forked from zaclys/searxng
71 lines
2.6 KiB
Python
71 lines
2.6 KiB
Python
# SPDX-License-Identifier: AGPL-3.0-or-later
|
|
# lint: pylint
|
|
# pyright: basic
|
|
"""Module for backward compatibility.
|
|
|
|
"""
|
|
# pylint: disable=C,R
|
|
|
|
|
|
try:
|
|
from functools import cached_property # pylint: disable=unused-import
|
|
|
|
except ImportError:
|
|
|
|
# cache_property has been added in py3.8 [1]
|
|
#
|
|
# To support cache_property in py3.7 the implementation from 3.8 has been
|
|
# copied here. This code can be cleanup with EOL of py3.7.
|
|
#
|
|
# [1] https://docs.python.org/3/library/functools.html#functools.cached_property
|
|
|
|
from threading import RLock
|
|
|
|
_NOT_FOUND = object()
|
|
|
|
class cached_property:
|
|
def __init__(self, func):
|
|
self.func = func
|
|
self.attrname = None
|
|
self.__doc__ = func.__doc__
|
|
self.lock = RLock()
|
|
|
|
def __set_name__(self, owner, name):
|
|
if self.attrname is None:
|
|
self.attrname = name
|
|
elif name != self.attrname:
|
|
raise TypeError(
|
|
"Cannot assign the same cached_property to two different names "
|
|
f"({self.attrname!r} and {name!r})."
|
|
)
|
|
|
|
def __get__(self, instance, owner=None):
|
|
if instance is None:
|
|
return self
|
|
if self.attrname is None:
|
|
raise TypeError("Cannot use cached_property instance without calling __set_name__ on it.")
|
|
try:
|
|
cache = instance.__dict__
|
|
except AttributeError: # not all objects have __dict__ (e.g. class defines slots)
|
|
msg = (
|
|
f"No '__dict__' attribute on {type(instance).__name__!r} "
|
|
f"instance to cache {self.attrname!r} property."
|
|
)
|
|
raise TypeError(msg) from None
|
|
val = cache.get(self.attrname, _NOT_FOUND)
|
|
if val is _NOT_FOUND:
|
|
with self.lock:
|
|
# check if another thread filled cache while we awaited lock
|
|
val = cache.get(self.attrname, _NOT_FOUND)
|
|
if val is _NOT_FOUND:
|
|
val = self.func(instance)
|
|
try:
|
|
cache[self.attrname] = val
|
|
except TypeError:
|
|
msg = (
|
|
f"The '__dict__' attribute on {type(instance).__name__!r} instance "
|
|
f"does not support item assignment for caching {self.attrname!r} property."
|
|
)
|
|
raise TypeError(msg) from None
|
|
return val
|