0)
+    at async ESMLoader.import (node:internal/modules/esm/loader:*:*)
+    at async loadESM (node:internal/process/esm_loader:*:*)
     at async handleMainPromise (node:internal/modules/run_main:*:*)
diff --git a/test/message/esm_display_syntax_error_import_module.out b/test/message/esm_display_syntax_error_import_module.out
index 60a208d534af40..0ecb87a952e891 100644
--- a/test/message/esm_display_syntax_error_import_module.out
+++ b/test/message/esm_display_syntax_error_import_module.out
@@ -4,6 +4,7 @@ import { foo, notfound } from './module-named-exports.mjs';
 SyntaxError: The requested module './module-named-exports.mjs' does not provide an export named 'notfound'
     at ModuleJob._instantiate (node:internal/modules/esm/module_job:*:*)
     at async ModuleJob.run (node:internal/modules/esm/module_job:*:*)
-    at async Loader.import (node:internal/modules/esm/loader:*:*)
-    at async Object.loadESM (node:internal/process/esm_loader:*:*)
+    at async Promise.all (index 0)
+    at async ESMLoader.import (node:internal/modules/esm/loader:*:*)
+    at async loadESM (node:internal/process/esm_loader:*:*)
     at async handleMainPromise (node:internal/modules/run_main:*:*)
diff --git a/test/message/esm_display_syntax_error_module.out b/test/message/esm_display_syntax_error_module.out
index fc0912a96c0d26..26dbf480239b9c 100644
--- a/test/message/esm_display_syntax_error_module.out
+++ b/test/message/esm_display_syntax_error_module.out
@@ -3,4 +3,5 @@ await async () => 0;
 ^^^^^^^^^^^^^
 
 SyntaxError: Malformed arrow function parameter list
-    at Loader.moduleStrategy (node:internal/modules/esm/translators:*:*)
+    at ESMLoader.moduleStrategy (node:internal/modules/esm/translators:*:*)
+    at ESMLoader.moduleProvider (node:internal/modules/esm/loader:*:*)
diff --git a/test/message/esm_loader_not_found.out b/test/message/esm_loader_not_found.out
index 61b1623cdf176f..21d7ab3e44f205 100644
--- a/test/message/esm_loader_not_found.out
+++ b/test/message/esm_loader_not_found.out
@@ -7,12 +7,12 @@ Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'i-dont-exist' imported from *
     at new NodeError (node:internal/errors:*:*)
     at packageResolve (node:internal/modules/esm/resolve:*:*)
     at moduleResolve (node:internal/modules/esm/resolve:*:*)
-    at Loader.defaultResolve [as _resolve] (node:internal/modules/esm/resolve:*:*)
-    at Loader.resolve (node:internal/modules/esm/loader:*:*)
-    at Loader.getModuleJob (node:internal/modules/esm/loader:*:*)
-    at Loader.import (node:internal/modules/esm/loader:*:*)
-    at node:internal/process/esm_loader:*:*
+    at defaultResolve (node:internal/modules/esm/resolve:*:*)
+    at ESMLoader.resolve (node:internal/modules/esm/loader:*:*)
+    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:*:*)
+    at ESMLoader.import (node:internal/modules/esm/loader:*:*)
     at initializeLoader (node:internal/process/esm_loader:*:*)
-    at Object.loadESM (node:internal/process/esm_loader:*:*) {
+    at loadESM (node:internal/process/esm_loader:*:*)
+    at runMainESM (node:internal/modules/run_main:*:*) {
   code: 'ERR_MODULE_NOT_FOUND'
 }
diff --git a/test/message/esm_loader_not_found_cjs_hint_bare.out b/test/message/esm_loader_not_found_cjs_hint_bare.out
index aaeed40ed60013..4a255ebf0b6972 100644
--- a/test/message/esm_loader_not_found_cjs_hint_bare.out
+++ b/test/message/esm_loader_not_found_cjs_hint_bare.out
@@ -7,9 +7,9 @@ Did you mean to import some_module/obj.js?
     at new NodeError (node:internal/errors:*:*)
     at finalizeResolution (node:internal/modules/esm/resolve:*:*)
     at moduleResolve (node:internal/modules/esm/resolve:*:*)
-    at Loader.defaultResolve [as _resolve] (node:internal/modules/esm/resolve:*:*)
-    at Loader.resolve (node:internal/modules/esm/loader:*:*)
-    at Loader.getModuleJob (node:internal/modules/esm/loader:*:*)
+    at defaultResolve (node:internal/modules/esm/resolve:*:*)
+    at ESMLoader.resolve (node:internal/modules/esm/loader:*:*)
+    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:*:*)
     at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:*:*)
     at link (node:internal/modules/esm/module_job:*:*) {
   code: 'ERR_MODULE_NOT_FOUND'
diff --git a/test/message/esm_loader_not_found_cjs_hint_relative.out b/test/message/esm_loader_not_found_cjs_hint_relative.out
index 89b8d56133ce3a..817b4aa0724e8e 100644
--- a/test/message/esm_loader_not_found_cjs_hint_relative.out
+++ b/test/message/esm_loader_not_found_cjs_hint_relative.out
@@ -9,12 +9,12 @@ Did you mean to import ./test/common/fixtures.js?
