Move to ESM and flat config

Fixes #2278

Author: sindresorhus

.eslint-doc-generatorrc.js

@@ -2,20 +2,24 @@
 
 /** @type {import('eslint-doc-generator').GenerateOptions} */
 const config = {
-  ignoreConfig: ['all', 'flat/all', 'flat/recommended'],
-  ignoreDeprecatedRules: true,
-  ruleDocTitleFormat: 'desc',
-  ruleListColumns: [
-    'name',
-    'description',
-    'configsError',
-    // Omit `configsOff` since we don't intend to convey meaning by setting rules to `off` in the `recommended` config.
-    'configsWarn',
-    'fixable',
-    'hasSuggestions',
-    'requiresTypeChecking',
-  ],
-  urlConfigs: 'https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs-eslintconfigjs',
+	ignoreConfig: [
+		'all',
+		'flat/all',
+		'flat/recommended',
+	],
+	ignoreDeprecatedRules: true,
+	ruleDocTitleFormat: 'desc',
+	ruleListColumns: [
+		'name',
+		'description',
+		'configsError',
+		// Omit `configsOff` since we don't intend to convey meaning by setting rules to `off` in the `recommended` config.
+		'configsWarn',
+		'fixable',
+		'hasSuggestions',
+		'requiresTypeChecking',
+	],
+	urlConfigs: 'https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs-eslintconfigjs',
 };
 
-module.exports = config;
+export default config;

.github/workflows/main.yml

@@ -15,8 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         node-version:
-          - 20
-          - 18
+          - 23
         os:
           - ubuntu-latest
           - windows-latest
@@ -43,7 +42,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           # Locked due to the difference of `zlib.gzipSync()` between Node.js versions
-          node-version: 20
+          node-version: 23
       - run: npm install
       - run: npm run lint
       - run: npx del-cli test/snapshots --verbose
@@ -62,6 +61,8 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
+        with:
+          node-version: 23
       - run: npm install
       - run: npm run run-rules-on-codebase
   integration:
@@ -85,5 +86,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
+        with:
+          node-version: 23
       - run: npm install
       - run: npm run integration -- --group ${{ matrix.group }}

configs/flat-config-base.js

@@ -1,8 +1,9 @@
-'use strict';
-const globals = require('globals');
+import globals from 'globals';
 
-module.exports = {
+const config = {
 	languageOptions: {
 		globals: globals.builtin,
 	},
 };
+
+export default config;

configs/legacy-config-base.js

@@ -13,7 +13,7 @@ Use the [`astexplorer` site](https://astexplorer.net) with the `espree` parser a
 ## Steps
 
 - Run `npm run create-rule` to create files for the new rule.
-- Open “test/{RULE_ID}.mjs” and [write some tests](./write-tests.md) before implementing the rule.
+- Open “test/{RULE_ID}.js” and [write some tests](./write-tests.md) before implementing the rule.
 - Open “rules/{RULE_ID}.js” and implement the rule logic.
 - Add the correct [`meta.type`](https://eslint.org/docs/developer-guide/working-with-rules#rule-basics) to the rule.
 - Open “docs/rules/{RULE_ID}.js” and write some documentation.

docs/new-rule.md

@@ -12,13 +12,15 @@ Passing functions to iterator methods can cause issues when the function is chan
 Suppose you have a `unicorn` module:
 
 ```js
-module.exports = x => x + 1;
+const unicorn = x => x + 1;
+
+export default unicorn;
 ```
 
 You can then use it like this:
 
 ```js
-const unicorn = require('unicorn');
+import unicorn from 'unicorn';
 
 [1, 2, 3].map(unicorn);
 //=> [2, 3, 4]
@@ -27,13 +29,15 @@ const unicorn = require('unicorn');
 The `unicorn` module now does a minor version that adds another argument:
 
 ```js
-module.exports = (x, y) => x + (y ? y : 1);
+const unicorn = (x, y) => x + (y ? y : 1);
+
+export default unicorn;
 ```
 
 Your code will now return something different and probably break for users because it is now passing the index of the item as second argument.
 
