ESLint: Migrate to flat config format

.github/workflows/ci.yml

@@ -42,7 +42,7 @@ jobs:
             packages/**
             public/**
             tests/**
-            .eslintrc
+            eslint.config.mjs
             .template-lintrc.js
             ember-cli-build.js
             package.json

app/services/color-scheme.js

@@ -44,7 +44,6 @@ export default class DesignService extends Service {
    */
   watcherTask = restartableTask(async () => {
     let mediaQueryList = window.matchMedia('(prefers-color-scheme: dark)');
-    // eslint-disable-next-line no-constant-condition
     while (true) {
       let scheme = this.scheme;
       if (scheme === 'system') {

app/services/session.js

@@ -144,7 +144,6 @@ export default class SessionService extends Service {
   });
 
   windowEventWatcherTask = task(async () => {
-    // eslint-disable-next-line no-constant-condition
     while (true) {
       let event = await waitForEvent(window, 'message');
       if (event.origin !== window.location.origin || !event.data) {
@@ -161,7 +160,6 @@ export default class SessionService extends Service {
   });
 
   windowCloseWatcherTask = task(async window => {
-    // eslint-disable-next-line no-constant-condition
     while (true) {
       if (window.closed) {
         return { closed: true };

docs/ARCHITECTURE.md

@@ -50,7 +50,7 @@ These files have to do with the frontend:
   frontend; served under the root `/` url - (ignored in `.gitignore`)
 - `.ember-cli` - Settings for the `ember` command line interface
 - `ember-cli-build.js` - Contains the build specification for Broccoli
-- `.eslintrc.js` - Defines Javascript coding style guidelines (enforced during CI???)
+- `eslint.config.mjs` - Defines Javascript coding style guidelines
 - `node_modules/` - npm dependencies - (ignored in `.gitignore`)
 - `packages/crates-io-msw` - A mock backend used for testing
 - `package.json` - Defines the npm package and its dependencies

