Convert own source to ES modules

.eslintrc.json

@@ -11,11 +11,13 @@
     "eslint:all",
     "prettier",
 
-    "plugin:n/recommended"
+    // Need to be specific, because this config is one level above the package.jsons that have type:module
+    "plugin:n/recommended-module"
   ],
   "plugins": ["import"],
   "parserOptions": {
-    "ecmaVersion": 2022
+    "ecmaVersion": 2022,
+    "sourceType": "module"
   },
   "env": {
     "es2021": true,
@@ -36,6 +38,7 @@
     "no-ternary": "off",
     "no-undefined": "off",
     "one-var": "off",
+    "sort-imports": "off", // using import/order instead
     "sort-keys": "off",
     "strict": "off",
 
@@ -64,13 +67,11 @@
       { "blankLine": "always", "prev": "*", "next": ["cjs-export"] },
 
       { "blankLine": "always", "prev": "*", "next": "block-like" },
-      { "blankLine": "always", "prev": "block-like", "next": "*" },
-
-      { "blankLine": "always", "prev": "cjs-import", "next": "*" },
-      { "blankLine": "any", "prev": "cjs-import", "next": "cjs-import" }
+      { "blankLine": "always", "prev": "block-like", "next": "*" }
     ],
 
-    // eslint-plugin-import - Selection from the ones that are compatible with CommonJS
+    // eslint-plugin-import - selection (not comprehensive)
+    "import/newline-after-import": "error",
     "import/no-extraneous-dependencies": "error",
     "import/order": ["error", { "newlines-between": "never" }]
   }

CONTRIBUTING.md

@@ -19,7 +19,7 @@ Different versions may work, but majorly newer/older tooling versions are likely
 - Verify there are no uncommitted changes
 - `npm run ci` in root
 - `npm run lint` in the example project, check number of errors and presence of new expected ones
-- `../check-es-compat/bin/cli.mjs .` in the example project, it should produce the same errors
+- `../check-es-compat/bin/cli.js .` in the example project, it should produce the same errors
 - `lerna clean` then `lerna bootstrap`, verify no changes were introduced (e.g. to `package-lock.json`)
 
 ## Releasing

package.json

@@ -3,8 +3,8 @@
   "private": true,
   "scripts": {
     "check": "npm-run-all --parallel check:*",
-    "check:lint": "eslint --no-eslintrc --config=.eslintrc.json **/*.{js,mjs}",
-    "check:prettier": "prettier --check **/*.{js,json,md,mjs}",
+    "check:lint": "eslint --no-eslintrc --config=.eslintrc.json **/*.js",
+    "check:prettier": "prettier --check **/*.{js,json,md}",
     "ci": "npm-run-all check test",
     "postinstall": "lerna bootstrap",
     "test": "lerna run test"

packages/check-es-compat/package.json

@@ -26,8 +26,9 @@
   },
   "license": "MIT",
   "author": "Robat Williams",
+  "type": "module",
   "bin": {
-    "check-es-compat": "bin/cli.mjs"
+    "check-es-compat": "bin/cli.js"
   },
   "dependencies": {
     "eslint": "^8.56.0",

packages/eslint-plugin-ecmascript-compat/lib/compareVersions.js

@@ -1,4 +1,4 @@
-module.exports = function compareVersions(a, b) {
+export default function compareVersions(a, b) {
   const aParts = a.split('.').map(Number);
   const bParts = b.split('.').map(Number);
 
@@ -12,4 +12,4 @@ module.exports = function compareVersions(a, b) {
   }
 
   return 0;
-};
+}

packages/eslint-plugin-ecmascript-compat/lib/compareVersions.test.js

@@ -1,6 +1,6 @@
-const assert = require('node:assert');
-const { test } = require('node:test');
-const compareVersions = require('./compareVersions');
+import assert from 'node:assert';
+import { test } from 'node:test';
+import compareVersions from './compareVersions.js';
 
 test('equal', () => {
   assert.strictEqual(compareVersions('1.2.3', '1.2.3'), 0);

packages/eslint-plugin-ecmascript-compat/lib/compatibility.js

@@ -1,7 +1,7 @@
 /* eslint-disable camelcase, no-underscore-dangle */
-const compareVersions = require('./compareVersions');
+import compareVersions from './compareVersions.js';
 
