Minimal kernel

.eslintrc.js

@@ -36,7 +36,6 @@ module.exports = {
       files: [
         'doc/api/esm.md',
         '*.mjs',
-        'test/es-module/test-esm-example-loader.js',
       ],
       parserOptions: { sourceType: 'module' },
     },

doc/api/cli.md

@@ -97,13 +97,6 @@ added: v10.0.0
 
 Enable experimental top-level `await` keyword support in REPL.
 
-### `--experimental-vm-modules`
-<!-- YAML
-added: v9.6.0
--->
-
-Enable experimental ES Module support in the `vm` module.
-
 ### `--experimental-worker`
 <!-- YAML
 added: v10.5.0
@@ -155,13 +148,6 @@ V8 inspector integration allows tools such as Chrome DevTools and IDEs to debug
 and profile Node.js instances. The tools attach to Node.js instances via a
 tcp port and communicate using the [Chrome DevTools Protocol][].
 
-### `--loader=file`
-<!--
-added: v9.0.0
--->
-
-Specify the `file` of the custom [experimental ECMAScript Module][] loader.
-
 ### `--napi-modules`
 <!-- YAML
 added: v7.10.0
@@ -554,14 +540,12 @@ Node options that are allowed are:
 - `--enable-fips`
 - `--experimental-modules`
 - `--experimental-repl-await`
-- `--experimental-vm-modules`
 - `--experimental-worker`
 - `--force-fips`
 - `--icu-data-dir`
 - `--inspect`
 - `--inspect-brk`
 - `--inspect-port`
-- `--loader`
 - `--napi-modules`
 - `--no-deprecation`
 - `--no-force-async-hooks-checks`
@@ -739,5 +723,4 @@ greater than `4` (its current default value). For more information, see the
 [V8 JavaScript code coverage]: https://v8project.blogspot.com/2017/12/javascript-code-coverage.html
 [debugger]: debugger.html
 [emit_warning]: process.html#process_process_emitwarning_warning_type_code_ctor
-[experimental ECMAScript Module]: esm.html#esm_loader_hooks
 [libuv threadpool documentation]: http://docs.libuv.org/en/latest/threadpool.html

doc/api/esm.md

@@ -8,10 +8,11 @@
 <!--name=esm-->
 
 Node.js contains support for ES Modules based upon the
-[Node.js EP for ES Modules][].
+[Node.js EP for ES Modules][] and the [ESM Minimal Kernel][].
 
-Not all features of the EP are complete and will be landing as both VM support
-and implementation is ready. Error messages are still being polished.
+The minimal feature set is designed to be compatible with all potential
+future implementations. Expect major changes in the implementation including
+interoperability support, specifier resolution, and default behavior.
 
 ## Enabling
 
@@ -54,6 +55,18 @@ property:
 
 ## Notable differences between `import` and `require`
 
+### Only Support for .mjs
+
+ESM must have the `.mjs` extension.
+
+### Mandatory file extensions
+
+You must provide a file extension when using the `import` keyword.
+
+### No importing directories
+
+There is no support for importing directories.
+
 ### No NODE_PATH
 
 `NODE_PATH` is not part of resolving `import` specifiers. Please use symlinks
@@ -78,31 +91,32 @@ Modules will be loaded multiple times if the `import` specifier used to resolve
 them have a different query or fragment.
 
 ```js
-import './foo?query=1'; // loads ./foo with query of "?query=1"
-import './foo?query=2'; // loads ./foo with query of "?query=2"
+import './foo.mjs?query=1'; // loads ./foo.mjs with query of "?query=1"
+import './foo.mjs?query=2'; // loads ./foo.mjs with query of "?query=2"
 ```
 
 For now, only modules using the `file:` protocol can be loaded.
 
-## Interop with existing modules
+## CommonJS, JSON, and Native Modules
 
-All CommonJS, JSON, and C++ modules can be used with `import`.
+CommonJS, JSON, and Native modules can be used with [`module.createRequireFromPath()`][].
 
