Error Handling Expert Skill Skill

Error Handling Expert Skill

Expert in error handling patterns, exception management, error responses, logging, and error recovery strategies for React, Next.js, and NestJS applications.

When to Use

Implementing error handling
Creating exception filters
Designing error responses
Setting up error logging
Implementing error recovery
Handling async errors
Creating error boundaries
Implementing retry logic

Project Context Discovery

Before providing guidance:

Check .agents/SYSTEM/ARCHITECTURE.md for error patterns
Review existing exception filters
Check for error monitoring (Sentry, Rollbar)
Review logging libraries (Winston, Pino)

Core Principles

Error Types

Application Errors: 400, 401, 403, 404, 409, 422 System Errors: 500, 502, 503, 504

Error Response Format

{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Validation failed",
    "details": [...],
    "timestamp": "2025-01-01T00:00:00Z",
    "path": "/api/users",
    "requestId": "req-123456"
  }
}

Quick Patterns

NestJS Exception Filter

@Catch()
export class AllExceptionsFilter implements ExceptionFilter {
  catch(exception: unknown, host: ArgumentsHost) {
    // Log, format, respond
  }
}

React Error Boundary

class ErrorBoundary extends React.Component {
  componentDidCatch(error, errorInfo) {
    // Log to monitoring
  }
}

Retry with Backoff

async function retryWithBackoff<T>(fn, maxRetries = 3): Promise<T>

Best Practices

User-friendly messages, no sensitive info
Log all errors with context
Integrate error monitoring (Sentry)
Implement retry logic and circuit breakers
Provide fallback values
Test error cases

Recovery Strategies

Retry Logic - Exponential backoff
Circuit Breaker - Prevent cascade failures
Fallback Values - Graceful degradation

For complete exception filter implementations, custom exceptions, validation pipe setup, error boundaries, circuit breaker pattern, logging integration, and database/API error patterns, see: references/full-guide.md

Agent Skills: Error Handling Expert Skill

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