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# Copyright 2019 Google LLC
#
# 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
#
# https://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.
from typing import Type
import enum
import warnings
class EnumRule:
"""A marshal for converting between integer values and enum values."""
def __init__(self, enum_class: Type[enum.IntEnum]):
self._enum = enum_class
def to_python(self, value, *, absent: bool = None):
if isinstance(value, int) and not isinstance(value, self._enum):
try:
# Coerce the int on the wire to the enum value.
return self._enum(value)
except ValueError:
# Since it is possible to add values to enums, we do
# not want to flatly error on this.
#
# However, it is useful to make some noise about it so
# the user realizes that an unexpected value came along.
warnings.warn(
"Unrecognized {name} enum value: {value}".format(
name=self._enum.__name__,
value=value,
)
)
return value
def to_proto(self, value):
# Accept enum values and coerce to the pure integer.
# This is not strictly necessary (protocol buffers can take these
# objects as they subclass int) but nevertheless seems like the
# right thing to do.
if isinstance(value, self._enum):
return value.value
# If a string is provided that matches an enum value, coerce it
# to the enum value.
if isinstance(value, str):
return self._enum[value].value
# We got a pure integer; pass it on.
return value