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# Copyright 2024 The etils Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Contextvar util."""
from __future__ import annotations
import contextvars
import dataclasses
import functools
import typing
from typing import Any, Optional, TypeVar
from etils.edc import helpers
from typing_extensions import Annotated
_T = TypeVar('_T')
_Dataclass = Any
_DataclassT = TypeVar('_DataclassT')
_IS_CONTEXTVAR = object()
if typing.TYPE_CHECKING:
# TODO(b/254514368): Remove hack
class _ContextVarMeta(type):
def __getitem__(cls, value):
return value
class ContextVar(metaclass=_ContextVarMeta):
pass
else:
ContextVar = Annotated[_T, _IS_CONTEXTVAR] # pytype: disable=invalid-typevar
def make_contextvar_descriptor(
field: dataclasses.Field[Any], hint: helpers.Hint
) -> _ContextvarDescriptor:
"""Replace `ContextVar[]` annotated fields with contextvar descriptor."""
del hint
return _ContextvarDescriptor(field)
@dataclasses.dataclass
class _ContextvarDescriptor:
"""Descriptor to read-write individual contextvar."""
_field: dataclasses.Field[Any]
_objtype: type[Any] = dataclasses.field(init=False)
_attribute_name: str = dataclasses.field(init=False)
def __set_name__(self, objtype: type[_Dataclass], name: str) -> None:
"""Bind the descriptor to the class (PEP 487)."""
self._objtype = objtype
self._attribute_name = name
@functools.cached_property
def _var(self) -> contextvars.ContextVar[Any]:
"""Contextvar."""
default_kwargs = {}
if self._field.default is not dataclasses.MISSING:
default_kwargs['default'] = self._field.default
elif self._field.default_factory is not dataclasses.MISSING:
default_kwargs['default'] = self._field.default_factory()
else:
pass
return contextvars.ContextVar(self._attribute_name, **default_kwargs)
def __get__(
self,
obj: Optional[_Dataclass],
objtype: Optional[type[_Dataclass]] = None,
):
if obj is None:
return self
return self._var.get()
def __set__(self, obj: _Dataclass, value: Any) -> None:
self._var.set(value)
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