feat: add comprehensive NodeJS development skills and rules
Based on Planner and Memory Manager analysis: New Skills (8): - nodejs-express-patterns: App structure, routing, middleware - nodejs-security-owasp: OWASP Top 10 security practices - nodejs-testing-jest: Unit/integration tests, mocking - nodejs-auth-jwt: JWT authentication, OAuth, sessions - nodejs-error-handling: Error classes, middleware, async handlers - nodejs-middleware-patterns: Auth, validation, rate limiting - nodejs-db-patterns: SQLite, PostgreSQL, MongoDB patterns - nodejs-npm-management: package.json, scripts, dependencies New Rules: - nodejs.md: Code style, security, best practices Updated: - backend-developer.md: Added skills reference table Milestone: #48 NodeJS Development Coverage Related: Planner & Memory Manager analysis results
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.kilo/skills/nodejs-error-handling/SKILL.md
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.kilo/skills/nodejs-error-handling/SKILL.md
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# NodeJS Error Handling
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Comprehensive error handling patterns for Node.js applications.
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## Error Classes
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```javascript
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// src/utils/AppError.js
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class AppError extends Error {
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constructor(message, statusCode) {
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super(message);
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this.statusCode = statusCode;
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this.status = `${statusCode}`.startsWith('4') ? 'fail' : 'error';
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this.isOperational = true;
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Error.captureStackTrace(this, this.constructor);
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}
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}
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class NotFoundError extends AppError {
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constructor(resource = 'Resource') {
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super(`${resource} not found`, 404);
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}
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}
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class ValidationError extends AppError {
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constructor(errors) {
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super('Validation failed', 400);
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this.errors = errors;
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}
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}
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class UnauthorizedError extends AppError {
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constructor(message = 'Unauthorized') {
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super(message, 401);
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}
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}
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class ForbiddenError extends AppError {
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constructor(message = 'Forbidden') {
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super(message, 403);
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}
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}
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class ConflictError extends AppError {
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constructor(message = 'Conflict') {
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super(message, 409);
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}
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}
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module.exports = {
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AppError,
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NotFoundError,
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ValidationError,
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UnauthorizedError,
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ForbiddenError,
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ConflictError
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};
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```
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## Error Middleware
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```javascript
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// src/middleware/error.js
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const AppError = require('../utils/AppError');
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// Not found handler
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function notFoundHandler(req, res, next) {
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next(new AppError(`Cannot find ${req.originalUrl} on this server`, 404));
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}
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// Global error handler
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function errorHandler(err, req, res, next) {
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err.statusCode = err.statusCode || 500;
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err.status = err.status || 'error';
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if (process.env.NODE_ENV === 'development') {
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sendErrorDev(err, res);
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} else {
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sendErrorProd(err, res);
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}
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}
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function sendErrorDev(err, res) {
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res.status(err.statusCode).json({
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status: err.status,
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message: err.message,
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stack: err.stack,
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error: err
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});
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}
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function sendErrorProd(err, res) {
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// Operational error: send message to client
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if (err.isOperational) {
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res.status(err.statusCode).json({
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status: err.status,
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message: err.message
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});
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} else {
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// Programming error: don't leak details
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console.error('ERROR:', err);
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res.status(500).json({
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status: 'error',
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message: 'Something went wrong'
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});
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}
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}
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module.exports = { notFoundHandler, errorHandler };
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```
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## Async Error Wrapper
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```javascript
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// src/middleware/asyncHandler.js
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function asyncHandler(fn) {
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return (req, res, next) => {
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Promise.resolve(fn(req, res, next)).catch(next);
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};
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}
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// Usage
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router.get('/users/:id', asyncHandler(controller.getById));
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// Or wrap entire controller
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const wrapController = (controller) => {
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const wrapped = {};
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for (const [key, fn] of Object.entries(controller)) {
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wrapped[key] = asyncHandler(fn.bind(controller));
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}
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return wrapped;
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};
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module.exports = { asyncHandler, wrapController };
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```
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## Validation Errors
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```javascript
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// src/middleware/validation.js
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const { validationResult } = require('express-validator');
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const { ValidationError } = require('../utils/AppError');
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function validate(validations) {
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return async (req, res, next) => {
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await Promise.all(validations.map(validation => validation.run(req)));
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const errors = validationResult(req);
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if (errors.isEmpty()) {
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return next();
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}
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const extractedErrors = errors.array().map(err => ({
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field: err.path,
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message: err.msg,
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value: err.value
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}));
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return next(new ValidationError(extractedErrors));
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};
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}
