Adding support for eslint 9

packages/eslint-config-airbnb-base/eslint.config.js

@@ -0,0 +1,13 @@
+const base = require('./flat');
+
+module.exports = [
+  ...base,
+  { rules: { 'comma-dangle': 'off', 'max-len': 'off' } },
+  {
+    files: ['test/**'],
+    rules: {
+      'no-shadow': 'off',
+      'id-length': ['error', { min: 2, properties: 'never', exceptions: ['t'] }],
+    },
+  },
+];

packages/eslint-config-airbnb-base/flat.js

@@ -0,0 +1,44 @@
+const globals = require('globals');
+const importPlugin = require('eslint-plugin-import');
+
+const bestPractices = require('./rules/best-practices');
+const errors = require('./rules/errors');
+const es6 = require('./rules/es6');
+const imports = require('./rules/imports');
+const node = require('./rules/node');
+const strict = require('./rules/strict');
+const style = require('./rules/style');
+const variables = require('./rules/variables');
+
+module.exports = [
+  {
+    languageOptions: {
+      ecmaVersion: 2018,
+      sourceType: 'module',
+      globals: {
+        ...globals.es2015,
+        ...globals.node,
+      },
+      parserOptions: {
+        ecmaFeatures: {
+          generators: false,
+          objectLiteralDuplicateProperties: false,
+        },
+      },
+    },
+    plugins: {
+      import: importPlugin,
+    },
+    settings: imports.settings,
+    rules: {
+      ...bestPractices.rules,
+      ...errors.rules,
+      ...node.rules,
+      ...style.rules,
+      ...variables.rules,
+      ...es6.rules,
+      ...imports.rules,
+      ...strict.rules,
+    },
+  },
+];

packages/eslint-config-airbnb-base/package.json

@@ -15,6 +15,7 @@
     "./rules/imports": "./rules/imports.js",
     "./rules/strict": "./rules/strict.js",
     "./rules/variables": "./rules/variables.js",
+    "./flat": "./flat.js",
     "./package.json": "./package.json"
   },
   "scripts": {
@@ -72,21 +73,22 @@
     "babel-preset-airbnb": "^4.5.0",
     "babel-tape-runner": "^3.0.0",
     "eclint": "^2.8.1",
-    "eslint": "^7.32.0 || ^8.2.0",
-    "eslint-find-rules": "^4.1.0",
+    "eslint": "^7.32.0 || ^8.2.0 || ^9.0.0",
+    "eslint-find-rules": "^5.0.0",
     "eslint-plugin-import": "^2.30.0",
     "in-publish": "^2.0.1",
     "safe-publish-latest": "^2.0.0",
     "tape": "^5.9.0"
   },
   "peerDependencies": {
-    "eslint": "^7.32.0 || ^8.2.0",
+    "eslint": "^7.32.0 || ^8.2.0 || ^9.0.0",
     "eslint-plugin-import": "^2.30.0"
   },
   "engines": {
     "node": "^10.12.0 || >=12.0.0"
   },
   "dependencies": {
-    "confusing-browser-globals": "^1.0.11"
+    "confusing-browser-globals": "^1.0.11",
+    "globals": "^15.14.0"
   }
 }

packages/eslint-config-airbnb-base/test/requires.js

@@ -8,6 +8,7 @@ test('all entry points parse', (t) => {
   t.doesNotThrow(() => require('..'), 'index does not throw');
   t.doesNotThrow(() => require('../legacy'), 'legacy does not throw');
   t.doesNotThrow(() => require('../whitespace'), 'whitespace does not throw');
+  t.doesNotThrow(() => require('../flat'), 'flat does not throw');
 
   t.end();
 });