     at new NodeError (node:internal/errors:*:*)
     at finalizeResolution (node:internal/modules/esm/resolve:*:*)
     at moduleResolve (node:internal/modules/esm/resolve:*:*)
-    at Loader.defaultResolve [as _resolve] (node:internal/modules/esm/resolve:*:*)
-    at Loader.resolve (node:internal/modules/esm/loader:*:*)
-    at Loader.getModuleJob (node:internal/modules/esm/loader:*:*)
-    at Loader.import (node:internal/modules/esm/loader:*:*)
-    at node:internal/process/esm_loader:*:*
+    at defaultResolve (node:internal/modules/esm/resolve:*:*)
+    at ESMLoader.resolve (node:internal/modules/esm/loader:*:*)
+    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:*:*)
+    at ESMLoader.import (node:internal/modules/esm/loader:*:*)
     at initializeLoader (node:internal/process/esm_loader:*:*)
-    at Object.loadESM (node:internal/process/esm_loader:*:*) {
+    at loadESM (node:internal/process/esm_loader:*:*)
+    at runMainESM (node:internal/modules/run_main:*:*) {
   code: 'ERR_MODULE_NOT_FOUND'
 }
diff --git a/test/message/esm_loader_syntax_error.out b/test/message/esm_loader_syntax_error.out
index de6014add667bc..fb8a2030828a9d 100644
--- a/test/message/esm_loader_syntax_error.out
+++ b/test/message/esm_loader_syntax_error.out
@@ -5,5 +5,6 @@ await async () => 0;
 ^^^^^^^^^^^^^
 
 SyntaxError: Malformed arrow function parameter list
-    at Loader.moduleStrategy (node:internal/modules/esm/translators:*:*)
+    at ESMLoader.moduleStrategy (node:internal/modules/esm/translators:*:*)
+    at ESMLoader.moduleProvider (node:internal/modules/esm/loader:*:*)
     at async link (node:internal/modules/esm/module_job:*:*)
diff --git a/test/message/test-esm-loader-obsolete-hooks.mjs b/test/message/test-esm-loader-obsolete-hooks.mjs
new file mode 100644
index 00000000000000..9a6a9c48057b40
--- /dev/null
+++ b/test/message/test-esm-loader-obsolete-hooks.mjs
@@ -0,0 +1,4 @@
+// Flags: --no-warnings --throw-deprecation --experimental-loader ./test/fixtures/es-module-loaders/hooks-obsolete.mjs
+/* eslint-disable node-core/require-common-first, node-core/required-modules */
+
+await import('whatever');
diff --git a/test/message/test-esm-loader-obsolete-hooks.out b/test/message/test-esm-loader-obsolete-hooks.out
new file mode 100644
index 00000000000000..5099c9c8d8610b
--- /dev/null
+++ b/test/message/test-esm-loader-obsolete-hooks.out
@@ -0,0 +1,10 @@
+node:internal/process/warning:*
+        throw warning;
+        ^
+
+DeprecationWarning: Obsolete loader hook(s) supplied and will be ignored: dynamicInstantiate, getFormat, getSource, transformSource
+    at Function.pluckHooks (node:internal/modules/esm/loader:*:*)
+    at ESMLoader.addCustomLoaders (node:internal/modules/esm/loader:*:*)
+    at initializeLoader (node:internal/process/esm_loader:*:*)
+    at async loadESM (node:internal/process/esm_loader:*:*)
+    at async handleMainPromise (node:internal/modules/run_main:*:*)
diff --git a/test/parallel/test-bootstrap-modules.js b/test/parallel/test-bootstrap-modules.js
index bb77c7201b21d2..b68a262103c7e8 100644
--- a/test/parallel/test-bootstrap-modules.js
+++ b/test/parallel/test-bootstrap-modules.js
@@ -72,10 +72,10 @@ const expectedModules = new Set([
   'NativeModule internal/modules/esm/get_format',
   'NativeModule internal/modules/esm/get_source',
   'NativeModule internal/modules/esm/loader',
+  'NativeModule internal/modules/esm/load',
   'NativeModule internal/modules/esm/module_job',
   'NativeModule internal/modules/esm/module_map',
   'NativeModule internal/modules/esm/resolve',
-  'NativeModule internal/modules/esm/transform_source',
   'NativeModule internal/modules/esm/translators',
   'NativeModule internal/process/esm_loader',
   'NativeModule internal/options',