From c561084ff7447fd23a4935c196106cd9e7cfd305 Mon Sep 17 00:00:00 2001
From: Olivier Zalmanski <olivier.zalmanski@me.com>
Date: Mon, 4 Sep 2023 00:11:06 +0200
Subject: [PATCH] Support eslint flat config

---
 packages/eslint-config-airbnb-base/README.md  | 17 +++-
 packages/eslint-config-airbnb-base/flat.js    | 89 +++++++++++++++++++
 .../eslint-config-airbnb-base/package.json    |  2 +
 .../rules/imports.js                          |  3 +-
 4 files changed, 109 insertions(+), 2 deletions(-)
 create mode 100644 packages/eslint-config-airbnb-base/flat.js

diff --git a/packages/eslint-config-airbnb-base/README.md b/packages/eslint-config-airbnb-base/README.md
index 6ddc34dac1..834ca99264 100644
--- a/packages/eslint-config-airbnb-base/README.md
+++ b/packages/eslint-config-airbnb-base/README.md
@@ -60,7 +60,22 @@ Our default export contains all of our ESLint rules, including ECMAScript 6+. It
   npm install --save-dev eslint-config-airbnb-base eslint@^#.#.# eslint-plugin-import@^#.#.#
   ```
 
-2. Add `"extends": "airbnb-base"` to your .eslintrc.
+2. Use it in your eslint config.
+
+  If you use the new flat format, add the following to your eslint.config.js:
+
+  ```javascript
+  const airbnbBase = require('eslint-config-airbnb-base/flat')
+
+  module.exports = [
+    ...airbnbBase,
+    {
+      // any other config
+    }
+  ]
+  ```
+
+  If you still use the regular format: add `"extends": "airbnb-base"` to your .eslintrc.
 
 ### eslint-config-airbnb-base/legacy
 
diff --git a/packages/eslint-config-airbnb-base/flat.js b/packages/eslint-config-airbnb-base/flat.js
new file mode 100644
index 0000000000..d18b40a01f
--- /dev/null
+++ b/packages/eslint-config-airbnb-base/flat.js
@@ -0,0 +1,89 @@
+/**
+ * Changes to support the flat config format:
+ * - The `extends` key has been deprecated.
+ * - The `parserOptions` key has been moved under the new `languageOptions` key.
+ * - The `env` key has been deprecated and moved to `languageOptions.globals`.
+ * - The `plugins` key is no longer a list but an object.
+ */
+
+const importPlugin = require('eslint-plugin-import/config/flat');
+const envs = require('globals');
+const {
+  extends: airbnbRules,
+  ...airbnbConfig
+} = require('.');
+
+const envMapping = {
+  builtin: 'builtin',
+  es5: 'es5',
+  es6: 'es2015',
+  es2016: 'es2015',
+  es2017: 'es2017',
+  es2018: 'es2017',
+  es2019: 'es2017',
+  es2020: 'es2020',
+  es2021: 'es2021',
+  es2022: 'es2021',
+  es2023: 'es2021',
+  es2024: 'es2021',
+  browser: 'browser',
+  worker: 'worker',
+  node: 'node',
+  nodeBuiltin: 'nodeBuiltin',
+  commonjs: 'commonjs',
+  amd: 'amd',
+  mocha: 'mocha',
+  jasmine: 'jasmine',
+  jest: 'jest',
+  qunit: 'qunit',
+  phantomjs: 'phantomjs',
+  couch: 'couch',
+  rhino: 'rhino',
+  nashorn: 'nashorn',
+  wsh: 'wsh',
+  jquery: 'jquery',
+  yui: 'yui',
+  shelljs: 'shelljs',
+  prototypejs: 'prototypejs',
+  meteor: 'meteor',
+  mongo: 'mongo',
+  applescript: 'applescript',
+  serviceworker: 'serviceworker',
+  atomtest: 'atomtest',
+  embertest: 'embertest',
+  protractor: 'protractor',
+  'shared-node-browser': 'shared-node-browser',
+  webextensions: 'webextensions',
+  greasemonkey: 'greasemonkey',
+  devtools: 'devtools',
+};
+
+function convertIntoEslintFlatConfig(config) {
+  const {
+    env, // convert to explicit `globals` list
+    parserOptions, // move into `languageOptions`
+    plugins, // remove the `plugins` key as it will be spread directly during export
+    ...oldConfig
+  } = config;
+  return {
+    ...oldConfig,
+    languageOptions: {
+      ...('env' in config && {
+        globals: Object.fromEntries(
+          Object.keys(env)
+            .filter((key) => env[key] === true && key in envMapping && envMapping[key] in envs)
+            .flatMap((key) => Object.entries(envs[envMapping[key]]))
+        ),
+        ...('parserOptions' in config && {
+          parserOptions,
+        }),
+      }),
+    },
+  };
+}
+
+module.exports = [
+  ...airbnbRules.map((rule) => convertIntoEslintFlatConfig(require(rule))),
+  convertIntoEslintFlatConfig(airbnbConfig),
+  ...importPlugin,
+];
diff --git a/packages/eslint-config-airbnb-base/package.json b/packages/eslint-config-airbnb-base/package.json
index 39c0fdf944..d78e68ac73 100644
--- a/packages/eslint-config-airbnb-base/package.json
+++ b/packages/eslint-config-airbnb-base/package.json
@@ -5,6 +5,7 @@
   "main": "index.js",
   "exports": {
     ".": "./index.js",
+    "./flat": "./flat.js",
     "./legacy": "./legacy.js",
     "./whitespace": "./whitespace.js",
     "./rules/best-practices": "./rules/best-practices.js",
@@ -88,6 +89,7 @@
   },
   "dependencies": {
     "confusing-browser-globals": "^1.0.11",
+    "globals": "^13.21.0",
     "object.entries": "^1.1.6"
   }
 }
diff --git a/packages/eslint-config-airbnb-base/rules/imports.js b/packages/eslint-config-airbnb-base/rules/imports.js
index d36e4908fa..7a5cb39cca 100644
--- a/packages/eslint-config-airbnb-base/rules/imports.js
+++ b/packages/eslint-config-airbnb-base/rules/imports.js
@@ -91,7 +91,8 @@ module.exports = {
         '**/protractor.conf.js', // protractor config
         '**/protractor.conf.*.js', // protractor config
         '**/karma.conf.js', // karma config
-        '**/.eslintrc.js' // eslint config
+        '**/.eslintrc.js', // eslint config
+        '**/eslint.config.js', // eslint flat config
       ],
       optionalDependencies: false,
     }],