chore: update to eslint v9

eslint.config.mjs

@@ -0,0 +1,124 @@
+import { defineConfig, globalIgnores } from 'eslint/config';
+import react from 'eslint-plugin-react';
+// import eslintPluginPrettierRecommended from 'eslint-plugin-prettier/recommended';
+import globals from 'globals';
+// import babelParser from '@babel/eslint-parser';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import json from '@eslint/json';
+import js from '@eslint/js';
+import stylisticJs from '@stylistic/eslint-plugin-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 defineConfig([
+  // ignoring for now, many unformatted files
+  // eslintPluginPrettierRecommended,
+  {
+    plugins: {
+      json,
+      '@stylistic/js': stylisticJs,
+    },
+  },
+  {
+    files: ['**/*.json'],
+    language: 'json/json',
+    rules: {
+      'json/no-duplicate-keys': 'error',
+    },
+  },
+
+  {
+    files: ['**/*.js'],
+    plugins: {
+      js,
+    },
+    extends: ['js/recommended'],
+    rules: {
+      'no-unused-vars': 'warn',
+      'no-undef': 'warn',
+    },
+  },
+  {
+    files: ['**/*.{js,jsx,mjs,cjs,ts,tsx}'],
+    plugins: {
+      react,
+    },
+    languageOptions: {
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+      globals: {
+        ...globals.browser, // causes error
+        ...globals.node,
+        ...globals.commonjs,
+      },
+    },
+    settings: {
+      react: {
+        version: 'detect',
+      },
+    },
+    rules: {
+      'no-async-promise-executor': 'off',
+      'react/jsx-uses-react': 'error',
+      'react/jsx-uses-vars': 'error',
+      'react/prop-types': 'off',
+      // ignoring for now, many long lines
+      // '@stylistic/js/max-len': ['error', { code: 100 }],
+    },
+  },
+  {
+    files: ['test/**/*.{js,mjs,cjs,ts}'],
+    languageOptions: {
+      globals: {
+        ...globals.mocha,
+      },
+    },
+  },
+  //   {
+  //     extends: compat.extends('prettier', 'plugin:json/recommended'),
+
+  //     plugins: {
+  //       react,
+  //       prettier,
+  //     },
+
+  //     languageOptions: {
+  //       globals: {
+  //         ...globals.node,
+  //         // causes error:
+  //         // TypeError: Key "languageOptions": Key "globals": Global "AudioWorkletGlobalScope " has leading or trailing whitespace.
+  //         // ...globals.browser,
+  //         ...globals.commonjs,
+  //         ...globals.mocha,
+  //       },
+
+  //       parser: babelParser,
+  //       ecmaVersion: 12,
+  //       sourceType: 'module',
+
+  //       parserOptions: {
+  //         requireConfigFile: false,
+
+  //         ecmaFeatures: {
+  //           jsx: true,
+  //           modules: true,
+  //         },
+
+  //         babelOptions: {
+  //           presets: ['@babel/preset-react'],
+  //         },
+  //       },
+  //     },
+  //   },
+]);