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#!/usr/bin/env python
# cython: language_level=3
#
# delegators.py
"""
Decorators for functions that delegate parts of their functionality to other functions.
.. versionadded:: 0.10.0
"""
#
# Copyright © 2020 Dominic Davis-Foster <dominic@davis-foster.co.uk>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
# OR OTHER DEALINGS IN THE SOFTWARE.
#
# delegate_kwargs based on https://github.com/fastai/fastcore
# | 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.
#
# stdlib
import inspect
from typing import Callable, TypeVar, get_type_hints
__all__ = ["delegate_kwargs", "delegates"]
_C = TypeVar("_C", bound="Callable")
def delegate_kwargs(to: Callable, *except_: str) -> Callable[[_C], _C]:
r"""
Decorator to replace ``**kwargs`` in function signatures with the
parameter names from the delegated function.
:param to: The function \*\*kwargs is passed on to.
:param \*except\_: Parameter names not to delegate.
:raises ValueError: if a non-default argument follows a default argument.
""" # noqa: D400
# TODO: return annotation
def _f(f: _C) -> _C:
to_f, from_f = to, f
to_sig = inspect.signature(to_f)
from_sig = inspect.signature(from_f)
to_annotations = get_type_hints(to_f)
from_annotations = get_type_hints(from_f)
to_params = {k: v for k, v in to_sig.parameters.items() if k not in except_}
from_params = dict(from_sig.parameters)
if from_params.pop("kwargs", False):
if "kwargs" in from_annotations:
del from_annotations["kwargs"]
for param in from_params:
if param in to_params:
del to_params[param]
f.__signature__ = from_sig.replace( # type: ignore
parameters=[*from_params.values(), *to_params.values()]
)
f.__annotations__ = {**to_annotations, **from_annotations}
return f
return _f
def delegates(to: Callable) -> Callable[[_C], _C]:
r"""
Decorator to replace ``*args, **kwargs`` function signatures
with the signature of the delegated function.
:param to: The function the arguments are passed on to.
""" # noqa: D400
def copy_annotations(f):
if hasattr(to, "__annotations__"):
if hasattr(f, "__annotations__"):
return_annotation = f.__annotations__.get("return", inspect.Parameter.empty)
f.__annotations__.update(to.__annotations__)
if return_annotation is not inspect.Parameter.empty:
f.__annotations__["return"] = return_annotation
else:
f.__annotations__ = to.__annotations__
def _f(f: _C) -> _C:
to_sig = inspect.signature(to)
from_sig = inspect.signature(f)
from_params = dict(from_sig.parameters)
if tuple(from_params.keys()) == ("args", "kwargs"):
f.__signature__ = to_sig # type: ignore
copy_annotations(f)
elif tuple(from_params.keys()) == ("self", "args", "kwargs"):
f.__signature__ = from_sig.replace( # type: ignore
parameters=[from_params["self"], *to_sig.parameters.values()]
)
copy_annotations(f)
return f
return _f
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