 ```js
-const unicorn = require('unicorn');
+import unicorn from 'unicorn';
 
 [1, 2, 3].map(unicorn);
 //=> [2, 3, 5]
@@ -42,7 +46,7 @@ const unicorn = require('unicorn');
 This rule helps safely call the function with the expected number of parameters:
 
 ```js
-const unicorn = require('unicorn');
+import unicorn from 'unicorn';
 
 [1, 2, 3].map(x => unicorn(x));
 //=> [2, 3, 4]

docs/rules/no-array-callback-reference.md

@@ -26,7 +26,7 @@ package.json
 ```
 
 ```js
-const assign = require('object-assign');
+import assign from 'object-assign';
 ```
 
 ## Pass
@@ -42,7 +42,7 @@ package.json
 ```
 
 ```js
-const assign = require('object-assign'); // Passes as Object.assign is not supported
+import assign from 'object-assign'; // Passes as Object.assign is not supported
 ```
 
 ## Options

docs/rules/no-unnecessary-polyfills.md

@@ -69,7 +69,8 @@ This option lets you specify a list of packages that disable the rule when impor
 With `koa`, this would still pass:
 
 ```js
-const Koa = require('koa');
+import Koa from 'koa';
+
 const app = new Koa();
 
 app.onerror = () => {};

docs/rules/prefer-add-event-listener.md

@@ -9,12 +9,6 @@
 
 When importing builtin modules, it's better to use the [`node:` protocol](https://nodejs.org/api/esm.html#node-imports) as it makes it perfectly clear that the package is a Node.js builtin module.
 
-Note that Node.js support for this feature began in:
-
-> v16.0.0, v14.18.0 (`require()`)
->
-> v14.13.1, v12.20.0 (`import`)
-
 ## Fail
 
 ```js
@@ -29,14 +23,6 @@ export {strict as default} from 'assert';
 import fs from 'fs/promises';
 ```
 
-```js
-const fs = require('fs');
-```
-
-```js
-const fs = require('fs/promises');
-```
-
 ## Pass
 
 ```js
@@ -58,7 +44,3 @@ import _ from 'lodash';
 ```js
 import fs from './fs.js';
 ```
-
-```js
-const fs = require('node:fs/promises');
-```

docs/rules/prefer-node-protocol.md

@@ -188,10 +188,6 @@ import tempWrite from 'temp-write';
 import * as err from 'err';
 ```
 
-```js
-const err = require('err');
-```
-
 ### checkShorthandImports
 
 Type: `'internal'` | `boolean`\
@@ -222,10 +218,6 @@ Pass `"checkShorthandProperties": true` to check variables declared as shorthand
 
 With this set to `true` the following code will be reported.
 
-```js
-const {prop} = require('ramda');
-```
-
 ```js
 const {err} = foo;
 ```

docs/rules/prevent-abbreviations.md

@@ -5,7 +5,7 @@ Tests are in the `/test` directory.
 A rule test file should look like this:
 
 ```js
-import {getTester} from './utils/test.mjs';
+import {getTester} from './utils/test.js';
 
 const {test} = getTester(import.meta);
 
@@ -21,12 +21,12 @@ test.snapshot({
 
 ## `test.snapshot()`
 
-This runs [`SnapshotRuleTester`](../test/utils/snapshot-rule-tester.mjs), which auto-generates the snapshot for test results, including error messages, error locations, autofix result, and suggestions. All you have to do is check the snapshot and make sure the results are expected before committing.
+This runs [`SnapshotRuleTester`](../test/utils/snapshot-rule-tester.js), which auto-generates the snapshot for test results, including error messages, error locations, autofix result, and suggestions. All you have to do is check the snapshot and make sure the results are expected before committing.
 
 It's recommended to use this approach as it simplifies test writing.
 