eslint.config.mjs

@@ -0,0 +1,197 @@
+import babelParser from '@babel/eslint-parser';
+import { FlatCompat } from '@eslint/eslintrc';
+import js from '@eslint/js';
+import ember from 'eslint-plugin-ember';
+import emberConcurrency from 'eslint-plugin-ember-concurrency';
+import importHelpers from 'eslint-plugin-import-helpers';
+import prettier from 'eslint-plugin-prettier';
+import globals from 'globals';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const compat = new FlatCompat({
+  baseDirectory: __dirname,
+  recommendedConfig: js.configs.recommended,
+  allConfig: js.configs.all,
+});
+
+export default [
+  {
+    ignores: [
+      '.git/**/*',
+      'crates/',
+      'playwright-report/',
+      'target/',
+      'test-results/',
+      'tmp/',
+      // unconventional js
+      'blueprints/*/files/',
+      'vendor/',
+      // compiled output
+      'dist/',
+      'tmp/',
+      // dependencies
+      'bower_components/',
+      'node_modules/',
+      // misc
+      'coverage/',
+      '!**/.*',
+      // ember-try
+      '.node_modules.ember-try/',
+      'bower.json.ember-try',
+      'package.json.ember-try',
+    ],
+  },
+  ...compat.extends(
+    'eslint:recommended',
+    'plugin:ember/recommended',
+    'plugin:qunit/recommended',
+    'plugin:qunit-dom/recommended',
+    'plugin:unicorn/recommended',
+    'plugin:prettier/recommended',
+  ),
+  {
+    plugins: {
+      ember,
+      'ember-concurrency': emberConcurrency,
+      prettier,
+      'import-helpers': importHelpers,
+    },
+
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+      },
+
+      parser: babelParser,
+      ecmaVersion: 2018,
+      sourceType: 'module',
+
+      parserOptions: {
+        requireConfigFile: false,
+
+        babelOptions: {
+          plugins: [
+            [
+              '@babel/plugin-proposal-decorators',
+              {
+                decoratorsBeforeExport: true,
+              },
+            ],
+          ],
+        },
+      },
+    },
+
+    rules: {
+      // it's fine to use `return` without a value and rely on the implicit `undefined` return value
+      'getter-return': 'off',
+
+      // declaration sort is taken care of by `import-helpers/order-imports`
+      'sort-imports': ['error', { ignoreDeclarationSort: true, ignoreCase: true }],
+
+      'prettier/prettier': 'error',
+
+      // disabled because we still use `this.set()` in a few places and it works just fine
+      'ember/classic-decorator-no-classic-methods': 'off',
+      // disabled because the alternatives are currently not worth the additional complexity
+      'ember/no-array-prototype-extensions': 'off',
+
+      'ember-concurrency/no-perform-without-catch': 'warn',
+      'ember-concurrency/require-task-name-suffix': 'error',
+
+      // disabled because of false positives in `assert.rejects()` calls
+      'qunit/require-expect': 'off',
+
+      // disabled because of false positives related to ember-concurrency usage
+      'unicorn/consistent-function-scoping': 'off',
+      'unicorn/explicit-length-check': ['error', { 'non-zero': 'not-equal' }],
+      // disabled because it conflicts with Ember.js conventions
+      'unicorn/no-anonymous-default-export': 'off',
+      // disabled because of false positives related to `EmberArray`
+      'unicorn/no-array-for-each': 'off',
+      // disabled because it is annoying in some cases...
+      'unicorn/no-await-expression-member': 'off',
+      // disabled because we need `null` since JSON has no `undefined`
+      'unicorn/no-null': 'off',
+      // disabled because this rule conflicts with prettier
+      'unicorn/no-nested-ternary': 'off',
+      // disabled because of unfixable false positives
+      'unicorn/prevent-abbreviations': 'off',
+      // disabled because we are targeting only browsers at the moment
+      'unicorn/prefer-global-this': 'off',
+      // disabled because we don't want to go all-in on ES6 modules for Node.js code yet
+      'unicorn/prefer-module': 'off',
+      // disabled because it seems unnecessary
+      'unicorn/prefer-number-properties': 'off',
+      // disabled because it seems unnecessary
+      'unicorn/prefer-reflect-apply': 'off',
+      // disabled because of false positives related to `EmberArray`
+      'unicorn/prefer-spread': 'off',
+      // disabled because it seems unnecessary
+      'unicorn/prefer-string-raw': 'off',
+      // disabled because of Sentry issues
+      'unicorn/prefer-string-replace-all': 'off',
+      // disabled because switch statements in JS are quite error-prone
+      'unicorn/prefer-switch': 'off',
+      // disabled because of false positives
+      'unicorn/consistent-destructuring': 'off',
+      'unicorn/filename-case': ['error', { case: 'kebabCase', ignore: ['^-'] }],
+
+      'import-helpers/order-imports': [
+        'error',
+        {
+          newlinesBetween: 'always',
+          groups: [
+            // Node.js built-in modules
+            '/^(assert|async_hooks|buffer|child_process|cluster|console|constants|crypto|dgram|dns|domain|events|fs|http|http2|https|inspector|module|net|os|path|perf_hooks|process|punycode|querystring|readline|repl|stream|string_decoder|timers|tls|trace_events|tty|url|util|v8|vm|zli)/',
+            // Testing modules
+            ['/^(qunit|ember-qunit|@ember/test-helpers|ember-exam|htmlbars-inline-precompile)$/', '/^ember-exam\\//'],
+            // Ember.js modules
+            ['/^@(ember|ember-data|glimmer)\\//', '/^(ember|ember-data|rsvp)$/', '/^ember-data\\//'],
+            ['module'],
+            ['/^crates-io\\//'],
+            ['parent', 'sibling', 'index'],
+          ],
+          alphabetize: { order: 'asc', ignoreCase: true },
+        },
+      ],
+    },
+  },
+
+  // test files
+  {
+    files: ['tests/**/*.js'],
+
+    rules: {
+      'unicorn/consistent-function-scoping': 'off',
+      'unicorn/prefer-dom-node-dataset': 'off',
+    },
+  },
+
+  // node files
+  {
+    files: [
+      'eslint.config.mjs',
+      '**/.template-lintrc.js',
+      '**/ember-cli-build.js',
+      '**/testem.js',
+      'blueprints/*/index.js',
+      'config/**/*.js',
+      'lib/*/index.js',
+      'server/**/*.js',
+    ],
+
+    languageOptions: {
+      globals: {
+        ...Object.fromEntries(Object.entries(globals.browser).map(([key]) => [key, 'off'])),
+        ...globals.node,
+      },
+
+      ecmaVersion: 2018,
+      sourceType: 'script',
+    },
+  },
+];