Convert to ESLint 9 flat config and move to pnpm (#19)

* Convert to ESLint 9 flat config and move to pnpm

* Update instrcutions

* Remove yarn.lock

* Add changelog entry

* Use newest packages

Author: SleeplessByte

.prettierignore

@@ -3,6 +3,7 @@
 
 # These are org-wide files (https://github.com/exercism/org-wide-files/)
 /.github/labels.yml
+/.github/workflows/pause-community-contributions.yml
 /.github/workflows/sync-labels.yml
 
 /CODE_OF_CONDUCT.md

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## 0.7.0
+
+- Use pnpm 9.6.0
+- Update to eslint 9+
+- Migrate to flat config
+
 ## 0.6.0
 
 - Upgrade to eslint 8+

README.md

@@ -1,46 +1,70 @@
 # @exercism/eslint-config-javascript
 
-This is the shared [`eslint`][web-eslint] configuration used by the [JavaScript track][git-javascript] (for students) and the files contributors and maintainers touch. [Shareable configs][web-shareable-configs] are designed to work with the `extends` feature of `.eslintrc` files. This means you can use the same configuration you're used to on [Exercism][web-exercism] in your on projects!
+This is the shared [`eslint`][web-eslint] configuration used by the [JavaScript track][git-javascript] (for students) and the files contributors and maintainers touch.
+[Shareable configs][web-shareable-configs] are designed to work with the `extends` feature of ESLint configuration files.
+This means you can use the same configuration you're used to on [Exercism][web-exercism] in your on projects!
 
 ## Usage
 
-To use the configuration for students, open your [eslint configuration][web-eslint-configuration] file, and add the following value to `extends`. For example, for JSON based configuration files:
+To use the configuration for students, open your [eslint configuration][web-eslint-configuration] file, and import the following file for the flat config.
+For example, for flat config configuration files:
 
-```json
-{
-  "extends": "@exercism/eslint-config-javascript"
-}
+```javascript
+import baseConfig from '@exercism/eslint-config-javascript';
+
+// ...
+export default [
+  ...baseConfig,
+  // ... your configuration
+];
 ```
 
-To use the configuration used by contributors and maintainers, add the following to `extends`:
+To use the configuration used by contributors and maintainers, add the following:
+
+```javascript
+import baseConfig from '@exercism/eslint-config-javascript/maintainers';
 
-```json
-{
-  "extends": "@exercism/eslint-config-javascript/maintainers"
-}
+// ...
+export default [
+  ...baseConfig,
+  // ... your configuration
+];
 ```
 
 ## Students configuration
 
-Find the student configuration [here](index.js). It's goal is to help detect and prevent common problems, without making _any_ decisions about code-style.
+Find the student configuration [here](index.mjs).
+It's goal is to help detect and prevent common problems, without making _any_ decisions about code-style.
 
 The rules are based on:
 
 - [`eslint:recommended`][web-eslint-recommended]
-- [`plugin:import`][git-eslint-plugin-import]
 - A few extra rules that catch common issues but are not enabled via the recommended plugin. See [this PR][git-javascript-pr-1094] for a bit of discussion and rationale.
 
-Because the [Exercism JavaScript track][git-javascript] is primarily focussing on running the exercises on Node, only `node` and `es2021` are turned on as environment, but when extending this configuration, you can add more (or turn those off).
+Because the [Exercism JavaScript track][git-javascript] is primarily focussing on running the exercises on Node, only `node` globals are turned on in the environment, but when extending this configuration, you can add more (or turn those off).
 
 ## Maintainers configuration
 
-Similar to the students configuration, and found [here](maintainers.js), it also includes the [`prettier` plugin][git-eslint-plugin-prettier] because we use [`prettier`][web-prettier] to achieve consistent code formatting. This plugin turns _off_ rules that conflict with formatting.
+Similar to the students configuration, and found [here](maintainers.mjs), it also includes the [`prettier` plugin][git-eslint-plugin-prettier] because we use [`prettier`][web-prettier] to achieve consistent code formatting.
+This plugin turns _off_ rules that conflict with formatting.
 
 Additionally, it doesn't have warnings but errors for most/all of the rules in the students configuration.
 
 ## Tooling configuration
 
-Because the tooling (such as the [JavaScript Analyzer][git-javascript-analyzer], [Representer][git-javascript-representer], and [Test Runner][git-javascript-test-runner]) are written in TypeScript, they don't use the same configuration files. If you're looking for those, or to build your own tools in TypeScript, go to [@exercism/eslint-config-tooling][git-eslint-config-tooling].
+Because the tooling (such as the [JavaScript Analyzer][git-javascript-analyzer], [Representer][git-javascript-representer], and [Test Runner][git-javascript-test-runner]) are written in TypeScript, they don't use the same configuration files.
+If you're looking for those, or to build your own tools in TypeScript, go to [@exercism/eslint-config-tooling][git-eslint-config-tooling].
+
+## Development
+
+If you want to work on this repository, install the dependencies using `corepack` and `pnpm`:
+
+```shell
+corepack enable pnpm
+corepack pnpm install
+```
+
+Because pnpm is configured to use isolated `node_modules` (symlinked), everything such as your tools and plugins inside your editor should keep working as expected.
 
