Mini Shell

import functools
import logging
import pickle
from asyncio import iscoroutinefunction
from typing import Union, Callable

logger = logging.getLogger(__name__)


def _dump(path, obj):
    # separate function to mock in tests
    with open(path, "wb") as w:
        pickle.dump(obj, w)


def serialize_attr(*, path: str, attr: str):
    """
    Make decorator to serialize an object or object's attribute
    :param path: path to file to serialize into
    :param attr: attribute name to serialize
    """

    def decorator(f):
        @functools.wraps(f)
        def wrapper(self, *args, **kwargs):
            result = f(self, *args, **kwargs)
            obj = getattr(self, attr)
            logger.debug("Write %r to %r", obj, path)
            _dump(path, obj)
            return result

        @functools.wraps(f)
        async def async_wrapper(self, *args, **kwargs):
            result = await f(self, *args, **kwargs)
            obj = getattr(self, attr)
            logger.debug("Write %r to %r", obj, path)
            _dump(path, obj)
            return result

        if iscoroutinefunction(f):
            return async_wrapper
        return wrapper

    return decorator


def unserialize(*, path: str, fallback: Union[Callable, object] = None):
    """
    Restore an object from file
    :param path: path to read from
    :param fallback: return or call it if unserialization fails
    :return:
    """
    try:
        with open(path, "rb") as r:
            return pickle.load(r)
    except FileNotFoundError:
        logger.warning("Can't find %s to unserialize", path)
    except Exception as e:
        logger.error("Unserialize failed with %r. Returning an fallback", e)
    return fallback() if callable(fallback) else fallback