Configure linter + prettier.

- This is based on existing expectations for TS code in Google-esc repos.
- First part of the change (we have not run any linter or formatting commands). After this changeset goes in I'll do a mass changeset push.

Fixes https://b.corp.google.com/issues/411384603

1 files changed, 131 insertions, 0 deletions

diff --git a/eslint.config.js b/eslint.config.js
new file mode 100644
index 00000000..32f4c364
--- /dev/null
+++ b/eslint.config.js
@@ -0,0 +1,131 @@
+import eslint from '@eslint/js';
+import tseslint from 'typescript-eslint';
+import reactPlugin from 'eslint-plugin-react';
+import reactRecommended from 'eslint-plugin-react/configs/recommended.js';
+import reactHooks from 'eslint-plugin-react-hooks';
+import prettierConfig from 'eslint-config-prettier';
+import importPlugin from 'eslint-plugin-import';
+import globals from 'globals';
+
+export default tseslint.config(
+  {
+    // Global ignores
+    ignores: ['node_modules/**', 'eslint.config.js', 'packages/cli/dist/**'],
+  },
+  eslint.configs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    // React specific config
+    files: ['packages/cli/src/**/*.tsx'], // Target only TSX in the cli package
+    languageOptions: {
+      // Keep languageOptions from reactRecommended if needed, or define explicitly
+      parserOptions: {
+        ecmaFeatures: { jsx: true },
+      },
+      globals: {
+        ...globals.browser,
+      },
+    },
+    plugins: {
+      // Define the plugins used in this block
+      react: reactPlugin,
+      'react-hooks': reactHooks,
+    },
+    rules: {
+      // Apply recommended rules explicitly
+      ...reactRecommended.rules,
+      ...reactHooks.configs.recommended.rules,
+      // Custom overrides
+      'react/react-in-jsx-scope': 'off',
+      'react/prop-types': 'off',
+    },
+    settings: {
+      react: {
+        version: 'detect',
+      },
+    },
+  },
+  {
+    // Import specific config
+    files: ['packages/cli/src/**/*.{ts,tsx}'], // Target only TS/TSX in the cli package
+    plugins: {
+      import: importPlugin,
+    },
+    settings: {
+      'import/resolver': {
+        typescript: true,
+        node: true,
+      },
+    },
+    rules: {
+      ...importPlugin.configs.recommended.rules,
+      ...importPlugin.configs.typescript.rules,
+      'import/no-default-export': 'warn',
+      'import/no-unresolved': 'off', // Disable for now, can be noisy with monorepos/paths
+    },
+  },
+  {
+    // General overrides and rules for the project (TS/TSX files)
+    files: ['packages/cli/src/**/*.{ts,tsx}'], // Target only TS/TSX in the cli package
+    languageOptions: {
+      globals: {
+        ...globals.node,
+        ...globals.es2021,
+      },
+    },
+    rules: {
+      // General Best Practice Rules (subset adapted for flat config)
+      '@typescript-eslint/array-type': ['error', { default: 'array-simple' }],
+      'arrow-body-style': ['error', 'as-needed'],
+      curly: ['error', 'multi-line'],
+      eqeqeq: ['error', 'always', { null: 'ignore' }],
+      '@typescript-eslint/consistent-type-assertions': [
+        'error',
+        { assertionStyle: 'as' },
+      ],
+      '@typescript-eslint/explicit-member-accessibility': [
+        'error',
+        { accessibility: 'no-public' },
+      ],
+      '@typescript-eslint/no-explicit-any': 'warn',
+      '@typescript-eslint/no-inferrable-types': [
+        'error',
+        { ignoreParameters: true, ignoreProperties: true },
+      ],
+      '@typescript-eslint/no-namespace': ['error', { allowDeclarations: true }],
+      '@typescript-eslint/no-unused-vars': [
+        'warn',
+        { argsIgnorePattern: '^_', varsIgnorePattern: '^_', caughtErrorsIgnorePattern: '^_' },
+      ],
+      'no-cond-assign': 'error',
+      'no-debugger': 'error',
+      'no-duplicate-case': 'error',
+      'no-restricted-syntax': [
+        'error',
+        {
+          selector: 'CallExpression[callee.name="require"]',
+          message: 'Avoid using require(). Use ES6 imports instead.',
+        },
+        {
+          selector: 'ThrowStatement > Literal:not([value=/^\\w+Error:/])',
+          message: 'Do not throw string literals or non-Error objects. Throw new Error("...") instead.',
+        },
+      ],
+      'no-unsafe-finally': 'error',
+      'no-unused-expressions': 'off', // Disable base rule
+      '@typescript-eslint/no-unused-expressions': [ // Enable TS version
+        'error',
+        { allowShortCircuit: true, allowTernary: true },
+      ],
+      'no-var': 'error',
+      'object-shorthand': 'error',
+      'one-var': ['error', 'never'],
+      'prefer-arrow-callback': 'error',
+      'prefer-const': ['error', { destructuring: 'all' }],
+      radix: 'error',
+      'default-case': 'error',
+    },
+  },
+  // Prettier config must be last
+  prettierConfig,
+);