packages/eslint-config-airbnb-base/test/test-flat-parity.js

@@ -0,0 +1,54 @@
+import test from 'tape';
+
+import flatConfig from '../flat';
+
+import bestPractices from '../rules/best-practices';
+import errors from '../rules/errors';
+import es6 from '../rules/es6';
+import imports from '../rules/imports';
+import node from '../rules/node';
+import strict from '../rules/strict';
+import style from '../rules/style';
+import variables from '../rules/variables';
+
+test('flat config includes all rules from rule files', (t) => {
+  // The flat config is an array with one config object
+  t.ok(Array.isArray(flatConfig), 'flat config is an array');
+  t.equal(flatConfig.length, 1, 'flat config has one element');
+
+  const flatRules = flatConfig[0].rules;
+
+  // Merge rules in the same order as flat.js
+  const expectedRules = {
+    ...bestPractices.rules,
+    ...errors.rules,
+    ...node.rules,
+    ...style.rules,
+    ...variables.rules,
+    ...es6.rules,
+    ...imports.rules,
+    ...strict.rules,
+  };
+
+  const flatKeys = Object.keys(flatRules).sort();
+  const expectedKeys = Object.keys(expectedRules).sort();
+
+  t.deepEqual(flatKeys, expectedKeys, 'flat config has the same rule keys as combined rule files');
+
+  expectedKeys.forEach((key) => {
+    t.deepEqual(flatRules[key], expectedRules[key], `rule "${key}" has matching config`);
+  });
+
+  t.end();
+});
+
+test('flat config has required plugins and settings', (t) => {
+  const config = flatConfig[0];
+
+  t.ok(config.plugins.import, 'import plugin is present');
+  t.ok(config.settings, 'settings are present');
+  t.ok(config.languageOptions, 'languageOptions are present');
+  t.equal(config.languageOptions.sourceType, 'module', 'sourceType is module');
+
+  t.end();
+});

packages/eslint-config-airbnb-base/whitespace-async.js

@@ -4,7 +4,9 @@ const { isArray } = Array;
 const { entries } = Object;
 const { ESLint } = require('eslint');
 
-const baseConfig = require('.');
+// ESLint 9 transition-period API; will be moot once eslintrc is fully removed in ESLint 10+
+const isFlat = ESLint.configType === 'flat';
+const baseConfig = isFlat ? require('./flat') : require('.');
 const whitespaceRules = require('./whitespaceRules');
 
 const severities = ['off', 'warn', 'error'];
@@ -20,11 +22,10 @@ function getSeverity(ruleConfig) {
 }
 
 async function onlyErrorOnRules(rulesToError, config) {
-  const errorsOnly = { ...config };
-  const cli = new ESLint({
-    useEslintrc: false,
-    baseConfig: config
-  });
+  const errorsOnly = isFlat ? { rules: {} } : { ...config };
+  const cli = isFlat
+    ? new ESLint({ overrideConfigFile: true, overrideConfig: config })
+    : new ESLint({ useEslintrc: false, baseConfig: config });
   const baseRules = (await cli.calculateConfigForFile(require.resolve('./'))).rules;
 
   entries(baseRules).forEach((rule) => {

packages/eslint-config-airbnb-base/whitespace.js

@@ -50,12 +50,28 @@ if (CLIEngine) {
 } else {
   const path = require('path');
   const { execSync } = require('child_process');
+  const { ESLint } = require('eslint');
 
   // NOTE: ESLint adds runtime statistics to the output (so it's no longer JSON) if TIMING is set
-  module.exports = JSON.parse(String(execSync(path.join(__dirname, 'whitespace-async.js'), {
+  const ruleOverrides = JSON.parse(String(execSync(path.join(__dirname, 'whitespace-async.js'), {
     env: {
       ...process.env,
       TIMING: undefined,
     }
   })));
+
+  // ESLint 9 transition-period API; will be moot once eslintrc is fully removed in ESLint 10+
+  if (ESLint.configType === 'flat') {
+    // In flat mode, whitespace-async.js outputs only { rules: {} } since plugins
+    // are not JSON-serializable. Merge the rule overrides with the full flat config
+    // so consumers get a complete config with plugins, settings, and languageOptions.
+    const flatConfig = require('./flat');
+    const lastConfig = flatConfig[flatConfig.length - 1];
+    module.exports = [
+      ...flatConfig.slice(0, -1),
+      { ...lastConfig, rules: { ...lastConfig.rules, ...ruleOverrides.rules } },
+    ];
+  } else {
+    module.exports = ruleOverrides;
+  }
 }

