Add dependency injection system#25
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Handlers can now declare dependencies using Depends() in Annotated type
hints. The framework resolves them at call time before invoking the handler.
from typing import Annotated
from src import Depends
def get_db() -> MyDatabase:
return MyDatabase(url='...')
@kb.answer_ki(name='...', graph_pattern='...')
def handler(
binding_set: list[PersonBinding],
info: KnowledgeInteractionInfo,
db: Annotated[MyDatabase, Depends(get_db)],
) -> list[PersonBinding]:
return db.query(binding_set)
- src/depends.py: Depends(factory, cache=True) dataclass
- src/di.py: resolve_dependencies() — inspects Annotated hints, resolves
transitively, caches per-call by factory identity when cache=True
- KnowledgeBase.call(): resolves deps and passes as kwargs before handler call
- Depends exported from src public API
Behaviour:
- Sync-only factories (async deferred to a follow-up issue)
- Transitive resolution: factories can themselves declare Depends params
- cache=True (default): factory called once per KI call, result shared
- cache=False: factory called fresh every time it is needed
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Demonstrates Depends() with a realistic sensor-readings KB: - Basic injection: SensorRepository injected via Depends(get_sensor_repository) - Transitive deps: get_sensor_repository declares Depends(get_config) - Shared cache: get_config called once even though both the factory and the handler parameter depend on it Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Sophietje
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May 21, 2026
Sophietje
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I'm not sure about the filename di.py, it's not immediately clear that this will be a dependency injection resolver, perhaps rename to dependency_injection_resolver.py or dependency_resolver.py?
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Agreed and two separate files is unnecessary so renamed depends.py and di.py to dependency_injection.py |
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Adds FastAPI-like dependency injection system.
Define dependencies in handler arguments with a factory function that are loaded once per handler and work recursively (dependencies define their own dependencies), see example.