domainkit

A Django-style framework for domain-driven FastAPI services. It provides:

• settings modules and installed domains
• manage.py commands and migrations
• DDD building blocks, with the layer rules between them enforced
• optional apps for reliable messaging, audit trails, and idempotent requests

pip install "domainkit[postgres]"     # extras: postgres, sqlite, metrics, tracing, testing

Documentation

• docs/reference.md: settings, middleware, errors, observability, testing, commands, and extension points
• docs/contrib.md: messaging, audit, and idempotency
• docs/versioning.md: compatibility, deprecations, and releases
• docs/adr/: the decisions behind the design
• CHANGELOG.md and SECURITY.md

Quick start

A project is a pyproject.toml, a manage.py, a config package, and a domains package for its bounded contexts. The project's name sets the environment variable prefix: billingAPI reads BILLING_API_*.

billing/
  pyproject.toml
  manage.py
  src/config/__init__.py
  src/config/settings/__init__.py
  src/config/settings/local.py
  src/config/settings/test.py
  src/config/urls.py
  src/config/asgi.py
  src/domains/__init__.py

# pyproject.toml
[project]
name = "billingAPI"
version = "0.1.0"
requires-python = ">=3.13"
dependencies = ["domainkit[sqlite]"]

[dependency-groups]
dev = ["domainkit[testing]"]                # pytest and httpx2, for the fixtures

[tool.pytest.ini_options]
pythonpath = ["src"]
addopts = "-p domainkit.testing"           # the database and client fixtures
domainkit_settings = "config.settings.test"

# manage.py
import sys
from pathlib import Path

if __name__ == "__main__":
    sys.path.insert(0, str(Path(__file__).resolve().parent / "src"))
    from domainkit.management import execute_from_command_line

    execute_from_command_line(sys.argv)

# src/config/settings/local.py
from pathlib import Path

from domainkit.conf.env import Env

env = Env()
BASE_DIR = Path(__file__).resolve().parents[3]

DEBUG = True
INSTALLED_DOMAINS = ["domainkit.contrib.messaging"]
ROOT_ROUTER = "config.urls.router"
ASGI_APPLICATION = "config.asgi:application"
DATABASES = {
    "default": {
        "URL": env.str("DATABASE_URL", f"sqlite+aiosqlite:///{BASE_DIR / 'db.sqlite3'}")
    },
}

# src/config/settings/test.py
from config.settings.local import *

DEBUG = False
ALLOWED_HOSTS = ["testserver"]
DATABASES = {"default": {"URL": "sqlite+aiosqlite:///:memory:"}}

# src/config/urls.py
from fastapi import APIRouter

from domainkit.http.health import router as health_router

router = APIRouter()
router.include_router(health_router)

# src/config/asgi.py
from domainkit.http import get_asgi_application

application = get_asgi_application()

Then:

pip install "domainkit[sqlite,testing]"                    # in a virtual environment
export BILLING_API_SETTINGS_MODULE=config.settings.local   # or put it in .env
python manage.py check
python manage.py startdomain invoices --aggregate Invoice   # prints how to install it
python manage.py makemigrations -m "create invoices" && python manage.py migrate
pytest                                                      # the generated tests
python manage.py runserver                                  # http://127.0.0.1:8000/docs

Developing domainkit

poetry install --all-extras            # Python 3.13
pre-commit install                     # after: pipx install pre-commit

poetry run ruff check . && poetry run ruff format --check . && poetry run mypy
poetry run pytest --cov                # random order; coverage gate in pyproject.toml
poetry run mutmut run "domainkit.http*" && poetry run mutmut results

CI (.github/workflows/ci.yml) runs the same checks on every push and pull request:

• lint and strict typing
• the tests on Python 3.13 and 3.14
• a wheel build, installed and imported in a clean environment
• pip-audit, and a gitleaks scan of the whole history

A full mutation testing run happens weekly. Releases are published to PyPI from a version tag; see docs/versioning.md.

License

MIT; see LICENSE.