-function unsupportedFeatures(features, targets) {
+export function unsupportedFeatures(features, targets) {
   return features.filter((feature) => !isFeatureSupportedByTargets(feature, targets));
 }
 
@@ -54,5 +54,3 @@ function interpretSupport(versionAdded) {
     isVersionUnknown: versionAdded === true,
   };
 }
-
-module.exports = { unsupportedFeatures };

packages/eslint-plugin-ecmascript-compat/lib/compatibility.test.js

@@ -1,8 +1,8 @@
 /* eslint-disable camelcase */
-const assert = require('node:assert');
-const { it } = require('node:test');
-const { unsupportedFeatures } = require('./compatibility');
-const features = require('./features');
+import assert from 'node:assert';
+import { it } from 'node:test';
+import { unsupportedFeatures } from './compatibility.js';
+import features from './features/index.js';
 
 it('supports feature in version introduced', () => {
   const feature = {

packages/eslint-plugin-ecmascript-compat/lib/delegation.js

@@ -1,4 +1,4 @@
-function createDelegatee(config, rootContext) {
+export function createDelegatee(config, rootContext) {
   const { definition, options } = config;
 
   if (!definition) {
@@ -44,7 +44,7 @@ function createDelegatee(config, rootContext) {
   return definition.create(context);
 }
 
-function delegatingVisitor(delegatees) {
+export function delegatingVisitor(delegatees) {
   const delegator = {};
 
   delegatees.forEach((visitor) => {
@@ -63,5 +63,3 @@ function delegatingVisitor(delegatees) {
 
   return delegator;
 }
-
-module.exports = { createDelegatee, delegatingVisitor };

packages/eslint-plugin-ecmascript-compat/lib/delegation.test.js

@@ -1,5 +1,5 @@
-const eslint = require('eslint');
-const { createDelegatee, delegatingVisitor } = require('./delegation');
+import eslint from 'eslint';
+import { createDelegatee, delegatingVisitor } from './delegation.js';
 
 const ruleTester = new eslint.RuleTester();
 

packages/eslint-plugin-ecmascript-compat/lib/features/es2016.js

@@ -1,11 +1,12 @@
-const eslint = require('eslint');
-const esPlugin = require('eslint-plugin-es-x');
-const compatData = require('@mdn/browser-compat-data');
-const { noRestrictedSyntaxPrototypeMethod } = require('./ruleOptionsUtil');
+import eslint from 'eslint';
+import esPlugin from 'eslint-plugin-es-x';
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import { noRestrictedSyntaxPrototypeMethod } from './ruleOptionsUtil.js';
 
 const coreRules = new eslint.Linter().getRules();
 
-module.exports = [
+export default [
   {
     ruleConfig: {
       definition: coreRules.get('no-restricted-syntax'),

packages/eslint-plugin-ecmascript-compat/lib/features/es2016.test.js

@@ -1,4 +1,5 @@
-const { RuleTester } = require('eslint');
+import { RuleTester } from 'eslint';
+import rule from '../rule.js';
 
 // Browser that doesn't support any features of this version - see es-versions.md
 process.env.BROWSERSLIST = 'Chrome >= 46';
@@ -9,7 +10,7 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.run('compat', require('../rule'), {
+ruleTester.run('compat', rule, {
   valid: [
     {
       code: 'foo.includes();',

packages/eslint-plugin-ecmascript-compat/lib/features/es2017.js

@@ -1,11 +1,12 @@
-const eslint = require('eslint');
-const esPlugin = require('eslint-plugin-es-x');
-const compatData = require('@mdn/browser-compat-data');
-const { noRestrictedSyntaxPrototypeMethod } = require('./ruleOptionsUtil');
+import eslint from 'eslint';
+import esPlugin from 'eslint-plugin-es-x';
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import { noRestrictedSyntaxPrototypeMethod } from './ruleOptionsUtil.js';
 
 const coreRules = new eslint.Linter().getRules();
 
