[ZEPPELIN-6425] Migrate zeppelin-react ESLint config to v9 flat format

zeppelin-web-angular/projects/zeppelin-react/README.md

@@ -58,7 +58,7 @@ From `projects/zeppelin-react/`, run `npm run build`. Output goes to `dist/`. In
 
 ## Linting
 
-From `projects/zeppelin-react/`, run `npm run lint` to check, `npm run lint:fix` to auto-fix. See `.eslintrc.json` for rules.
+From `projects/zeppelin-react/`, run `npm run lint` to check, `npm run lint:fix` to auto-fix. See `eslint.config.js` for rules.
 
 ## Project structure
 

zeppelin-web-angular/projects/zeppelin-react/eslint.config.js

@@ -0,0 +1,85 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// ESLint 9 flat config for the zeppelin-react sub-app (migrated from the
+// `.eslintrc.json` that worked under ESLint 8). The Angular 21 upgrade
+// (ZEPPELIN-6424) bumped the root install to ESLint 9, which dropped
+// `.eslintrc.*` support entirely; this file is a 1:1 port of the legacy rule
+// set so the React sources are still linted by `npm run lint:react`.
+//
+// The root `zeppelin-web-angular/eslint.config.js` ignores
+// `projects/zeppelin-react/**`, so this config owns linting inside this
+// directory exclusively.
+
+const js = require('@eslint/js');
+const globals = require('globals');
+const tseslint = require('typescript-eslint');
+const react = require('eslint-plugin-react');
+const reactHooks = require('eslint-plugin-react-hooks');
+
+module.exports = tseslint.config(
+  {
+    // == legacy `ignorePatterns`
+    ignores: ['dist/**', 'node_modules/**', 'webpack.config.js']
+  },
+  {
+    files: ['src/**/*.{ts,tsx}'],
+    // == legacy `extends`: eslint:recommended + @typescript-eslint/recommended
+    extends: [js.configs.recommended, ...tseslint.configs.recommended],
+    languageOptions: {
+      // == legacy `parserOptions`
+      parserOptions: {
+        ecmaFeatures: { jsx: true },
+        ecmaVersion: 'latest',
+        sourceType: 'module',
+        project: true,
+        tsconfigRootDir: __dirname
+      },
+      // == legacy `env: { browser: true, es2021: true }`
+      globals: {
+        ...globals.browser,
+        ...globals.es2021
+      }
+    },
+    plugins: {
+      react,
+      'react-hooks': reactHooks
+    },
+    settings: {
+      react: { version: 'detect' }
+    },
+    rules: {
+      // == legacy `plugin:react/recommended` + `plugin:react/jsx-runtime`
+      ...react.configs.recommended.rules,
+      ...react.configs['jsx-runtime'].rules,
+      // == legacy `plugin:react-hooks/recommended`
+      ...reactHooks.configs.recommended.rules,
+
+      // == legacy custom `rules` (1:1 port from .eslintrc.json)
+      '@typescript-eslint/no-explicit-any': 'error',
+      '@typescript-eslint/no-unused-vars': ['error', { argsIgnorePattern: '^_', varsIgnorePattern: '^_' }],
+      '@typescript-eslint/no-for-in-array': 'error',
+      '@typescript-eslint/no-this-alias': 'error',
+      'no-duplicate-imports': 'error',
+      'no-invalid-this': 'error',
+      'no-irregular-whitespace': 'error',
+      'no-param-reassign': 'error',
+      'no-redeclare': 'error',
+      'no-sparse-arrays': 'error',
+      'no-template-curly-in-string': 'error',
+      'prefer-object-spread': 'error',
+      'prefer-template': 'error',
+      yoda: 'error',
+      'react-hooks/exhaustive-deps': 'error'
+    }
+  }
+);