dependency-injection

Dependency Injection

Use this skill when handlers need shared services, repositories, config, or request-scoped resources.

Workflow

1. Define provider functions and wrap them with Provide.
2. Register dependencies at app/router/controller/handler scope.
3. Prefer narrow scope for overrides and testability.
4. Keep service lifecycle explicit (singleton vs request-scoped behavior).

Core Pattern

from litestar import Litestar, get
from litestar.di import Provide

def provide_settings() -> dict[str, str]: return {"env": "dev"}

@get("/env") async def read_env(settings: dict[str, str]) -> dict[str, str]: return settings

app = Litestar( route_handlers=[read_env], dependencies={"settings": Provide(provide_settings)}, )

## DI Checklist

- Use clear dependency keys (`settings`, `db_session`, `current_user`).
- Keep provider side effects controlled.
- Override dependencies in tests rather than monkeypatching internals.

## Litestar References

- https://docs.litestar.dev/latest/usage/dependency-injection.html