| # 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 | |