# Copyright 2015, Tresys Technology, LLC # # SPDX-License-Identifier: LGPL-2.1-only # from typing import MutableMapping from weakref import WeakKeyDictionary class DiffResultDescriptor: """Descriptor for managing diff results.""" # @properties could be used instead, but there are so # many result attributes, this will keep the code cleaner. def __init__(self, diff_function: str) -> None: self.diff_function = diff_function # use weak references so instances can be # garbage collected, rather than unnecessarily # kept around due to this descriptor. self.instances: MutableMapping = WeakKeyDictionary() def __get__(self, obj, objtype=None): if obj is None: return self if self.instances.setdefault(obj, None) is None: diff = getattr(obj, self.diff_function) diff() return self.instances[obj] def __set__(self, obj, value): self.instances[obj] = value def __delete__(self, obj): self.instances[obj] = None