feat!: add conditional TypeScript support to the ESLint config. (#146)

* feat!: add conditional TypeScript support to the ESLint config. (#124)

BREAKING CHANGE: Drops support for `eslint` ^6.8.0; `@edx/eslint-config` must now be used with at least `eslint` versions ^7.32.0 or ^8.2.0.

* refactor: updated package-lock

* refactor: updated typescript-eslint parser & plugin

* refactor: updated package-lock

---------

Co-authored-by: Adam Stankiewicz <agstanki@gmail.com>
Co-authored-by: Bilal Qamar <59555732+BilalQamar95@users.noreply.github.com>

.eslintrc.js

@@ -1,3 +1,21 @@
+const path = require('path');
+const fs = require('fs');
+
+/**
+ * TypeScript configuration for ESLint:
+ *
+ * Determine whether a `tsconfig.json` file exists in the root folder of the consuming
+ * project. If it exists, ensure ESLint is configured for TypeScript appropriately.
+ */
+const typeScriptParserOptions = {};
+const typeScriptExtensions = [];
+const tsConfigPath = path.resolve(process.cwd(), 'tsconfig.json');
+if (fs.existsSync(tsConfigPath)) {
+  typeScriptParserOptions.project = tsConfigPath;
+  typeScriptExtensions.push('airbnb-typescript');
+}
+/* End TypeScript configuration for ESLint */
+
 module.exports = {
   env: {
     es6: true,
@@ -11,7 +29,11 @@ module.exports = {
     // as peer dependencies.
     'airbnb',
     'airbnb/hooks',
+    ...typeScriptExtensions,
   ],
+  parserOptions: {
+    ...typeScriptParserOptions,
+  },
   // If you add rule overrides here, add code to test.js that proves you formatted it right.
   rules: {
     'class-methods-use-this': 'off',

README.md

@@ -1,26 +1,35 @@
-[![Build Status](https://api.travis-ci.org/edx/eslint-config.svg?branch=master)](https://travis-ci.org/edx/eslint-config)
+[![Build Status](https://github.com/openedx/eslint-config/actions/workflows/release.yml/badge.svg)](https://github.com/openedx/eslint-config/actions/workflows/release.yml/)
 [![NPM Version](https://img.shields.io/npm/v/@edx/eslint-config.svg)](https://www.npmjs.com/package/@edx/eslint-config)
 [![npm_downloads](https://img.shields.io/npm/dt/@edx/eslint-config.svg)](https://www.npmjs.com/package/@edx/eslint-config)
 [![license](https://img.shields.io/npm/l/@edx/eslint-config.svg)](https://github.com/openedx/eslint-config/blob/master/LICENSE)
 [![semantic release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
 
-# eslint-config
+# @edx/eslint-config
 
 ## Installation
 
 If you're using @edx/frontend-build, then you'll get this package for free. Otherwise, you can install it via:
 
-```
+```shell
 npx install-peerdeps --dev @edx/eslint-config
 ```
 
 This will install the package and all of its peer dependencies.
 
 Then, once it's installed, create an `.eslintrc.js` file in the top-level directory of your project with the following contents:
 
-```
+```js
 module.exports = {
   extends: "@edx/eslint-config",
 }
-
 ```
+
+### Using TypeScript
+
+If `@edx/eslint-config` detects a `tsconfig.json` file in the root folder of your project, it will optionally configure ESLint to add support for TypeScript. If a `tsconfig.json` file exists, the ESLint config will:
+* Extend `airbnb-typescript` ([source](https://www.npmjs.com/package/eslint-config-airbnb-typescript)).
+* Configure `parserOptions.project` to point to the `tsconfig.json` file in the root folder of your project.
+
+`airbnb-typescript` may only be extended if a `tsconfig.json` file exists in your project.
+
+If your `tsconfig.json` file is defined somewhere other than the root folder of your project, you may override the default ESLint configuration by extending `airbnb-typescript` and including the path to your `tsconfig.json` file in the `parserOptions.project` ESLint configuration.