Update ESLint to v9, drop support for Node.js v16 (#2250)

.github/workflows/main.yml

@@ -16,19 +16,20 @@ jobs:
       matrix:
         node-version:
           - 20
-          - 16
+          - 18
         os:
           - ubuntu-latest
           - windows-latest
-        include:
-          - os: ubuntu-latest
-            node-version: 18
+        # Even numbers of node-version
+        # include:
+        #   - os: ubuntu-latest
+        #     node-version: 18
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
-      - run: npm install
+      - run: npm install --legacy-peer-deps
       - run: npx ava
   lint-test:
     runs-on: ${{ matrix.os }}
@@ -43,7 +44,7 @@ jobs:
         with:
           # Locked due to the difference of `zlib.gzipSync()` between Node.js versions
           node-version: 20
-      - run: npm install
+      - run: npm install --legacy-peer-deps
       - run: npm run lint
       - run: npx del-cli test/snapshots --verbose
       # Force update snapshots, https://github.com/avajs/ava/discussions/2754
@@ -61,7 +62,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
-      - run: npm install
+      - run: npm install --legacy-peer-deps
       - run: npm run run-rules-on-codebase
   integration:
     name: Integration test (${{ matrix.group }})
@@ -84,5 +85,5 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
-      - run: npm install
+      - run: npm install --legacy-peer-deps
       - run: npm run integration -- --group ${{ matrix.group }}

package.json

@@ -51,7 +51,7 @@
 	"dependencies": {
 		"@babel/helper-validator-identifier": "^7.22.20",
 		"@eslint-community/eslint-utils": "^4.4.0",
-		"@eslint/eslintrc": "^2.1.4",
+		"@eslint/eslintrc": "^3.0.0",
 		"ci-info": "^4.0.0",
 		"clean-regexp": "^1.0.0",
 		"core-js-compat": "^3.34.0",
@@ -69,20 +69,21 @@
 	"devDependencies": {
 		"@babel/code-frame": "^7.23.5",
 		"@babel/core": "^7.23.6",
-		"@babel/eslint-parser": "^7.23.3",
+		"@babel/eslint-parser": "^7.24.1",
 		"@lubien/fixture-beta-package": "^1.0.0-beta.1",
 		"@typescript-eslint/parser": "^7.5.0",
 		"ava": "^6.0.1",
 		"c8": "^8.0.1",
 		"chalk": "^5.3.0",
 		"enquirer": "^2.4.1",
-		"eslint": "^8.56.0",
+		"eslint": "^9.0.0",
 		"eslint-ava-rule-tester": "^5.0.1",
 		"eslint-doc-generator": "^1.7.0",
 		"eslint-plugin-eslint-plugin": "^5.2.1",
 		"eslint-plugin-internal-rules": "file:./scripts/internal-rules/",
 		"eslint-remote-tester": "^3.0.1",
 		"eslint-remote-tester-repositories": "^1.0.1",
+		"espree": "^10.0.0",
 		"execa": "^8.0.1",
 		"listr": "^0.14.3",
 		"lodash-es": "^4.17.21",

test/better-regex.mjs

@@ -1,8 +1,6 @@
-import {createRequire} from 'node:module';
-import {getTester} from './utils/test.mjs';
+import {getTester, parsers} from './utils/test.mjs';
 
 const {test} = getTester(import.meta);
-const require = createRequire(import.meta.url);
 
 const MESSAGE_ID = 'better-regex';
 
