Update ESLint to v9 (#1796)

* Convert to flat config with FlatCompat

* Remove FlatCompat

* Update to ESLint v9

app/components/admin/SaveButton.tsx

@@ -14,6 +14,7 @@ export const SaveButton: FC<SaveButtonProps> = ({
 }) => {
   const isSubmitting = useIsSubmitting();
   const { isValid } = useFormContext();
+  // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
   const disabled = disabledProp || isSubmitting || !isValid;
 
   return (

app/hooks/useSse.tsx

@@ -5,6 +5,7 @@ const eventSources = new Map<
   { eventSource: EventSource; refCount: number }
 >();
 
+// eslint-disable-next-line @typescript-eslint/no-unnecessary-type-parameters
 export function useSse<T>(url: string | URL, onMessage: (data: T) => void) {
   useEffect(() => {
     const eventSourceData = eventSources.get(url);

app/types/validateShow.ts

@@ -9,7 +9,7 @@ type DeepNonNullable<T> = T extends (infer U)[]
 /**
  * Ensure that all of an object's properties are not null.
  */
-function validate<T>(obj: T): boolean {
+function validate(obj: Record<string, unknown> | null): boolean {
   if (obj === null) return false;
   if (typeof obj !== 'object') return true;
   for (const key in obj) {

eslint.config.js

@@ -0,0 +1,158 @@
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+import { fixupPluginRules, includeIgnoreFile } from '@eslint/compat';
+import js from '@eslint/js';
+import prettier from 'eslint-config-prettier';
+import _import from 'eslint-plugin-import';
+import jsxA11y from 'eslint-plugin-jsx-a11y';
+import noOnlyTests from 'eslint-plugin-no-only-tests';
+import playwright from 'eslint-plugin-playwright';
+import react from 'eslint-plugin-react';
+import reactHooks from 'eslint-plugin-react-hooks';
+import simpleImportSort from 'eslint-plugin-simple-import-sort';
+import unicorn from 'eslint-plugin-unicorn';
+import unusedImports from 'eslint-plugin-unused-imports';
+import globals from 'globals';
+import tseslint from 'typescript-eslint';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const gitignorePath = path.resolve(__dirname, '.gitignore');
+
+export default tseslint.config(
+  js.configs.recommended,
+  react.configs.flat.recommended,
+  react.configs.flat['jsx-runtime'],
+  // This doesn't work yet
+  // reactHooks.configs.recommended,
+  jsxA11y.flatConfigs.recommended,
+  playwright.configs['flat/recommended'],
+
+  ...tseslint.configs.recommendedTypeChecked,
+  ...tseslint.configs.strictTypeChecked,
+  ...tseslint.configs.stylisticTypeChecked,
+
+  unicorn.configs['flat/recommended'],
+
+  prettier,
+
+  {
+    plugins: {
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-argument
+      import: fixupPluginRules(_import),
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+      'no-only-tests': noOnlyTests,
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+      'react-hooks': reactHooks,
+      'simple-import-sort': simpleImportSort,
+      'unused-imports': unusedImports,
+    },
+
+    languageOptions: {
+      ecmaVersion: 5,
+      sourceType: 'script',
+
+      parserOptions: {
+        projectService: true,
+      },
+    },
+
+    settings: {
+      react: {
+        version: 'detect',
+      },
+      formComponents: ['Form'],
+      linkComponents: [
+        { name: 'Link', linkAttribute: 'to' },
+        { name: 'NavLink', linkAttribute: 'to' },
+      ],
+    },
+
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+    rules: {
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
+      ...reactHooks.configs.recommended.rules,
+
+      'no-plusplus': 'error',
+      'object-shorthand': 'warn',
+      quotes: ['warn', 'single', { avoidEscape: true }],
+      'require-unicode-regexp': 'warn',
+
+      'import/first': 'warn',
+      'import/newline-after-import': 'warn',
+      'import/no-duplicates': 'warn',
+
+      'simple-import-sort/imports': 'warn',
+      'simple-import-sort/exports': 'warn',
+
+      'playwright/expect-expect': [
+        'warn',
+        {
+          assertFunctionNames: [
+            'expectAudioIsPlaying',
+            'expectAudioIsNotPlaying',
+            'expectAudioCurrentTimeToAlmostEqual',
+          ],
+        },
+      ],
+      'no-only-tests/no-only-tests': 'error',
+
+      '@typescript-eslint/no-unused-vars': 'off',
+      'unused-imports/no-unused-imports': 'warn',
+      'unused-imports/no-unused-vars': 'warn',
+
+      '@typescript-eslint/consistent-type-exports': 'warn',
+      '@typescript-eslint/consistent-type-imports': 'warn',
+      '@typescript-eslint/no-non-null-assertion': 'off', // Used for route params and in tests
+      '@typescript-eslint/only-throw-error': 'off', // Remix allows throwing `Response`s
+      '@typescript-eslint/prefer-promise-reject-errors': 'off',
+      '@typescript-eslint/restrict-template-expressions': [
+        'error',
+        {
+          allowAny: false,
+          allowBoolean: false,
+          allowNullish: false,
+          allowNumber: true,
+          allowRegExp: false,
+          allowNever: false,
+        },
+      ],
+      '@typescript-eslint/switch-exhaustiveness-check': [
+        'error',
+        {
+          allowDefaultCaseForExhaustiveSwitch: false,
+          requireDefaultForNonUnion: true,
+        },
+      ],
+
+      'unicorn/better-regex': 'off',
+      'unicorn/filename-case': 'off',
+      'unicorn/no-array-callback-reference': 'off',
+      'unicorn/no-null': 'off',
+      'unicorn/no-useless-undefined': 'off',
+      'unicorn/prefer-module': 'off',
+      'unicorn/prefer-switch': 'off',
+      'unicorn/prevent-abbreviations': 'off',
+      'unicorn/switch-case-braces': 'off',
+
+      'react/jsx-no-leaked-render': ['warn', { validStrategies: ['ternary'] }],
+    },
+  },
+  {
+    files: ['.eslintrc.cjs', 'stylelint.config.js', 'svgo.config.js'],
+
+    languageOptions: {
+      globals: globals.node,
+    },
+  },
+  {
+    files: ['playwright/**/*.ts', 'playwright/**/*.tsx'],
+
+    rules: {
+      'no-empty-pattern': 'off',
+      '@typescript-eslint/unbound-method': 'off',
+    },
+  },
+  includeIgnoreFile(gitignorePath),
+);