🧵 Migrate to v9 ESLint and new flat config system

eslint.config.mjs

@@ -0,0 +1,51 @@
+import js from '@eslint/js'
+import tseslint from 'typescript-eslint'
+import globals from 'globals'
+
+export default [
+  // Apply recommended rules for JavaScript and TypeScript
+  js.configs.recommended,
+  ...tseslint.configs.recommended,
+
+  // Customize rules & options
+  {
+    languageOptions: {
+      globals: {
+        // Add browser globals like `window`, `document`, etc.
+        ...globals.browser,
+      },
+    },
+
+    rules: {
+      'no-var': 'error',
+      'prefer-const': 'error',
+      'no-unused-vars': 'off',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        {
+          // Allows for Go style _var ignoring
+          varsIgnorePattern: '^_',
+          argsIgnorePattern: '^_',
+          caughtErrorsIgnorePattern: '^_',
+        },
+      ],
+      'no-undef': 'error',
+      'no-duplicate-imports': 'error',
+      'no-constructor-return': 'error',
+      'no-promise-executor-return': 'error',
+      'prefer-template': 'error',
+      'dot-notation': 'error',
+
+      'func-style': [
+        'error',
+        'declaration',
+        {
+          allowArrowFunctions: true,
+        },
+      ],
+
+      'object-shorthand': 'error',
+      'spaced-comment': 'error',
+    },
+  },
+]