-Modules loaded this way will only be loaded once, even if their query
-or fragment string differs between `import` statements.
+```js
+// cjs.js
+module.exports = 'cjs';
 
-When loaded via `import` these modules will provide a single `default` export
-representing the value of `module.exports` at the time they finished evaluating.
+// esm.mjs
+import { createRequireFromPath as createRequire } from 'module';
+import { fileURLToPath as fromPath } from 'url';
 
-```js
-// foo.js
-module.exports = { one: 1 };
+const require = createRequire(fromPath(import.meta.url));
 
-// bar.js
-import foo from './foo.js';
-foo.one === 1; // true
+const cjs = require('./cjs');
+cjs === 'cjs'; // true
 ```
 
+## Builtin modules
+
 Builtin modules will provide named exports of their public API, as well as a
 default export which can be used for, among other things, modifying the named
 exports. Named exports of builtin modules are updated when the corresponding
@@ -132,127 +146,6 @@ fs.readFileSync = () => Buffer.from('Hello, ESM');
 fs.readFileSync === readFileSync;
 ```
 
-## Loader hooks
-
-<!-- type=misc -->
-
-To customize the default module resolution, loader hooks can optionally be
-provided via a `--loader ./loader-name.mjs` argument to Node.js.
-
-When hooks are used they only apply to ES module loading and not to any
-CommonJS modules loaded.
-
-### Resolve hook
-
-The resolve hook returns the resolved file URL and module format for a
-given module specifier and parent file URL:
-
-```js
-const baseURL = new URL('file://');
-baseURL.pathname = `${process.cwd()}/`;
-
-export async function resolve(specifier,
-                              parentModuleURL = baseURL,
-                              defaultResolver) {
-  return {
-    url: new URL(specifier, parentModuleURL).href,
-    format: 'esm'
-  };
-}
-```
-
-The `parentModuleURL` is provided as `undefined` when performing main Node.js
-load itself.
-
-The default Node.js ES module resolution function is provided as a third
-argument to the resolver for easy compatibility workflows.
-
-In addition to returning the resolved file URL value, the resolve hook also
-returns a `format` property specifying the module format of the resolved
-module. This can be one of the following:
-
-| `format` | Description |
-| --- | --- |
-| `'esm'` | Load a standard JavaScript module |
-| `'cjs'` | Load a node-style CommonJS module |
-| `'builtin'` | Load a node builtin CommonJS module |
-| `'json'` | Load a JSON file |
-| `'addon'` | Load a [C++ Addon][addons] |
-| `'dynamic'` | Use a [dynamic instantiate hook][] |
-
-For example, a dummy loader to load JavaScript restricted to browser resolution
-rules with only JS file extension and Node.js builtin modules support could
-be written:
-
-```js
-import path from 'path';
-import process from 'process';
-import Module from 'module';
-
-const builtins = Module.builtinModules;
-const JS_EXTENSIONS = new Set(['.js', '.mjs']);
-
-const baseURL = new URL('file://');
-baseURL.pathname = `${process.cwd()}/`;
-
-export function resolve(specifier, parentModuleURL = baseURL, defaultResolve) {
-  if (builtins.includes(specifier)) {
-    return {
-      url: specifier,
-      format: 'builtin'
-    };
-  }
-  if (/^\.{0,2}[/]/.test(specifier) !== true && !specifier.startsWith('file:')) {
-    // For node_modules support:
-    // return defaultResolve(specifier, parentModuleURL);
-    throw new Error(
-      `imports must begin with '/', './', or '../'; '${specifier}' does not`);
-  }
-  const resolved = new URL(specifier, parentModuleURL);
-  const ext = path.extname(resolved.pathname);
-  if (!JS_EXTENSIONS.has(ext)) {
-    throw new Error(
-      `Cannot load file with non-JavaScript file extension ${ext}.`);
-  }
-  return {
-    url: resolved.href,
-    format: 'esm'
-  };
-}
-```
-
-With this loader, running:
-
-```console
-NODE_OPTIONS='--experimental-modules --loader ./custom-loader.mjs' node x.js
-```
-
-would load the module `x.js` as an ES module with relative resolution support
-(with `node_modules` loading skipped in this example).
-
-### Dynamic instantiate hook
-
-To create a custom dynamic module that doesn't correspond to one of the
-existing `format` interpretations, the `dynamicInstantiate` hook can be used.
-This hook is called only for modules that return `format: 'dynamic'` from
-the `resolve` hook.
-
-```js
-export async function dynamicInstantiate(url) {
-  return {
-    exports: ['customExportName'],
-    execute: (exports) => {
-      // get and set functions provided for pre-allocated export names
-      exports.customExportName.set('value');
-    }
-  };
-}
-```
-
-With the list of module exports provided upfront, the `execute` function will
-then be called at the exact point of module evaluation order for that module
-in the import tree.
-
 [Node.js EP for ES Modules]: https://github.com/nodejs/node-eps/blob/master/002-es-modules.md
-[addons]: addons.html
-[dynamic instantiate hook]: #esm_dynamic_instantiate_hook
+[`module.createRequireFromPath()`]: modules.html#modules_module_createrequirefrompath_filename
+[ESM Minimal Kernel]: https://github.com/nodejs/modules/blob/master/doc/plan-for-new-modules-implementation.md