Upgrade eslint to v9

babel.config.js

@@ -1,4 +1,3 @@
-/* eslint-env node */
 const ENV = process.env.BABEL_ENV || process.env.NODE_ENV || 'development';
 
 let config = {

eslint.config.mjs

@@ -0,0 +1,81 @@
+import eslint from '@eslint/js';
+import { includeIgnoreFile } from '@eslint/compat';
+import path from 'node:path';
+
+import globals from 'globals';
+import reactPlugin from 'eslint-plugin-react';
+import reactHooksPlugin from 'eslint-plugin-react-hooks';
+import reactPerfPlugin from 'eslint-plugin-react-perf';
+import importPlugin from 'eslint-plugin-import';
+import prettierRecommended from 'eslint-plugin-prettier/recommended';
+
+const gitignorePath = path.resolve(import.meta.dirname, '.gitignore');
+
+/** @type {import('@typescript-eslint/utils').TSESLint.FlatConfig.ConfigFile} */
+export default [
+  includeIgnoreFile(gitignorePath),
+  {
+    name: 'global ignore',
+    // If ignores is used without any other keys in the configuration object,
+    // then the patterns act as global ignores.
+    ignores: []
+  },
+  eslint.configs.recommended,
+  reactPlugin.configs.flat.recommended,
+  importPlugin.flatConfigs.errors,
+  reactPerfPlugin.configs.flat['recommended'],
+  {
+    plugins: { 'react-hooks': reactHooksPlugin },
+    settings: {
+      // version config for eslint-plugin-react
+      react: {
+        version: 'detect'
+      }
+    }
+  },
+  prettierRecommended,
+  {
+    name: 'src and test rules',
+    files: ['packages/*/+(src|test)/**/*'],
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        process: 'readonly'
+      }
+    },
+    rules: {
+      'no-unused-vars': ['error', { ignoreRestSiblings: true }],
+      'no-console': 'error',
+      'react/prop-types': 'off',
+      'prefer-object-spread': 'warn',
+      'react-hooks/rules-of-hooks': 'error',
+      'react/jsx-no-constructed-context-values': 'error'
+    }
+  },
+  {
+    name: 'jest tests',
+    files: [`packages/*/test/**`],
+    languageOptions: {
+      globals: {
+        ...globals.jest,
+        ...globals.node
+      }
+    },
+    rules: {
+      'react/prop-types': 'off',
+      'react/display-name': 'off',
+      'react-perf/jsx-no-new-object-as-prop': 'off',
+      'react-perf/jsx-no-new-function-as-prop': 'off',
+      'react-perf/jsx-no-new-array-as-prop': 'off'
+    }
+  },
+  {
+    // rules for everybody else
+    ignores: [`packages/*/+(src|test)/**`],
+    languageOptions: {
+      globals: {
+        ...globals.node
+      }
+    }
+  }
+];