commands

Commands

Purpose: Handle write operations (create, update, delete) for domain aggregates with transaction management and event publishing

Purpose

• Handle write operations (create, update, delete) for domain aggregates.
• Coordinate transactions, domain event publishing, and command dispatching.
• Encapsulate business workflows that span multiple aggregates or external systems.

Structure

• Accept AbstractUnitOfWork, DomainEventPublisher, CommandProducer as core dependencies.
• Accept Protocol-based interfaces (e.g., ICanUpdateLineItems) for external system interactions.
• Use @retry_on_transaction_error() decorator on all methods that modify state.
• Maintain a logger instance for operation tracking.

Note on External Dependencies: The template includes imports for pubsub infrastructure (CommandProducer, DomainEventPublisher). You can customize the module path via the pubsub_module template variable, or it defaults to deps_pubsub. If your project uses different event/command infrastructure, provide the appropriate module path.

Behavior checklist

• Wrap aggregate operations in with self._uow: context manager.
• Load aggregates from repository or create new instances using domain factories.
• Invoke domain methods on aggregates to perform state changes.
• Save aggregates via self._uow.{aggregate_plural}.save(aggregate).
• Commit transaction with self._uow.commit().
• Publish domain events via _publish_events() helper after commit.
• Send commands via _send_commands() helper if aggregate emits commands.
• Log successful operations with appropriate detail level.
• Raise domain exceptions (e.g., AggregateNotFound) when aggregates are missing.

Testing guidance

• Write integration tests that verify transaction boundaries, event publishing, and command dispatching.
• Use fakes for Protocol interfaces to isolate external system interactions.
• Verify aggregate state changes and emitted events match expected outcomes.

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