yaafcli 2026.2.6.43348

Minimal ASGI app scaffold

yaaf

YAAF stands for "Yet Another ASGI Framework".

A minimal Python ASGI app scaffold that discovers routes from the filesystem. It includes a tiny router and a CLI wrapper around uvicorn.

Design Goals and Opinions

• Filesystem-first routing. Routes are inferred from the directory structure under consumers/**/api rather than declared with decorators. This keeps routing discoverable by looking at the tree.
• Explicit endpoint files. Each route has _server.py and _service.py to separate request handling from domain logic.
• Dependency injection without wiring. Services are registered automatically and injected by name/type, so handlers and services focus on behavior, not setup.
• Static-first routing precedence. Static routes always win over dynamic segments, with warnings when a dynamic route would overlap a static route.
• Minimal core. The framework is intentionally small and opinionated, leaving room for you to add auth, middleware, validation, etc.

Quickstart

python -m venv .venv
source .venv/bin/activate
pip install -e .

# Run the built-in example routes
yaaf --reload

Example routes:

• GET /api/hello
• GET /api/<name> (dynamic segment)

Routing Model

Routes are inferred from the directory structure under any consumers/**/api directory.

• Every route directory must contain _server.py and _service.py.
• The route path is /api/... plus the sub-path after api/.
• Dynamic segments use [param] directory names and are exposed as params/path_params.

Example layout:

consumers/
  api/
    users/
      _server.py
      _service.py
    hello/
      _server.py
      _service.py
    [name]/
      _server.py
      _service.py

Handlers and Services

In _server.py, export functions named after HTTP methods (lowercase): get, post, etc. The function signature is resolved via dependency injection:

• request gives you the yaaf.Request object.
• params or path_params provides dynamic route parameters.
• Services are injected by type annotations.

Example _server.py:

from consumers.api import HelloService
from yaaf import Request
from yaaf.types import Params


async def get(request: Request, service: HelloService, params: Params):
    return {"message": service.message(), "path": request.path, "params": params}

In _service.py, expose a module-level service instance (or a callable like Service or get_service). Services are registered and can be injected into other services or handlers:

from consumers.api import UsersService


class Service:
    def __init__(self, users: UsersService) -> None:
        self._users = users

    def message(self) -> str:
        user = self._users.get_user("1")
        return f"Hello from yaaf, {user['name']}"

service = Service

Service-to-Service Injection

Services can depend on other services via type annotations. Example layout:

consumers/
  api/
    users/
      _service.py
      _server.py
    hello/
      _service.py
      _server.py

consumers/api/users/_service.py

class Service:
    def get_user(self, user_id: str) -> dict:
        return {"id": user_id, "name": "Austin"}

service = Service()

consumers/api/hello/_service.py

from consumers.api import UsersService


class Service:
    def __init__(self, users: UsersService) -> None:
        self._users = users

    def message(self) -> str:
        user = self._users.get_user("1")
        return f"Hello from yaaf, {user['name']}"

service = Service

consumers/api/hello/_server.py

from consumers.api import HelloService
from yaaf import Request


async def get(request: Request, service: HelloService):
    return {"message": service.message(), "path": request.path}

Running Another App

yaaf --app your_package.app:app

Versioning

This project uses calendar-based versions with a timestamp (UTC). To bump the version:

python scripts/bump_version.py

Service Type Generation

Every yaaf command regenerates consumers/api/__init__.py for type-checking. You can also run it explicitly:

yaaf gen-services

Dynamic route segments like [name] get Protocol stubs in the generated file since they are not valid import paths.