mountaineer-di 0.1.3

Common dependency injection utilities for mountaineer & friends

mountaineer-di

Common dependency injection utilities for mountaineer & friends, with pydantic as the only dependency.

This package provides a small dependency resolver built around mountaineer_di.Depends(...). It works on its own, and when FastAPI is installed it can also interoperate with fastapi.Depends(...) inside the same dependency graph. You probably won't have to use this library explicitly but if it's helpful to you then you're certainly welcome to.

Getting Started

Install the package with uv:

uv add mountaineer-di

Native Usage

Use Depends(...) to declare dependencies, then resolve a callable with provide_dependencies(...):

from typing import Annotated

from mountaineer_di import Depends, provide_dependencies


def get_prefix() -> str:
    return "hello"


def get_message(prefix: str = Depends(get_prefix)) -> str:
    return f"{prefix} world"


async def handler(message: Annotated[str, Depends(get_message)]) -> str:
    return message


async with provide_dependencies(handler) as kwargs:
    result = await handler(**kwargs)
print(result)  # hello world

provide_dependencies(...) keeps generator and context-manager dependencies alive for the duration of the async context.

FastAPI Interop

If you're already using FastAPI elsewhere in your code, you can also use mountaineer-di to call into dependencies that use fastapi.Depends(...):

from fastapi import Depends as FastAPIDepends, Request

from mountaineer_di import Depends, get_function_dependencies


def get_user_agent(request: Request) -> str | None:
    return request.headers.get("user-agent")


def get_context(
    user_agent: str | None = FastAPIDepends(get_user_agent),
) -> str:
    return user_agent or "unknown"


async def task(context: str = Depends(get_context)) -> str:
    return context

For request-bound resolution, pass the request object and route template into get_function_dependencies(...) or provide_dependencies(...).

Development

Development commands are available through the repo Makefile, with lint, ci-lint, lint-ruff, lint-ty, and test targets following the same pattern as sibling Mountaineer repositories.