strict-abc

strict-abc provides StrictABCMeta and StrictABC, which validate concrete implementations of abstract methods at class definition time.

The goal is to fail fast when a subclass violates LSP-friendly signature rules.

Installation

pip install strict-abc-lsp

Usage

from abc import abstractmethod

from strict_abc import StrictABC


class BaseService(StrictABC):
    @abstractmethod
    def process(self, data: dict, cache: bool = True) -> str:
        ...


class ValidService(BaseService):
    def process(self, data: dict, cache: bool = True) -> str:
        return "ok"

This works.

But this raises TypeError at class definition time:

class InvalidService(BaseService):
    def process(self, data: dict, cache: bool) -> str:
        return "ok"

Because removing a default value strengthens the precondition.

Options

Configure validation with __strict_options__:

class Base(StrictABC):
    __strict_options__ = {
        "check_names": True,
        "check_defaults": True,
        "check_types": True,
        "check_return_type": True,
    }

    @abstractmethod
    def fetch(self, url: str) -> bytes:
        ...

Default options:

{
    "check_names": False,
    "check_defaults": True,
    "check_types": False,
    "check_return_type": False,
}

Development

Install dependencies:

make install

Run lint, type check, tests, build and dist check:

make all

Install pre-commit hooks:

make pre-commit-install

Run tests with coverage:

make cov

Publishing

For TestPyPI:

poetry config repositories.testpypi https://test.pypi.org/legacy/
poetry config pypi-token.testpypi <YOUR_TESTPYPI_TOKEN>
make publish-test

For PyPI:

poetry config pypi-token.pypi <YOUR_PYPI_TOKEN>
make publish

License

MIT