-module.exports = [
+export default [
   {
     ruleConfig: { definition: esPlugin.rules['no-async-functions'] },
     compatFeatures: [

packages/eslint-plugin-ecmascript-compat/lib/features/es2017.test.js

@@ -1,4 +1,5 @@
-const { RuleTester } = require('eslint');
+import { RuleTester } from 'eslint';
+import rule from '../rule.js';
 
 // Browser that doesn't support any features of this version - see es-versions.md
 process.env.BROWSERSLIST = 'Chrome >= 53';
@@ -16,7 +17,7 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.run('compat', require('../rule'), {
+ruleTester.run('compat', rule, {
   valid: [
     {
       code: 'Object.getOwnPropertyDescriptors();',

packages/eslint-plugin-ecmascript-compat/lib/features/es2018.js

@@ -1,11 +1,12 @@
-const eslint = require('eslint');
-const esPlugin = require('eslint-plugin-es-x');
-const compatData = require('@mdn/browser-compat-data');
-const { noRestrictedSyntaxPrototypeMethod } = require('./ruleOptionsUtil');
+import eslint from 'eslint';
+import esPlugin from 'eslint-plugin-es-x';
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import { noRestrictedSyntaxPrototypeMethod } from './ruleOptionsUtil.js';
 
 const coreRules = new eslint.Linter().getRules();
 
-module.exports = [
+export default [
   {
     ruleConfig: { definition: esPlugin.rules['no-async-iteration'] },
     compatFeatures: [

packages/eslint-plugin-ecmascript-compat/lib/features/es2018.test.js

@@ -1,4 +1,5 @@
-const { RuleTester } = require('eslint');
+import { RuleTester } from 'eslint';
+import rule from '../rule.js';
 
 // Browser that doesn't support any features of this version - see es-versions.md
 process.env.BROWSERSLIST = 'Chrome >= 59';
@@ -9,7 +10,7 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.run('compat', require('../rule'), {
+ruleTester.run('compat', rule, {
   valid: [
     {
       code: 'foo.finally();',

packages/eslint-plugin-ecmascript-compat/lib/features/es2019.js

@@ -1,11 +1,12 @@
-const eslint = require('eslint');
-const esPlugin = require('eslint-plugin-es-x');
-const compatData = require('@mdn/browser-compat-data');
-const { noRestrictedSyntaxPrototypeMethod } = require('./ruleOptionsUtil');
+import eslint from 'eslint';
+import esPlugin from 'eslint-plugin-es-x';
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import { noRestrictedSyntaxPrototypeMethod } from './ruleOptionsUtil.js';
 
 const coreRules = new eslint.Linter().getRules();
 
-module.exports = [
+export default [
   {
     ruleConfig: {
       definition: coreRules.get('no-restricted-syntax'),

packages/eslint-plugin-ecmascript-compat/lib/features/es2019.test.js

@@ -1,4 +1,5 @@
-const { RuleTester } = require('eslint');
+import { RuleTester } from 'eslint';
+import rule from '../rule.js';
 
 // Browser that doesn't support any features of this version - see es-versions.md
 process.env.BROWSERSLIST = 'Chrome >= 65';
@@ -9,7 +10,7 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.run('compat', require('../rule'), {
+ruleTester.run('compat', rule, {
   valid: [
     {
       code: 'const flat = residentialAddress.flat;',

packages/eslint-plugin-ecmascript-compat/lib/features/es2020.js

@@ -1,11 +1,12 @@
-const eslint = require('eslint');
-const esPlugin = require('eslint-plugin-es-x');
-const compatData = require('@mdn/browser-compat-data');
-const { noRestrictedSyntaxPrototypeMethod } = require('./ruleOptionsUtil');
+import eslint from 'eslint';
+import esPlugin from 'eslint-plugin-es-x';
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import { noRestrictedSyntaxPrototypeMethod } from './ruleOptionsUtil.js';
 
 const coreRules = new eslint.Linter().getRules();
 