 ```js
-import {getTester} from './utils/test.mjs';
+import {getTester} from './utils/test.js';
 
 const {test} = getTester(import.meta);
 
@@ -45,13 +45,13 @@ test.snapshot({
 We use [`AVA`](https://github.com/avajs/ava) to run tests. To focus on a specific rule test, you can:
 
 ```console
-npx ava test/rule-name.mjs
+npx ava test/rule-name.js
 ```
 
 To update snapshots, run the command above with [`--update-snapshots` or `-u`](https://github.com/avajs/ava/blob/main/docs/05-command-line.md#cli).
 
 ```console
-npx ava test/rule-name.mjs -u
+npx ava test/rule-name.js -u
 ```
 
 ## Focus on one test case
@@ -91,7 +91,7 @@ test.snapshot({
 This runs [`eslint-ava-rule-tester`](https://github.com/jfmengels/eslint-ava-rule-tester):
 
 ```js
-import {getTester} from './utils/test.mjs';
+import {getTester} from './utils/test.js';
 
 const {test} = getTester(import.meta);
 
@@ -141,10 +141,10 @@ test.snapshot({
 
 ## `parsers`
 
-[`utils/test.mjs`](../test/utils/test.mjs) also exposes a `parsers` object, which can be used in `testerOptions` or `parser` for a single test case.
+[`utils/test.js`](../test/utils/test.js) also exposes a `parsers` object, which can be used in `testerOptions` or `parser` for a single test case.
 
 ```js
-import {getTester, parsers} from './utils/test.mjs';
+import {getTester, parsers} from './utils/test.js';
 
 const {test} = getTester(import.meta);
 
@@ -158,7 +158,7 @@ test.snapshot({
 ```
 
 ```js
-import {getTester, parsers} from './utils/test.mjs';
+import {getTester, parsers} from './utils/test.js';
 
 const {test} = getTester(import.meta);
 
@@ -175,4 +175,4 @@ test.snapshot({
 
 Why use `parser: parsers.babel` instead of `parser: '@babel/eslint-parser'`?
 
-Using `parsers.babel` will make the `parserOptions` merge with useful default options. See [`parser.mjs`](../test/utils/parsers.mjs) for details.
+Using `parsers.babel` will make the `parserOptions` merge with useful default options. See [`parser.js`](../test/utils/parsers.js) for details.

docs/write-tests.md

@@ -0,0 +1,68 @@
+import globals from 'globals';
+import xo from 'eslint-config-xo';
+import eslintPlugin from 'eslint-plugin-eslint-plugin';
+import internal from './scripts/internal-rules/index.js';
+import unicorn from './index.js';
+
+const config = [
+	...xo,
+	unicorn.configs.recommended,
+	internal.configs.all,
+	{
+		languageOptions: {
+			globals: {
+				...globals.node,
+			},
+		},
+	},
+	{
+		ignores: [
+			'coverage',
+			'.cache-eslint-remote-tester',
+			'eslint-remote-tester-results',
+			'rules/utils/lodash.js',
+			'test/integration/{fixtures,fixtures-local}/**',
+		],
+	},
+	{
+		rules: {
+			'unicorn/escape-case': 'off',
+			'unicorn/expiring-todo-comments': 'off',
+			'unicorn/no-hex-escape': 'off',
+			'unicorn/no-null': 'error',
+			'unicorn/prefer-array-flat': ['error', {
+				functions: [
+					'flat',
+					'flatten',
+				],
+			}],
+			'unicorn/consistent-function-scoping': 'off',
+			'import/order': 'off',
+			'func-names': 'off',
+			'@stylistic/function-paren-newline': 'off',
+		},
+	},
+	{
+		files: [
+			'rules/*.js',
+		],
+		plugins: {
+			'eslint-plugin': eslintPlugin,
+		},
+		rules: {
+			...eslintPlugin.configs.all.rules,
+			'eslint-plugin/require-meta-docs-description': [
+				'error',
+				{
+					pattern: '.+',
+				},
+			],
+			'eslint-plugin/require-meta-docs-url': 'off',
+			'eslint-plugin/require-meta-has-suggestions': 'off',
+			'eslint-plugin/require-meta-schema': 'off',
+			'eslint-plugin/require-meta-schema-description': 'off',
+		},
+	},
+];
+
+export default config;