 [git-eslint-config-tooling]: https://github.com/exercism/eslint-config-tooling
 [git-eslint-plugin-import]: https://github.com/benmosher/eslint-plugin-import

babel.config.cjs

@@ -0,0 +1,4 @@
+module.exports = {
+  presets: ['@exercism/babel-preset-javascript'],
+  plugins: [],
+};

eslint.config.mjs

@@ -0,0 +1,14 @@
+import maintainers from './maintainers.mjs';
+
+export default [
+  ...maintainers,
+  {
+    ignores: [
+      '.appends/**/*',
+      '.github/**/*',
+      '.vscode/**/*',
+      '.yarn/**/*',
+      '.pnp.*',
+    ],
+  },
+];

index.js

@@ -0,0 +1,82 @@
+import babelParser from '@babel/eslint-parser';
+import fs from 'fs';
+
+import eslint from '@eslint/js';
+import jestPlugin from 'eslint-plugin-jest';
+import prettierConfig from 'eslint-config-prettier';
+
+import globals from 'globals';
+
+const pkg = JSON.parse(
+  fs.readFileSync(new URL('./package.json', import.meta.url), 'utf8'),
+);
+
+/** @type {import('eslint').ESLint.Plugin} */
+const plugin = {
+  meta: {
+    name: pkg.name + '/maintainers',
+    version: pkg.version,
+  },
+};
+
+/** @type {import('eslint').Linter.Config} */
+export default [
+  {
+    ...eslint.configs.recommended,
+    plugins: {
+      jest: jestPlugin,
+      [plugin.meta.name]: plugin,
+    },
+    languageOptions: {
+      parser: babelParser,
+      parserOptions: {
+        ecmaVersion: 'latest',
+      },
+      globals: {
+        ...globals.node,
+      },
+    },
+
+    rules: {
+      ...eslint.configs.recommended.rules,
+
+      // eslint rules
+      'array-callback-return': ['warn', { checkForEach: false }],
+      'default-param-last': 'error',
+      eqeqeq: ['warn', 'smart'],
+      'linebreak-style': 'off',
+      'no-eval': ['error', { allowIndirect: true }],
+      'no-extend-native': 'warn',
+      'no-implicit-coercion': 'warn',
+      'no-promise-executor-return': 'warn',
+      'no-shadow': 'warn',
+      'no-unreachable-loop': 'warn',
+      'no-unsafe-optional-chaining': 'error',
+      'require-atomic-updates': 'warn',
+    },
+  },
+
+  {
+    // enable jest rules on test files
+    files: ['test/**', '**/*.spec.js*', '**/*.test.js*'],
+    ...jestPlugin.configs['flat/recommended'],
+    rules: {
+      ...jestPlugin.configs['flat/recommended'].rules,
+      'jest/no-disabled-tests': 'off',
+      'jest/no-test-prefixes': 'off',
+    },
+    languageOptions: {
+      globals: {
+        // Don't make jest globals available! These should not be available
+        // but imported from @jest/globals.
+        //
+        // ...globals.jest,
+      },
+    },
+  },
+
+  // https://github.com/import-js/eslint-plugin-import/pull/3018
+  // missing: import/* plugins
+
+  prettierConfig,
+];

index.mjs

@@ -0,0 +1,83 @@
+import babelParser from '@babel/eslint-parser';
+import fs from 'fs';
+
+import eslint from '@eslint/js';
+import jestPlugin from 'eslint-plugin-jest';
+import prettierConfig from 'eslint-config-prettier';
+
+import globals from 'globals';
+
+const pkg = JSON.parse(
+  fs.readFileSync(new URL('./package.json', import.meta.url), 'utf8'),
+);
+
+/** @type {import('eslint').ESLint.Plugin} */
+const plugin = {
+  meta: {
+    name: pkg.name + '/maintainers',
+    version: pkg.version,
+  },
+};
+
+/** @type {import('eslint').Linter.Config} */
+export default [
+  {
+    ...eslint.configs.recommended,
+    plugins: {
+      jest: jestPlugin,
+      [plugin.meta.name]: plugin,
+    },
+    languageOptions: {
+      parser: babelParser,
+      parserOptions: {
+        ecmaVersion: 'latest',
+        sourceType: undefined,
+      },
+      globals: {
+        ...globals.node,
+      },
+    },
+
+    rules: {
+      ...eslint.configs.recommended.rules,
+
+      // eslint rules
+      'array-callback-return': ['error', { checkForEach: true }],
+      'default-param-last': 'error',
+      eqeqeq: ['error', 'smart'],
+      'linebreak-style': 'off',
+      'no-eval': ['error', { allowIndirect: true }],
+      'no-extend-native': 'error',
+      'no-implicit-coercion': 'error',
+      'no-promise-executor-return': 'error',
+      'no-shadow': 'error',
+      'no-unreachable-loop': 'error',
+      'no-unsafe-optional-chaining': 'error',
+      'require-atomic-updates': 'error',
+    },
+  },
+
+  {
+    // enable jest rules on test files
+    files: ['test/**', '**/*.spec.js*', '**/*.test.js*'],
+    ...jestPlugin.configs['flat/recommended'],
+    rules: {
+      ...jestPlugin.configs['flat/recommended'].rules,
+      'jest/no-disabled-tests': 'off',
+      'jest/no-test-prefixes': 'off',
+    },
+    languageOptions: {
+      globals: {
+        // Don't make jest globals available! These should not be available
+        // but imported from @jest/globals.
+        //
+        // ...globals.jest,
+      },
+    },
+  },
+
+  // https://github.com/import-js/eslint-plugin-import/pull/3018
+  // missing: import/* plugins
+
+  prettierConfig,
+];