-module.exports = [
+export default [
   {
     ruleConfig: {
       definition: coreRules.get('no-restricted-properties'),

packages/eslint-plugin-ecmascript-compat/lib/features/es2020.test.js

@@ -1,4 +1,5 @@
-const { RuleTester } = require('eslint');
+import { RuleTester } from 'eslint';
+import rule from '../rule.js';
 
 // Browser that doesn't support any features of this version - see es-versions.md
 process.env.BROWSERSLIST = 'Chrome >= 62';
@@ -20,7 +21,7 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.run('compat', require('../rule'), {
+ruleTester.run('compat', rule, {
   valid: [
     {
       code: 'globalThis.foo;',

packages/eslint-plugin-ecmascript-compat/lib/features/es2021.js

@@ -1,11 +1,12 @@
-const eslint = require('eslint');
-const compatData = require('@mdn/browser-compat-data');
-const esPlugin = require('eslint-plugin-es-x');
-const { noRestrictedSyntaxPrototypeMethod } = require('./ruleOptionsUtil');
+import eslint from 'eslint';
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import esPlugin from 'eslint-plugin-es-x';
+import { noRestrictedSyntaxPrototypeMethod } from './ruleOptionsUtil.js';
 
 const coreRules = new eslint.Linter().getRules();
 
-module.exports = [
+export default [
   {
     ruleConfig: {
       definition: coreRules.get('no-restricted-syntax'),

packages/eslint-plugin-ecmascript-compat/lib/features/es2021.test.js

@@ -1,4 +1,5 @@
-const { RuleTester } = require('eslint');
+import { RuleTester } from 'eslint';
+import rule from '../rule.js';
 
 // Browser that doesn't support any features of this version - see es-versions.md
 process.env.BROWSERSLIST = 'Chrome >= 74';
@@ -16,7 +17,7 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.run('compat', require('../rule'), {
+ruleTester.run('compat', rule, {
   valid: [
     {
       code: '"A dog".replaceAll("dog", "monkey");',

packages/eslint-plugin-ecmascript-compat/lib/features/es2022.js

@@ -1,7 +1,8 @@
-const compatData = require('@mdn/browser-compat-data');
-const esPlugin = require('eslint-plugin-es-x');
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import esPlugin from 'eslint-plugin-es-x';
 
-module.exports = [
+export default [
   {
     ruleConfig: {
       definition: esPlugin.rules['no-array-string-prototype-at'],

packages/eslint-plugin-ecmascript-compat/lib/features/es2022.test.js

@@ -1,4 +1,5 @@
-const { RuleTester } = require('eslint');
+import { RuleTester } from 'eslint';
+import rule from '../rule.js';
 
 // Browser that doesn't support any features of this version - see es-versions.md
 process.env.BROWSERSLIST = 'Chrome >= 71';
@@ -10,7 +11,7 @@ const ruleTester = new RuleTester({
   },
 });
 
-ruleTester.run('compat', require('../rule'), {
+ruleTester.run('compat', rule, {
   valid: [
     {
       code: '[].at(1);',

packages/eslint-plugin-ecmascript-compat/lib/features/es2023.js

@@ -1,7 +1,8 @@
-const compatData = require('@mdn/browser-compat-data');
-const esPlugin = require('eslint-plugin-es-x');
+// Import assertions aren't yet stage 4 so aren't supported by ESLint
+import compatData from '@mdn/browser-compat-data/forLegacyNode';
+import esPlugin from 'eslint-plugin-es-x';
 
-module.exports = [
+export default [
   {
     ruleConfig: {
       definition: esPlugin.rules['no-array-prototype-findlast-findlastindex'],