packages/eslint-config-airbnb/eslint.config.js

@@ -0,0 +1,13 @@
+const airbnb = require('./flat');
+
+module.exports = [
+  ...airbnb,
+  { rules: { 'comma-dangle': 'off' } },
+  {
+    files: ['test/**'],
+    rules: {
+      'no-shadow': 'off',
+      'id-length': ['error', { min: 2, properties: 'never', exceptions: ['t'] }],
+    },
+  },
+];

packages/eslint-config-airbnb/flat-base.js

@@ -0,0 +1 @@
+module.exports = require('eslint-config-airbnb-base/flat');

packages/eslint-config-airbnb/flat-hooks.js

@@ -0,0 +1,20 @@
+const reactHooksPlugin = require('eslint-plugin-react-hooks');
+
+const reactHooks = require('./rules/react-hooks');
+
+module.exports = [
+  {
+    files: ['**/*.{js,jsx,mjs,cjs}'],
+    plugins: {
+      'react-hooks': reactHooksPlugin,
+    },
+    languageOptions: {
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+    },
+    rules: reactHooks.rules,
+  },
+];

packages/eslint-config-airbnb/flat.js

@@ -0,0 +1,30 @@
+const reactPlugin = require('eslint-plugin-react');
+const jsxA11yPlugin = require('eslint-plugin-jsx-a11y');
+
+const baseFlatConfig = require('eslint-config-airbnb-base/flat');
+
+const react = require('./rules/react');
+const reactA11y = require('./rules/react-a11y');
+
+module.exports = [
+  ...baseFlatConfig,
+  {
+    files: ['**/*.{js,jsx,mjs,cjs}'],
+    plugins: {
+      react: reactPlugin,
+      'jsx-a11y': jsxA11yPlugin,
+    },
+    languageOptions: {
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+    },
+    settings: react.settings,
+    rules: {
+      ...react.rules,
+      ...reactA11y.rules,
+    },
+  },
+];

packages/eslint-config-airbnb/package.json

@@ -12,6 +12,9 @@
     "./rules/react": "./rules/react.js",
     "./rules/react-a11y": "./rules/react-a11y.js",
     "./rules/react-hooks": "./rules/react-hooks.js",
+    "./flat": "./flat.js",
+    "./flat-base": "./flat-base.js",
+    "./flat-hooks": "./flat-hooks.js",
     "./package.json": "./package.json"
   },
   "scripts": {
@@ -73,8 +76,8 @@
     "babel-preset-airbnb": "^4.5.0",
     "babel-tape-runner": "^3.0.0",
     "eclint": "^2.8.1",
-    "eslint": "^7.32.0 || ^8.2.0",
-    "eslint-find-rules": "^4.1.0",
+    "eslint": "^7.32.0 || ^8.2.0 || ^9.0.0",
+    "eslint-find-rules": "^5.0.0",
     "eslint-plugin-import": "^2.30.0",
     "eslint-plugin-jsx-a11y": "^6.10.0",
     "eslint-plugin-react": "^7.36.1",
@@ -85,7 +88,7 @@
     "tape": "^5.9.0"
   },
   "peerDependencies": {
-    "eslint": "^7.32.0 || ^8.2.0",
+    "eslint": "^7.32.0 || ^8.2.0 || ^9.0.0",
     "eslint-plugin-import": "^2.30.0",
     "eslint-plugin-jsx-a11y": "^6.10.0",
     "eslint-plugin-react": "^7.36.1",

packages/eslint-config-airbnb/test/requires.js

@@ -10,6 +10,9 @@ test('all entry points parse', (t) => {
   t.doesNotThrow(() => require('../legacy'), 'legacy does not throw');
   t.doesNotThrow(() => require('../whitespace'), 'whitespace does not throw');
   t.doesNotThrow(() => require('../hooks'), 'hooks does not throw');
+  t.doesNotThrow(() => require('../flat'), 'flat does not throw');
+  t.doesNotThrow(() => require('../flat-base'), 'flat-base does not throw');
+  t.doesNotThrow(() => require('../flat-hooks'), 'flat-hooks does not throw');
 
   t.end();
 });