chore: migrate to flat ESLint config

eslint.config.js

@@ -0,0 +1,139 @@
+'use strict';
+
+const pluginEslintCommentsConfigs = require('@eslint-community/eslint-plugin-eslint-comments/configs');
+const pluginTypeScriptESLint = require('@typescript-eslint/eslint-plugin');
+const parserTypeScriptESLint = require('@typescript-eslint/parser');
+const pluginESLintPlugin = require('eslint-plugin-eslint-plugin');
+const pluginImport = require('eslint-plugin-import');
+const pluginN = require('eslint-plugin-n');
+const pluginPrettier = require('eslint-plugin-prettier');
+const pluginPrettierRecommended = require('eslint-plugin-prettier/recommended');
+const globals = require('./src/globals.json');
+
+/** @type {import('eslint').Linter.FlatConfig[]} */
+const config = [
+  { files: ['**/*.{js,jsx,cjs,mjs,ts,tsx,cts,mts}'] },
+  { ignores: ['.yarn', 'coverage/', 'lib/', 'src/rules/__tests__/fixtures'] },
+  {
+    plugins: {
+      // @ts-expect-error types are currently not considered compatible currently
+      //  todo: suspect this is because of differences in ESLint (types) versions
+      '@typescript-eslint': pluginTypeScriptESLint,
+      ...pluginEslintCommentsConfigs.recommended.plugins,
+      import: pluginImport,
+      'eslint-plugin': pluginESLintPlugin,
+      n: pluginN,
+      prettier: pluginPrettier,
+    },
+    languageOptions: { parser: parserTypeScriptESLint },
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error',
+    },
+    rules: {
+      ...pluginESLintPlugin.configs['flat/recommended'].rules,
+      ...pluginEslintCommentsConfigs.recommended.rules,
+      ...pluginPrettierRecommended.rules,
+    },
+  },
+  {
+    rules: {
+      '@typescript-eslint/array-type': ['error', { default: 'array-simple' }],
+      '@typescript-eslint/no-require-imports': 'error',
+      '@typescript-eslint/ban-ts-comment': 'error',
+      '@typescript-eslint/no-empty-object-type': 'error',
+      '@typescript-eslint/no-unsafe-function-type': 'error',
+      '@typescript-eslint/no-wrapper-object-types': 'error',
+      '@typescript-eslint/consistent-type-imports': [
+        'error',
+        { disallowTypeAnnotations: false, fixStyle: 'inline-type-imports' },
+      ],
+      '@typescript-eslint/no-import-type-side-effects': 'error',
+      '@typescript-eslint/no-unused-vars': 'error',
+      '@eslint-community/eslint-comments/no-unused-disable': 'error',
+      'eslint-plugin/require-meta-docs-description': [
+        'error',
+        { pattern: '^(Enforce|Require|Disallow|Suggest|Prefer)' },
+      ],
+      'eslint-plugin/test-case-property-ordering': 'error',
+      'no-else-return': 'error',
+      'no-negated-condition': 'error',
+      eqeqeq: ['error', 'smart'],
+      strict: 'error',
+      'prefer-template': 'error',
+      'object-shorthand': [
+        'error',
+        'always',
+        { avoidExplicitReturnArrows: true },
+      ],
+      'prefer-destructuring': [
+        'error',
+        { VariableDeclarator: { array: true, object: true } },
+      ],
+      'sort-imports': ['error', { ignoreDeclarationSort: true }],
+      'require-unicode-regexp': 'error',
+      // TS covers these 2
+      'n/no-missing-import': 'off',
+      'n/no-missing-require': 'off',
+      'n/no-unsupported-features/es-syntax': 'off',
+      'n/no-unsupported-features/es-builtins': 'error',
+      'import/no-commonjs': 'error',
+      'import/no-duplicates': 'error',
+      'import/no-extraneous-dependencies': 'error',
+      'import/no-unused-modules': 'error',
+      'import/order': [
+        'error',
+        { alphabetize: { order: 'asc' }, 'newlines-between': 'never' },
+      ],
+      'padding-line-between-statements': [
+        'error',
+        { blankLine: 'always', prev: '*', next: 'return' },
+        { blankLine: 'always', prev: ['const', 'let', 'var'], next: '*' },
+        {
+          blankLine: 'any',
+          prev: ['const', 'let', 'var'],
+          next: ['const', 'let', 'var'],
+        },
+        { blankLine: 'always', prev: 'directive', next: '*' },
+        { blankLine: 'any', prev: 'directive', next: 'directive' },
+      ],
+
+      'prefer-spread': 'error',
+      'prefer-rest-params': 'error',
+      'prefer-const': ['error', { destructuring: 'all' }],
+      'no-var': 'error',
+      curly: 'error',
+    },
+  },
+  {
+    files: ['*.js'],
+    rules: {
+      '@typescript-eslint/no-require-imports': 'off',
+    },
+  },
+  {
+    files: ['*.test.js', '*.test.ts'],
+    languageOptions: { globals },
+  },
+  {
+    files: [
+      '.eslint-doc-generatorrc.js',
+      'eslint.config.js',
+      'babel.config.js',
+    ],
+    languageOptions: {
+      sourceType: 'commonjs',
+    },
+    rules: {
+      '@typescript-eslint/no-require-imports': 'off',
+      'import/no-commonjs': 'off',
+    },
+  },
+  {
+    files: ['*.d.ts'],
+    rules: {
+      strict: 'off',
+    },
+  },
+];
+
+module.exports = config;