@@ -220,21 +218,6 @@ test({
 			errors: createError('[0-9]', '\\d'),
 			output: 'const foo = new RegExp(\'\\\\d\', \'ig\')',
 		},
-		{
-			code: 'const foo = new RegExp(/[0-9]/)',
-			errors: createError('/[0-9]/', '/\\d/'),
-			output: 'const foo = new RegExp(/\\d/)',
-		},
-		{
-			code: 'const foo = new RegExp(/[0-9]/, \'ig\')',
-			errors: createError('/[0-9]/', '/\\d/'),
-			output: 'const foo = new RegExp(/\\d/, \'ig\')',
-		},
-		{
-			code: 'const foo = new RegExp(/[0-9]/)',
-			errors: createError('/[0-9]/', '/\\d/'),
-			output: 'const foo = new RegExp(/\\d/)',
-		},
 		{
 			code: 'const foo = new RegExp(/[0-9]/, \'ig\')',
 			errors: createError('/[0-9]/', '/\\d/'),
@@ -310,7 +293,9 @@ test({
 					message: 'Problem parsing /(/: \n\n/(/\n  ^\nUnexpected token: "/" at 1:2.',
 				},
 			],
-			parser: require.resolve('@typescript-eslint/parser'),
+			languageOptions: {
+				parser: parsers.typescript,
+			},
 		},
 
 		// Not fixable

test/catch-error-name.mjs

@@ -29,7 +29,6 @@ function invalidTestCase(options) {
 
 test({
 	valid: [
-		'try {} catch (error) {}',
 		{
 			code: 'try {} catch (err) {}',
 			options: [{name: 'err'}],
@@ -900,12 +899,14 @@ test.typescript({
 
 test.babel({
 	testerOptions: {
-		parserOptions: {
-			babelOptions: {
-				parserOpts: {
-					plugins: [
-						['decorators', {decoratorsBeforeExport: true}],
-					],
+		languageOptions: {
+			parserOptions: {
+				babelOptions: {
+					parserOpts: {
+						plugins: [
+							['decorators', {decoratorsBeforeExport: true}],
+						],
+					},
 				},
 			},
 		},

test/consistent-destructuring.mjs

@@ -444,7 +444,7 @@ test({
 						b
 					}
 				} = foo;
-				console.log(foo.a.c);
+				console.log(foo.a.c); // 2
 			`,
 			errors: [{
 				message: 'Use destructured variables over properties.',
@@ -453,15 +453,15 @@ test({
 		{
 			code: outdent`
 				const {a} = foo;
-				console.log(foo.a);
+				console.log(foo.a); // 2
 			`,
 			errors: [{
 				message: 'Use destructured variables over properties.',
 				suggestions: [{
 					desc: 'Replace `foo.a` with destructured property `a`.',
 					output: outdent`
 						const {a} = foo;
-						console.log(a);
+						console.log(a); // 2
 					`,
 				}],
 			}],

test/consistent-function-scoping.mjs

@@ -15,9 +15,11 @@ const createError = (functionNameWithKind, loc) => ({
 
 test({
 	testerOptions: {
-		parserOptions: {
-			ecmaFeatures: {
-				jsx: true,
+		languageOptions: {
+			parserOptions: {
+				ecmaFeatures: {
+					jsx: true,
+				},
 			},
 		},
 	},
@@ -473,12 +475,6 @@ test({
 			`,
 			errors: [createError('arrow function \'doBar\'')],
 		},
-		{
-			code: outdent`
-				const doFoo = () => bar => bar;
-			`,
-			errors: [createError('arrow function')],
-		},
 		// `this`
 		{
 			code: outdent`
@@ -628,9 +624,9 @@ test({
 		},
 		// Actual message
 		{
-			code: 'function foo() { async function* bar() {} }',
+			code: 'function foo() { async function* baz() {} }',
 			errors: [{
-				message: 'Move async generator function \'bar\' to the outer scope.',
+				message: 'Move async generator function \'baz\' to the outer scope.',
 			}],
 		},
 		// React Hooks

