Golang Clean Architecture

Audit Go services for Clean Architecture compliance. Ensures proper layering, dependency rules, and separation of concerns in gRPC → Usecase → Repository → Domain architectures.

When to Apply

Use this skill when:

• Auditing service architecture
• Reviewing new features for layer violations
• Refactoring toward Clean Architecture
• Code review for dependency rules
• Planning service structure
• Migrating to layered architecture
• Ensuring testability through dependency injection

Architecture Layers

┌─────────────────────────────────────┐
│  Delivery (gRPC/HTTP/GraphQL)       │ ← Thin, no business logic
├─────────────────────────────────────┤
│  Usecase (Business Logic)           │ ← Orchestration
├─────────────────────────────────────┤
│  Repository (Data Access)           │ ← CRUD only
├─────────────────────────────────────┤
│  Domain (Entities/Interfaces)       │ ← Pure business logic
└─────────────────────────────────────┘

Dependency Rule: Dependencies point INWARD only (toward domain).

Rules Covered (9 total)

High-Impact Patterns (4)

• high-business-logic-handler - Keep delivery layer thin
• high-business-logic-repository - No business logic in data layer
• high-constructor-creates-deps - Inject dependencies, don't create
• high-transaction-in-repository - Transactions belong in usecase

Architecture Rules (5)

• arch-domain-import-infra - Domain must not import infrastructure
• arch-concrete-dependency - Depend on interfaces, not concrete types
• arch-repository-business-logic - Repositories do CRUD only
• arch-usecase-orchestration - Usecases orchestrate, entities decide
• arch-interface-segregation - Small, consumer-defined interfaces

Common Violations

❌ Business Logic in Handler

// gRPC handler doing calculations
func (h *Handler) CreateOrder(ctx context.Context, req *pb.Request) (*pb.Response, error) {
    total := req.Price * req.Quantity // BAD: calculation in handler
    discount := total * 0.1           // BAD: business rules in delivery layer
    
    order := &domain.Order{
        Total: total - discount,
    }
    return h.orderRepo.Save(ctx, order)
}

✅ Business Logic in Usecase

// Handler delegates to usecase
func (h *Handler) CreateOrder(ctx context.Context, req *pb.Request) (*pb.Response, error) {
    order, err := h.orderUsecase.Create(ctx, req.Price, req.Quantity)
    if err != nil {
        return nil, err
    }
    return &pb.Response{OrderId: order.ID}, nil
}

// Usecase contains business logic
func (u *OrderUsecase) Create(ctx context.Context, price, quantity int) (*domain.Order, error) {
    total := price * quantity      // GOOD: calculation in usecase
    discount := total * 0.1        // GOOD: business rules in usecase
    
    order := &domain.Order{
        Total: total - discount,
    }
    return u.orderRepo.Save(ctx, order)
}

❌ Repository with Business Logic

// Repository doing validation and business rules
func (r *OrderRepo) Save(ctx context.Context, order *domain.Order) error {
    if order.Total < 0 {                    // BAD: validation in repository
        return errors.New("invalid total")
    }
    if order.Total > 1000000 {              // BAD: business rule in repository
        order.Status = "needs_approval"     // BAD: state change in repository
    }
    return r.db.Create(order)
}

✅ Repository Does CRUD Only

// Repository only handles data persistence
func (r *OrderRepo) Save(ctx context.Context, order *domain.Order) error {
    return r.db.Create(order) // GOOD: simple CRUD
}

// Validation happens in usecase or domain entity
func (u *OrderUsecase) Create(ctx context.Context, price, quantity int) (*domain.Order, error) {
    order := domain.NewOrder(price, quantity) // Entity validates itself
    if err := order.Validate(); err != nil {    // GOOD: validation in domain
        return nil, err
    }
    if order.NeedsApproval() {                  // GOOD: business rule in domain
        order.Status = "needs_approval"
    }
    return u.orderRepo.Save(ctx, order)
}

Trigger Phrases

This skill activates when you say:

• "Audit architecture"
• "Check layer dependencies"
• "Review Clean Architecture"
• "Verify separation of concerns"
• "Check dependency rules"
• "Review usecase/repository pattern"
• "Check for layer violations"
• "Audit service structure"

How to Use

For Architecture Audit

1. Identify all layers in the codebase
2. Check dependency directions (must point inward)
3. Verify each layer's responsibilities
4. Flag violations with specific rule references

For Code Review

1. Identify which layer the code belongs to
2. Check against layer-specific rules
3. Verify dependencies are injected, not created
4. Ensure interfaces are defined by consumers

Output Format

## Architecture Violations: X

### [Rule Name] (File: path/to/file.go)
**Layer**: Delivery / Usecase / Repository / Domain
**Issue**: Brief description of violation
**Impact**: Tight coupling / Untestable / Wrong responsibility
**Fix**: Suggested correction
**Example**:
```go
// Corrected code

Related Skills

• golang-design-patterns - For refactoring large usecases
• golang-idiomatic-go - For interface design patterns
• golang-error-handling - For context propagation across layers

Philosophy

Based on Uncle Bob's Clean Architecture:

• Independence - Business rules don't depend on frameworks, UI, or databases
• Testability - Business logic can be tested without external dependencies
• Flexibility - Easy to swap implementations (e.g., change database)
• Maintainability - Clear boundaries make changes localized

Key Principle: The inner circles know nothing about the outer circles.

Notes

• Rules enforce separation of concerns in Go services
• Particularly focused on gRPC/usecase/repository pattern
• Emphasizes dependency injection for testability
• All examples follow Clean Architecture principles