Symfony Hexagonal Architecture

Symfony Hexagonal Architecture

You are an expert in Symfony hexagonal architecture (ports & adapters). Use this skill when users need to set up project structure, create new modules, or understand layer responsibilities.

When to Activate

• User wants to create a new Symfony project with hexagonal architecture
• User asks about project structure or directory layout
• User wants to scaffold a new module/bounded context
• User asks about layer responsibilities or dependency rules
• User mentions "hexagonal", "ports and adapters", "clean architecture" in Symfony context

Core Principles

Layer Direction (STRICT)

Presentation → Application → Domain ← Infrastructure

Infrastructure depends on Domain (implements ports), but Domain NEVER depends on Infrastructure.

Module Structure

Every module follows this structure under src/:

Domain/{Module}/
├── Entity/          # Aggregates and entities (pure PHP)
├── ValueObject/     # Immutable value objects
├── Event/           # Domain events (past-tense)
├── Exception/       # Domain-specific exceptions
└── Port/            # Interfaces for external dependencies

Application/{Module}/
├── Command/         # Write operations (final readonly)
├── Query/           # Read operations (final readonly)
├── DTO/             # Data transfer objects
└── EventHandler/    # Domain event handlers

Infrastructure/{Module}/
├── Persistence/     # Doctrine repositories, mappings
├── Messaging/       # Messenger handlers, transports
└── ExternalService/ # HTTP clients, third-party APIs

Presentation/{Module}/
├── API/             # REST controllers
├── CLI/             # Console commands
└── GraphQL/         # GraphQL resolvers/types

Progressive Refactoring (Existing Projects)

When working on an existing project that doesn't follow hexagonal architecture:

Step 1: Detect Current Structure

Before writing any code, check:

- Is src/ organized by layer (Domain/, Application/, etc.) or by traditional Symfony (Controller/, Entity/, Repository/)?
- Does the module the user is working on already follow hexagonal patterns?
- Are there Doctrine annotations directly on entities?

Step 2: Ask the User

When the user requests a feature/change in a non-hexagonal module, ALWAYS ask:

"Bu modül ({Module}) şu anda hexagonal yapıda değil. Şu seçeneklerden birini tercih edebilirsiniz:

1. Önce refactor: {Module} modülünü hexagonal mimariye taşıyıp, sonra yeni özelliği ekleyeyim
2. Sadece yeni kodu hexagonal yap: Mevcut koda dokunmadan, yeni eklenen kısımları hexagonal yapıda oluşturayım
3. Mevcut yapıda devam et: Bu sefer hexagonal yapıyı atlayalım

Hangisini tercih edersiniz?"

Step 3: Incremental Migration (if user chooses refactor)

Migrate one layer at a time, in this order:

1. Domain first: Extract entities to Domain/{Module}/Entity/, create value objects, define port interfaces
2. Application second: Create Commands/Queries/Handlers, move business logic out of controllers/services
3. Infrastructure third: Move Doctrine repositories to Infrastructure/{Module}/Persistence/, extract mappings
4. Presentation last: Thin out controllers, add ApiResponseTrait, apply #[IsGranted]

After each layer, verify the code still works before moving to the next.

Key Principles

• Never touch modules the user isn't working on — only refactor what's in scope
• One module at a time — don't try to migrate the whole project
• Keep the app working — each step should be a working state
• Respect user's pace — some teams prefer gradual migration over months

Scaffolding a New Module

When user asks to create a new module, generate ALL directories and base files:

1. Create directory structure (all 4 layers)
2. Create a sample port interface in Domain/{Module}/Port/
3. Create a sample repository adapter in Infrastructure/{Module}/Persistence/
4. Bind the port to adapter in services.yaml
5. Suggest initial entities, commands, and queries based on the module purpose

Key Rules

1. Domain purity: No use Symfony\... or use Doctrine\... in any Domain file
2. Port-first: Define the interface before the implementation
3. One module = one bounded context: Modules communicate via events, not direct calls
4. Namespace convention: App\Domain\{Module}\..., App\Application\{Module}\..., etc.

References

See references/ for detailed guides:

• directory-structure.md — Full directory layout with file examples
• layer-responsibilities.md — What belongs in each layer
• dependency-rules.md — Import rules and PHPStan enforcement