esm: remove .js support

Refs: nodejs/modules#180

Author: MylesBorins

doc/api/esm.md

@@ -54,6 +54,10 @@ property:
 
 ## Notable differences between `import` and `require`
 
+### Only Support for .mjs
+
+ESM must have the `.mjs` extension
+
 ### No NODE_PATH
 
 `NODE_PATH` is not part of resolving `import` specifiers. Please use symlinks
@@ -145,7 +149,8 @@ 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:
+given module specifier
+ile URL:
 
 ```js
 const baseURL = new URL('file://');
@@ -174,7 +179,6 @@ module. This can be one of the following:
 | `format` | Description |
 | --- | --- |
 | `'esm'` | Load a standard JavaScript module |
-| `'cjs'` | Load a node-style CommonJS module |
 | `'dynamic'` | Use a [dynamic instantiate hook][] |
 
 For example, a dummy loader to load JavaScript restricted to browser resolution

lib/internal/modules/esm/default_resolve.js

@@ -45,8 +45,7 @@ function search(target, base) {
 
 const extensionFormatMap = {
   '__proto__': null,
-  '.mjs': 'esm',
-  '.js': 'cjs'
+  '.mjs': 'esm'
 };
 
 function resolve(specifier, parentURL) {

src/module_wrap.cc

@@ -42,7 +42,7 @@ using v8::TryCatch;
 using v8::Undefined;
 using v8::Value;
 
-static const char* const EXTENSIONS[] = {".mjs", ".js"};
+static const char* const EXTENSIONS[] = {".mjs"};
 
 ModuleWrap::ModuleWrap(Environment* env,
                        Local<Object> object,

test/common/index.mjs

@@ -1,6 +1,14 @@
 // Flags: --experimental-modules
 /* eslint-disable node-core/required-modules */
-import common from './index.js';
+
+import { createRequireFromPath } from 'module';
+
+function createRequire(url) {
+  return createRequireFromPath(url.replace('file://', ''));
+}
+
+const require = createRequire(import.meta.url);
+const common = require('./index.js');
 
 const {
   isMainThread,
@@ -97,5 +105,6 @@ export {
   getBufferSources,
   disableCrashOnUnhandledRejection,
   getTTYfd,
-  runWithInvalidFD
+  runWithInvalidFD,
+  createRequire
 };

test/es-module/test-esm-double-encoding.mjs

@@ -3,4 +3,4 @@ import '../common';
 
 // Assert we can import files with `%` in their pathname.
 
-import '../fixtures/es-modules/test-esm-double-encoding-native%2520.js';
+import '../fixtures/es-modules/test-esm-double-encoding-native%2520.mjs';

test/es-module/test-esm-dynamic-import.js

@@ -1,4 +1,5 @@
 // Flags: --experimental-modules
+
 'use strict';
 const common = require('../common');
 const assert = require('assert');

test/es-module/test-esm-error-cache.js

@@ -1,11 +1,11 @@
-'use strict';
-
 // Flags: --experimental-modules
 
+'use strict';
+
 require('../common');
 const assert = require('assert');
 
-const file = '../fixtures/syntax/bad_syntax.js';
+const file = '../fixtures/syntax/bad_syntax.mjs';
 
 let error;
 (async () => {

test/es-module/test-esm-require-cache.mjs

@@ -1,7 +1,11 @@
 // Flags: --experimental-modules
-import '../common';
-import '../fixtures/es-module-require-cache/preload.js';
-import '../fixtures/es-module-require-cache/counter.js';
+import { createRequire } from '../common';
 import assert from 'assert';
+//
+const require = createRequire(import.meta.url);
+
+require('../fixtures/es-module-require-cache/preload.js');
+require('../fixtures/es-module-require-cache/counter.js');
+
 assert.strictEqual(global.counter, 1);
 delete global.counter;

test/es-module/test-esm-shared-loader-dep.mjs

@@ -1,7 +1,9 @@
 // Flags: --experimental-modules --loader ./test/fixtures/es-module-loaders/loader-shared-dep.mjs
-import '../common';
+import { createRequire } from '../common';
 import assert from 'assert';
 import '../fixtures/es-modules/test-esm-ok.mjs';
-import dep from '../fixtures/es-module-loaders/loader-dep.js';
+
+const require = createRequire(import.meta.url);
+const dep = require('../fixtures/es-module-loaders/loader-dep.js');
 
 assert.strictEqual(dep.format, 'esm');

test/es-module/test-esm-snapshot.mjs

@@ -1,6 +1,10 @@
-import dep from './loader-dep.js';
 import assert from 'assert';
 
+import {createRequire} from '../../common';
+
+const require = createRequire(import.meta.url);
+const dep = require('./loader-dep.js');
+
 export function resolve(specifier, base, defaultResolve) {
   assert.strictEqual(dep.format, 'esm');
   return defaultResolve(specifier, base);

test/fixtures/es-module-loaders/loader-shared-dep.mjs

@@ -1,4 +1,8 @@
-import dep from './loader-dep.js';
+import {createRequire} from '../../common';
+
+const require = createRequire(import.meta.url);
+const dep = require('./loader-dep.js');
+
 export function resolve (specifier, base, defaultResolve) {
   return {
     url: defaultResolve(specifier, base).url,

test/fixtures/es-module-loaders/loader-with-dep.mjs

@@ -0,0 +1 @@
+export default 'main';

test/fixtures/es-modules/esm-snapshot-mutator.js

@@ -1,3 +1,3 @@
 {
-  "main": "main.js"
+  "main": "main.mjs"
 }

test/fixtures/es-modules/esm-snapshot.js

@@ -3,4 +3,4 @@
 // Trivial test to assert we can load files with `%` in their pathname.
 // Imported by `test-esm-double-encoding.mjs`.
 
-module.exports = 42;
+export default 42;

test/fixtures/es-modules/pjson-main/main.js

@@ -0,0 +1 @@
+var foo bar;