chore: add ESLint configuration to catch code quality issues

.changeset/add-eslint-configuration.md

@@ -0,0 +1,12 @@
+---
+---
+
+Add ESLint configuration for code quality and consistency
+
+Adds repository-wide ESLint configuration to catch common code quality issues. This is a development-only change that adds linting tooling without affecting any package functionality or APIs.
+
+**Configuration includes:**
+- TypeScript-specific rules for type safety and promise handling
+- Basic JavaScript rules for code consistency
+- Lenient rules for test files
+- Integration with lint-staged for pre-commit linting

.eslintrc.js

@@ -0,0 +1,93 @@
+module.exports = {
+  root: true,
+  env: {
+    node: true,
+    es6: true,
+  },
+  plugins: ['@typescript-eslint', 'jest'],
+  extends: ['eslint:recommended', 'plugin:jest/recommended'],
+  rules: {
+    // Best practices
+    'no-console': 'off', // CLI tool, console is expected
+    'prefer-const': 'error',
+    'no-var': 'error',
+
+    // Jest best practices
+    'jest/expect-expect': 'warn',
+    'jest/no-disabled-tests': 'warn',
+    'jest/no-focused-tests': 'error',
+  },
+  overrides: [
+    {
+      // TypeScript files with type checking
+      files: ['**/*.ts', '**/*.tsx'],
+      parser: '@typescript-eslint/parser',
+      parserOptions: {
+        ecmaVersion: 2018,
+        sourceType: 'module',
+        project: ['./tsconfig.base.json', './packages/*/tsconfig.json'],
+        tsconfigRootDir: __dirname,
+      },
+      extends: [
+        'eslint:recommended',
+        'plugin:@typescript-eslint/recommended',
+        'plugin:@typescript-eslint/recommended-requiring-type-checking',
+        'plugin:jest/recommended',
+      ],
+      rules: {
+        // Catch implicit any (would catch Issue #1)
+        '@typescript-eslint/no-explicit-any': 'warn', // Warn, not error (any is sometimes needed)
+        '@typescript-eslint/no-unsafe-assignment': 'warn',
+        '@typescript-eslint/no-unsafe-member-access': 'warn',
+        '@typescript-eslint/no-unsafe-call': 'warn',
+
+        // Catch promise issues
+        '@typescript-eslint/no-floating-promises': 'error',
+        '@typescript-eslint/no-misused-promises': 'error',
+
+        // General code quality
+        '@typescript-eslint/no-unused-vars': [
+          'error',
+          {
+            argsIgnorePattern: '^_',
+            varsIgnorePattern: '^_',
+          },
+        ],
+
+        // Best practices
+        'no-console': 'off',
+        'prefer-const': 'error',
+        'no-var': 'error',
+
+        // Jest best practices
+        'jest/expect-expect': 'warn',
+        'jest/no-disabled-tests': 'warn',
+        'jest/no-focused-tests': 'error',
+      },
+    },
+    {
+      // More lenient rules for test files
+      files: ['**/__tests__/**', '**/*.test.ts', '**/*.test.js'],
+      env: {
+        jest: true,
+      },
+      rules: {
+        '@typescript-eslint/no-explicit-any': 'off',
+        '@typescript-eslint/no-unsafe-assignment': 'off',
+        '@typescript-eslint/no-unsafe-member-access': 'off',
+        '@typescript-eslint/no-unsafe-call': 'off',
+      },
+    },
+  ],
+  ignorePatterns: [
+    'node_modules/',
+    'dist/',
+    'build/',
+    'coverage/',
+    '*.config.js',
+    '.eslintrc.js',
+    'jest.config.js',
+    'jest.config.base.js',
+    '.changeset/',
+  ],
+};

package.json

@@ -19,7 +19,9 @@
     "docs": "npm run docs --workspaces --if-present",
     "prepare": "husky install",
     "pre-commit": "lint-staged",
-    "reset": "npm exec --workspaces -- npx rimraf node_modules && npx rimraf node_modules"
+    "reset": "npm exec --workspaces -- npx rimraf node_modules && npx rimraf node_modules",
+    "lint": "eslint . --ext .ts,.js,.tsx,.jsx",
+    "lint:fix": "eslint . --ext .ts,.js,.tsx,.jsx --fix"
   },
   "devDependencies": {
     "@changesets/changelog-github": "^0.4.8",
@@ -28,11 +30,15 @@
     "@commitlint/config-conventional": "^19.1.0",
     "@twilio/test-dep": "npm:twilio@4.22.0",
     "@types/jest": "^29.2.4",
+    "@typescript-eslint/eslint-plugin": "^6.21.0",
+    "@typescript-eslint/parser": "^6.21.0",
     "all-contributors-cli": "^6.1.2",
     "commitizen": "^4.2.4",
     "commitlint-plugin-workspace-scopes": "^1.1.0",
     "conventional-changelog-cli": "^2.1.0",
     "cz-conventional-changelog": "^2.1.0",
+    "eslint": "^8.57.1",
+    "eslint-plugin-jest": "^27.9.0",
     "husky": "^8.0.2",
     "jest": "^29.7.0",
     "jest-express": "^1.10.1",
@@ -47,6 +53,7 @@
   },
   "lint-staged": {
     "*.{js,jsx,ts,tsx}": [
+      "eslint --fix",
       "prettier --write",
       "git add"
     ]