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module.exports = { validate };
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```
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## Database Error Handling
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```javascript
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// src/middleware/dbErrorHandler.js
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const AppError = require('../utils/AppError');
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function dbErrorHandler(err, req, res, next) {
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// PostgreSQL unique violation
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if (err.code === '23505') {
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const field = err.constraint.split('_')[0];
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return next(new AppError(`${field} already exists`, 409));
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}
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// PostgreSQL foreign key violation
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if (err.code === '23503') {
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return next(new AppError('Referenced resource not found', 400));
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}
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// SQLite unique violation
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if (err.code === 'SQLITE_CONSTRAINT_UNIQUE') {
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return next(new AppError('Resource already exists', 409));
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}
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// MongoDB duplicate key
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if (err.code === 11000) {
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const field = Object.keys(err.keyValue)[0];
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return next(new AppError(`${field} already exists`, 409));
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}
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// MongoDB validation error
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if (err.name === 'ValidationError') {
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const messages = Object.values(err.errors).map(e => e.message);
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return next(new AppError(messages.join('. '), 400));
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}
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// MongoDB cast error
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if (err.name === 'CastError') {
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return next(new AppError('Invalid ID format', 400));
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}
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next(err);
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}
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module.exports = dbErrorHandler;
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```
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## Logging Errors
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```javascript
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// src/utils/logger.js
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const pino = require('pino');
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const logger = pino({
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level: process.env.LOG_LEVEL || 'info',
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transport: process.env.NODE_ENV === 'development'
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? { target: 'pino-pretty' }
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: undefined
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});
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function logError(err, req = null) {
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logger.error({
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message: err.message,
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stack: err.stack,
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statusCode: err.statusCode || 500,
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path: req?.path,
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method: req?.method,
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user: req?.user?.id,
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body: req?.body,
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query: req?.query,
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params: req?.params,
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timestamp: new Date().toISOString()
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});
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}
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function logInfo(message, data = {}) {
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logger.info({ message, ...data });
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}
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module.exports = { logger, logError, logInfo };
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```
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## Unhandled Rejections
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```javascript
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// src/server.js
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process.on('unhandledRejection', (err) => {
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console.error('UNHANDLED REJECTION:', err);
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logError(err);
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// Graceful shutdown
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server.close(() => {
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process.exit(1);
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});
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});
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process.on('uncaughtException', (err) => {
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console.error('UNCAUGHT EXCEPTION:', err);
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logError(err);
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// Must exit immediately for uncaught exceptions
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process.exit(1);
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});
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```
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## API Error Responses
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```javascript
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// Standardized error responses
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const errorResponses = {
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400: {
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status: 'fail',
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message: 'Bad Request',
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errors: []
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},
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401: {
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status: 'fail',
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message: 'Unauthorized'
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},
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403: {
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status: 'fail',
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message: 'Forbidden'
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},
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404: {
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status: 'fail',
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message: 'Not Found'
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},
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409: {
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status: 'fail',
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message: 'Conflict'
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},
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500: {
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status: 'error',
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message: 'Internal Server Error'
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}
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};
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// Example responses
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{
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"status": "fail",
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"message": "Validation failed",
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"errors": [
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{ "field": "email", "message": "Invalid email format" },
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{ "field": "password", "message": "Must be at least 8 characters" }
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]
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}
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```
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## Error Handling in Tests
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```javascript
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// tests/unit/errors.test.js
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describe('Error Handling', () => {
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it('should handle AppError', () => {
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const error = new AppError('Test error', 400);
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expect(error.statusCode).toBe(400);
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expect(error.status).toBe('fail');
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expect(error.isOperational).toBe(true);
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});
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it('should handle async errors', async () => {
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const req = {};
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const res = {};
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const next = jest.fn();
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const handler = asyncHandler(async () => {
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throw new AppError('Test', 400);
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});
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await handler(req, res, next);
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expect(next).toHaveBeenCalledWith(expect.any(AppError));
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});
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});
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```
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