Switch to ESLint v9

eslint.config.mjs

@@ -0,0 +1,74 @@
+import typescriptEslint from '@typescript-eslint/eslint-plugin';
+import globals from 'globals';
+import tsParser from '@typescript-eslint/parser';
+import parser from 'svelte-eslint-parser';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import js from '@eslint/js';
+import { FlatCompat } from '@eslint/eslintrc';
+
+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: [
+      '**/.DS_Store',
+      '**/node_modules',
+      'build',
+      '.svelte-kit',
+      'package',
+      '**/.env',
+      '**/.env.*',
+      '!**/.env.example',
+      '**/pnpm-lock.yaml',
+      '**/package-lock.json',
+      '**/yarn.lock',
+      '**/.fonts'
+    ]
+  },
+  ...compat.extends(
+    'eslint:recommended',
+    'plugin:@typescript-eslint/recommended',
+    'plugin:svelte/recommended',
+    'prettier'
+  ),
+  {
+    plugins: {
+      '@typescript-eslint': typescriptEslint
+    },
+
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        ...globals.node
+      },
+
+      parser: tsParser,
+      ecmaVersion: 2020,
+      sourceType: 'module',
+
+      parserOptions: {
+        extraFileExtensions: ['.svelte']
+      }
+    }
+  },
+  {
+    files: ['**/*.svelte'],
+
+    languageOptions: {
+      parser: parser,
+      ecmaVersion: 5,
+      sourceType: 'script',
+
+      parserOptions: {
+        parser: '@typescript-eslint/parser'
+      }
+    }
+  }
+];

package.json

@@ -12,15 +12,18 @@
     "format": "prettier --write ."
   },
   "devDependencies": {
+    "@eslint/eslintrc": "^3.1.0",
+    "@eslint/js": "^9.13.0",
     "@sveltejs/adapter-cloudflare": "^4.7.4",
     "@sveltejs/enhanced-img": "^0.3.10",
     "@sveltejs/kit": "^2.7.3",
     "@sveltejs/vite-plugin-svelte": "^4.0.0",
-    "@typescript-eslint/eslint-plugin": "^6.21.0",
-    "@typescript-eslint/parser": "^6.21.0",
-    "eslint": "^8.57.1",
+    "@typescript-eslint/eslint-plugin": "^8.11.0",
+    "@typescript-eslint/parser": "^8.11.0",
+    "eslint": "^9.13.0",
     "eslint-config-prettier": "^9.1.0",
     "eslint-plugin-svelte": "^2.46.0",
+    "globals": "^15.11.0",
     "lightningcss": "^1.27.0",
     "prettier": "^3.3.3",
     "prettier-plugin-svelte": "^3.2.7",