Production Code Standards Skill

Overview

This skill encapsulates the CLAUDE Framework standards for production-ready code development. It ensures consistency, quality, security, and maintainability across all code deliverables.

When to Use This Skill

• Creating new features requiring production quality
• Code reviews against production standards
• Refactoring legacy code to modern standards
• Training on development best practices
• Pre-deployment quality validation

Core Principles (Level 1 - Always Loaded)

🎯 Priority Rules (CRITICAL - Non-Negotiable)

Basis Missie - Breaking these = delivery rejected:

• BM-1 (MUST): Never invent, omit, or skip functionality
• BM-2 (MUST): Follow exact instructions from user
• BM-3 (MUST): Ask questions when unclear, never assume

Impact Analysis - Before ANY code change:

• IA-1 (MUST): Analyze impact on existing functionality
• IA-2 (MUST): Check all dependencies that will be affected
• IA-3 (MUST): Search for all files that import/use the code
• IA-4 (MUST): Run existing tests BEFORE changes
• IA-5 (MUST): Backup/document original implementation when overwriting
• IA-6 (MUST NOT): Never overwrite code without impact check
• IA-7 (MUST): Ask permission before overwriting with impact explanation

🔴 Code Quality Standards

Single Responsibility & DRY:

// ✅ GOOD - Single responsibility
class UserAuthenticator {
  authenticate(credentials: Credentials): AuthResult {
    return this.validateAndAuthenticate(credentials);
  }
}

class UserNotifier {
  sendWelcomeEmail(user: User): void {
    this.emailService.send(user.email, 'Welcome!');
  }
}

// ❌ BAD - Multiple responsibilities
class UserManager {
  authenticate() { /* auth logic */ }
  sendEmail() { /* email logic */ }
  updateDatabase() { /* db logic */ }
}

Naming Conventions (MUST):

• Functions: getUserData(), calculateTotal() (verbs)
• Variables: user, totalAmount (nouns)
• Booleans: isValid, hasPermission (is/has prefix)
• Constants: MAX_RETRY_COUNT, API_BASE_URL
• Classes: UserService, OrderController (PascalCase)

Function Size Limit:

• Maximum 20 lines per function
• Extract complex logic into helper functions
• One level of abstraction per function

🔒 Error Handling (CRITICAL)

// ✅ GOOD - Comprehensive error handling
async function fetchUserData(userId: string): Promise<User> {
  try {
    if (!userId || userId.trim() === '') {
      throw new ValidationError('User ID is required');
    }

    const user = await db.users.findById(userId);

    if (!user) {
      throw new NotFoundError(`User ${userId} not found`);
    }

    logger.info('User fetched successfully', { userId });
    return user;

  } catch (error) {
    if (error instanceof ValidationError || error instanceof NotFoundError) {
      throw error;
    }

    logger.error('Failed to fetch user', { userId, error: error.message });
    throw new DatabaseError('Failed to fetch user data');
  }
}

// ❌ BAD - Silent failure
async function fetchUserData(userId: string) {
  try {
    return await db.users.findById(userId);
  } catch (error) {
    return null; // Silent failure - NEVER do this!
  }
}

Error Handling Rules (MUST):

• Handle all error scenarios explicitly
• Use specific error types/messages
• Log errors with context
• Never silent failures
• Fail fast: validate inputs early

🧪 TDD Requirements (MUST)

Red-Green-Refactor Cycle:

1. Red: Write failing test first
2. Green: Write minimal code to pass
3. Refactor: Improve code quality

Test Coverage Requirements:

• Minimum 80% coverage for new code
• Test happy path, errors, edge cases
• Arrange-Act-Assert pattern
• Descriptive test names

// ✅ GOOD - Descriptive test with AAA pattern
describe('UserAuthenticator', () => {
  it('should return success when valid credentials provided', () => {
    // Arrange
    const authenticator = new UserAuthenticator();
    const validCredentials = { email: 'test@example.com', password: 'Valid123!' };

    // Act
    const result = authenticator.authenticate(validCredentials);

    // Assert
    expect(result.success).toBe(true);
    expect(result.user).toBeDefined();
  });

  it('should throw ValidationError when email is missing', () => {
    // Arrange
    const authenticator = new UserAuthenticator();
    const invalidCredentials = { email: '', password: 'Valid123!' };

    // Act & Assert
    expect(() => authenticator.authenticate(invalidCredentials))
      .toThrow(ValidationError);
  });
});

🔐 Security Rules (CRITICAL)

Input Validation (MUST):

// ✅ GOOD - Validate at boundaries
function createUser(input: unknown): User {
  const validated = userSchema.parse(input); // Zod/Joi validation

  // Sanitize
  const sanitized = {
    email: validator.normalizeEmail(validated.email),
    name: validator.escape(validated.name),
  };

  return userService.create(sanitized);
}

// ❌ BAD - No validation
function createUser(input: any) {
  return userService.create(input); // Unsafe!
}

Security Requirements (MUST):

• Input validation at system boundaries
• Output sanitization
• Secrets via env vars/vault (never hardcoded)
• Never log sensitive data (passwords, tokens, PII)
• TLS everywhere, HSTS, secure cookies
• Dependency scanning enabled

Detailed Patterns (Level 2 - Load on Request)

See companion files:

• detailed-patterns.md - Advanced patterns and examples
• refactoring-guide.md - Step-by-step refactoring strategies
• security-checklist.md - Comprehensive security validation

Automation Tools (Level 3 - Load When Needed)

See scripts directory:

• scripts/pre-commit-check.sh - Run before commits
• scripts/quality-gate.sh - CI/CD quality validation
• scripts/security-scan.sh - Dependency and secret scanning

Quick Reference Checklist

Before marking any task complete:

• All MUST rules followed
• Impact analysis completed
• Tests written first (TDD)
• 80%+ test coverage
• All error scenarios handled
• Security validation passed
• No hardcoded secrets
• Functions under 20 lines
• Descriptive naming used
• Code reviewed

Integration with Agents

senior-fullstack-developer:

• Primary agent for implementing these standards
• Uses this skill for all production code
• References detailed patterns for complex scenarios

code-refactoring-specialist:

• Uses this skill when modernizing legacy code
• Applies standards during refactoring
• Validates against quality checklist

qa-testing-engineer:

• Uses this skill to validate test coverage
• Ensures TDD compliance
• Reviews test quality against standards

Success Metrics

Track these KPIs:

• First-time success rate > 70%
• Average iterations < 3
• Test coverage > 80%
• Security issues: 0
• Production bugs < 2/week

Version 1.0.0 | Compatible with CLAUDE Framework v5.0