test/empty-brace-spaces.mjs

@@ -16,13 +16,12 @@ const cases = [
 	'switch (foo) {case bar: {/* */}}',
 	'switch (foo) {default: {/* */}}',
 	'try {/* */} catch(foo){}',
-	'try {} catch(foo){/* */}',
+	'try {} catch(bar){/* */}',
 	'try {} catch(foo){} finally {/* */}',
 	'do {/* */} while (foo)',
 	'while (foo){/* */}',
 	'foo = () => {/* */}',
 	'foo = function (){/* */}',
-	'function foo(){/* */}',
 	'foo = {/* */}',
 	'class Foo {bar() {/* */}}',
 	'foo = class {bar() {/* */}}',
@@ -49,11 +48,11 @@ test({
 		].flatMap(body => allCases.map(code => code.replace(SPACES_PLACEHOLDER, body))),
 		// Not empty
 		...cases.map(code => code.replace(SPACES_PLACEHOLDER, 'unicorn')),
-		...classBodyCases.map(code => code.replace(SPACES_PLACEHOLDER, 'bar() {}')),
+		...classBodyCases.map(code => code.replace(SPACES_PLACEHOLDER, 'baz() {}')),
 		// `with`
 		{
 			code: 'with (foo) {}',
-			parserOptions: {ecmaVersion: 5, sourceType: 'script'},
+			languageOptions: {ecmaVersion: 5, sourceType: 'script'},
 		},
 		// We don't check these cases
 		...ignoredCases.map(code => code.replace(SPACES_PLACEHOLDER, '   ')),
@@ -75,7 +74,7 @@ test({
 			code: 'with (foo) {     }',
 			output: 'with (foo) {}',
 			errors: 1,
-			parserOptions: {ecmaVersion: 5, sourceType: 'script'},
+			languageOptions: {ecmaVersion: 5, sourceType: 'script'},
 		},
 	],
 });
@@ -94,9 +93,11 @@ test.snapshot({
 });
 
 const enableBabelPlugins = plugins => ({
-	babelOptions: {
-		parserOpts: {
-			plugins,
+	parserOptions: {
+		babelOptions: {
+			parserOpts: {
+				plugins,
+			},
 		},
 	},
 });
@@ -110,19 +111,19 @@ test.babel({
 				};
 			`,
 			output: 'const foo = do     {};',
-			parserOptions: enableBabelPlugin('doExpressions'),
+			languageOptions: enableBabelPlugin('doExpressions'),
 			errors: 1,
 		},
 		{
 			code: 'const record = #{    };',
 			output: 'const record = #{};',
-			parserOptions: enableBabelPlugin(['recordAndTuple', {syntaxType: 'hash'}]),
+			languageOptions: enableBabelPlugin(['recordAndTuple', {syntaxType: 'hash'}]),
 			errors: 1,
 		},
 		{
 			code: 'const record = {|    |};',
 			output: 'const record = {||};',
-			parserOptions: enableBabelPlugin(['recordAndTuple', {syntaxType: 'bar'}]),
+			languageOptions: enableBabelPlugin(['recordAndTuple', {syntaxType: 'bar'}]),
 			errors: 1,
 		},
 		{
@@ -137,14 +138,14 @@ test.babel({
 					static    {}
 				}
 			`,
-			parserOptions: enableBabelPlugin('classStaticBlock'),
+			languageOptions: enableBabelPlugin('classStaticBlock'),
 			errors: 1,
 		},
 		// ESLint can't parse this now
 		// {
 		// 	code: 'const foo = module     {    };',
 		// 	output: 'const foo = module     {};',
-		// 	parserOptions: enableBabelPlugin('moduleBlocks'),
+		// 	languageOptions: enableBabelPlugin('moduleBlocks'),
 		// 	errors: 1
 		// },
 		{
@@ -153,7 +154,7 @@ test.babel({
 				};
 			`,
 			output: 'const foo = async    do    {};',
-			parserOptions: enableBabelPlugins(['doExpressions', 'asyncDoExpressions']),
+			languageOptions: enableBabelPlugins(['doExpressions', 'asyncDoExpressions']),
 			errors: 1,
 		},
 	],