module_property.py

import importlib
import types

from typing import Any, Callable


class _staticproperty():
    def __init__(self, fget=None, fset=None, fdel=None, doc=None):
        self.fget = fget
        self.fset = fset
        self.fdel = fdel
        if doc is None and fget is not None:
            doc = fget.__doc__
        self.__doc__ = doc

    def __get__(self, instance, owner=None):
        return self.fget()

    def __set__(self, instance, value):
        return self.fset(value)

    def __delete__(self, instance):
        return self.fdel()

    def getter(self, fget):
        self.gset = fget
        return self

    def setter(self, fset):
        self.fset = fset
        return self

    def deleter(self, fdel):
        self.fdel = fdel
        return self


def module_property(func: Callable[..., Any]) -> _staticproperty:
    '''Similar to the ``property`` built-in, but works on modules.

    Cannot be acess directly, only available as a module attribute
    (eg. module.some_property).'''
    prop = _staticproperty(func)
    module = importlib.import_module(func.__module__)

    # we need to override the module type, so lets disallow this on custom module types
    if module.__class__ is not types.ModuleType:  # noqa: E721
        raise TypeError(
            'Can only set module properties on types.ModuleType modules '
            f'(expecting `{types.ModuleType}`, got `{module.__class__}`)'
        )

    class _CustomPropertyHolderModule(types.ModuleType):
        pass

    # replace module class and set a static property on the module
    module.__class__ = _CustomPropertyHolderModule
    setattr(module.__class__, func.__name__, prop)
    return prop