jest.config.ts

@@ -1,6 +1,4 @@
-import { version as eslintVersion } from 'eslint/package.json';
 import type { Config } from 'jest';
-import * as semver from 'semver';
 
 const config = {
   clearMocks: true,
@@ -36,11 +34,4 @@ const config = {
   ],
 } satisfies Config;
 
-if (semver.major(eslintVersion) !== 8) {
-  // our eslint config only works for v8
-  config.projects = config.projects.filter(
-    ({ displayName }) => displayName !== 'lint',
-  );
-}
-
 export default config;

package.json

@@ -31,7 +31,7 @@
   "scripts": {
     "build": "babel --extensions .js,.ts src --out-dir lib --copy-files && rimraf --glob lib/__tests__ 'lib/**/__tests__'",
     "postinstall": "is-ci || husky",
-    "lint": "eslint . --ignore-pattern '!.eslintrc.js' --ext js,ts",
+    "lint": "eslint .",
     "prepack": "rimraf lib && yarn build",
     "prepublishOnly": "pinst --disable",
     "prettier:check": "prettier --check 'docs/**/*.md' README.md '.github/**' package.json tsconfig.json src/globals.json .yarnrc.yml",

tsconfig.json

@@ -20,10 +20,11 @@
   },
   "files": [
     ".eslint-doc-generatorrc.js",
-    ".eslintrc.js",
+    "eslint.config.js",
     "babel.config.js",
     "eslint-remote-tester.config.ts",
-    "jest.config.ts"
+    "jest.config.ts",
+    "types.d.ts"
   ],
   "include": ["src/**/*"],
   "exclude": ["src/rules/__tests__/fixtures/**/*"]

types.d.ts

@@ -0,0 +1,38 @@
+declare module 'eslint-plugin-eslint-plugin' {
+  import type * as ESLint from 'eslint';
+
+  const plugin: ESLint.ESLint.Plugin & {
+    configs: {
+      all: ESLint.Linter.LegacyConfig;
+      'all-type-checked': ESLint.Linter.LegacyConfig;
+      recommended: ESLint.Linter.LegacyConfig;
+      rules: ESLint.Linter.LegacyConfig;
+      tests: ESLint.Linter.LegacyConfig;
+      'rules-recommended': ESLint.Linter.LegacyConfig;
+      'tests-recommended': ESLint.Linter.LegacyConfig;
+
+      'flat/all': ESLint.Linter.FlatConfig;
+      'flat/all-type-checked': ESLint.Linter.FlatConfig;
+      'flat/recommended': ESLint.Linter.FlatConfig;
+      'flat/rules': ESLint.Linter.FlatConfig;
+      'flat/tests': ESLint.Linter.FlatConfig;
+      'flat/rules-recommended': ESLint.Linter.FlatConfig;
+      'flat/tests-recommended': ESLint.Linter.FlatConfig;
+    };
+  };
+  export = plugin;
+}
+
+// todo: see https://github.com/eslint-community/eslint-plugin-eslint-comments/pull/246
+declare module '@eslint-community/eslint-plugin-eslint-comments/configs' {
+  import type * as ESLint from 'eslint';
+
+  const configs: {
+    recommended: ESLint.Linter.FlatConfig & {
+      plugins: {
+        '@eslint-community/eslint-plugin-eslint-comments': ESLint.ESLint.Plugin;
+      };
+    };
+  };
+  export = configs;
+}