asphalt-framework/asphalt-serialization

from __future__ import annotations

from typing import Any

from asphalt.core import qualified_name


def default_marshaller(obj: Any) -> Any:
    """
    Retrieve the state of the given object.

    Calls the ``__getstate__()`` method of the object if available, otherwise returns
    the ``__dict__`` of the object.

    :param obj: the object to marshal
    :return: the marshalled object state

    """
    if hasattr(obj, "__getstate__"):
        return obj.__getstate__()

    try:
        return obj.__dict__
    except AttributeError:
        raise TypeError(
            f"{qualified_name(obj.__class__)!r} has no __dict__ attribute and does not "
            f"implement __getstate__()"
        ) from None


def default_unmarshaller(instance: Any, state: Any) -> None:
    """
    Restore the state of an object.

    If the ``__setstate__()`` method exists on the instance, it is called with the state
    object as the argument. Otherwise, the instance's ``__dict__`` is replaced with
    ``state``.

    :param instance: an uninitialized instance
    :param state: the state object, as returned by :func:`default_marshaller`

    """
    if hasattr(instance, "__setstate__"):
        instance.__setstate__(state)
    else:
        try:
            instance.__dict__.update(state)
        except AttributeError:
            raise TypeError(
                f"{qualified_name(instance.__class__)!r} has no __dict__ attribute and "
                f"does not implement __setstate__()"
            ) from None