tripack-container

High-level IoC container API of the Tripack framework: declarations, wiring, modules and bootstrap helpers used by application code.

tripack-container is the ergonomic surface most consumers import. It is built on top of the resolver in tripack-runtime and the protocols defined in tripack-contracts.

Install

uv add tripack-container
# or
pip install tripack-container

Optional extras:

# YAML configuration loader (PyYAML)
pip install 'tripack-container[yaml]'

# FastAPI integration (TripackAPI + Inject)
pip install 'tripack-container[fastapi]'

FastAPI integration

tripack_container.fastapi ships a drop-in FastAPI subclass that owns the container lifecycle and rewrites Annotated[T, Inject] parameters to FastAPI Depends at route registration time.

from pathlib import Path
from typing import Annotated, Protocol
from tripack_container import Inject
from tripack_container.fastapi import TripackAPI
from tripack_container.loaders import load_json


class Clock(Protocol):
    def now(self) -> float: ...


app = TripackAPI(
    container_factory=lambda: load_json(Path("container.json")),
)


@app.get("/now")
def now(clock: Annotated[Clock, Inject]) -> dict[str, float]:
    return {"now": clock.now()}

Three things happen behind the scenes:

1. The container is built (sync or async factory both work) at lifespan startup and aclosed at shutdown. A user-supplied lifespan= keyword still runs, layered inside the container's lifecycle.
2. Every HTTP request runs inside container.ascope() so SCOPED bindings cache per-request and their teardown fires at request end.
3. Each Annotated[T, Inject] parameter is rewritten to Annotated[T, Depends(...)] at route construction time; FastAPI's own dependency system then resolves T from app.state.container per request. app.dependency_overrides continues to work for tests.

The Inject marker

Sub-routers: TripackRouter

Sub-routers built with the default APIRouter analyse their routes at decoration time, before app.include_router runs, and crash on the bare Inject marker. Use TripackRouter instead - it defaults its route_class to the inject-aware variant:

from tripack_container.fastapi import TripackRouter

sub = TripackRouter(prefix="/v2")


@sub.get("/now")
def v2_now(clock: Annotated[Clock, Inject]) -> dict[str, float]:
    return {"now": clock.now()}


app.include_router(sub)

Architecture: three layers, one marker

Layer 3 (per-framework adapter)  tripack_container.fastapi   - TripackAPI subclass
Layer 2 (ASGI-agnostic)          tripack_container.asgi      - container_lifespan
                                                              + ContainerScopeMiddleware
Layer 1 (framework-agnostic)     tripack_container._inject   - Inject marker

• Layer 1 - Inject marker. A pure data class. No ASGI, no FastAPI, no Starlette. Every adapter reads it the same way through parse_inject(annotation).
• Layer 2 - ASGI primitives. container_lifespan is an @asynccontextmanager you can plug into any framework that accepts a lifespan (Starlette, FastAPI, Litestar, raw ASGI). ContainerScopeMiddleware is a pure ASGI middleware that opens container.ascope() per HTTP/WebSocket request. Test coverage includes a Starlette-only path that wires both primitives without importing FastAPI.
• Layer 3 - FastAPI adapter. TripackAPI composes the ASGI layer and adds the FastAPI-specific concern (rewriting Annotated[T, Inject] to Depends). A Starlette adapter would be a similar L3 module that re-uses L1 + L2 verbatim and adds its own route-level resolution mechanism.

The subclass choice for TripackAPI (rather than composite) is documented in the module docstring; the headline is that subclassing keeps isinstance(app, FastAPI) truthy so every FastAPI tool (TestClient, deployment runners, app.dependency_overrides) keeps working untouched while the constructor surface mirrors FastAPI(...).

Other ASGI frameworks (Starlette, Litestar, raw ASGI)

The L2 primitives - container_lifespan + ContainerScopeMiddleware - work without FastAPI. The ASGI integration guide ships the Starlette and raw-ASGI wiring templates plus the custom-accessor recipe for frameworks that keep app state outside app.state. Handlers there resolve from request.app.state.container manually - the Annotated[T, Inject] rewriting in L3 is the only piece that is FastAPI-specific.

Documentation

Project site: https://goabonga.github.io/tripack/.

License

MIT - see LICENSE.