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# Copyright 2015 gRPC 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.
"""Utilities for working with callables."""
from abc import ABC
import collections
import enum
import functools
import logging
_LOGGER = logging.getLogger(__name__)
class Outcome(ABC):
"""A sum type describing the outcome of some call.
Attributes:
kind: One of Kind.RETURNED or Kind.RAISED respectively indicating that the
call returned a value or raised an exception.
return_value: The value returned by the call. Must be present if kind is
Kind.RETURNED.
exception: The exception raised by the call. Must be present if kind is
Kind.RAISED.
"""
@enum.unique
class Kind(enum.Enum):
"""Identifies the general kind of the outcome of some call."""
RETURNED = object()
RAISED = object()
class _EasyOutcome(
collections.namedtuple(
"_EasyOutcome", ["kind", "return_value", "exception"]
),
Outcome,
):
"""A trivial implementation of Outcome."""
def _call_logging_exceptions(behavior, message, *args, **kwargs):
try:
return _EasyOutcome(
Outcome.Kind.RETURNED, behavior(*args, **kwargs), None
)
except Exception as e: # pylint: disable=broad-except
_LOGGER.exception(message)
return _EasyOutcome(Outcome.Kind.RAISED, None, e)
def with_exceptions_logged(behavior, message):
"""Wraps a callable in a try-except that logs any exceptions it raises.
Args:
behavior: Any callable.
message: A string to log if the behavior raises an exception.
Returns:
A callable that when executed invokes the given behavior. The returned
callable takes the same arguments as the given behavior but returns a
future.Outcome describing whether the given behavior returned a value or
raised an exception.
"""
@functools.wraps(behavior)
def wrapped_behavior(*args, **kwargs):
return _call_logging_exceptions(behavior, message, *args, **kwargs)
return wrapped_behavior
def call_logging_exceptions(behavior, message, *args, **kwargs):
"""Calls a behavior in a try-except that logs any exceptions it raises.
Args:
behavior: Any callable.
message: A string to log if the behavior raises an exception.
*args: Positional arguments to pass to the given behavior.
**kwargs: Keyword arguments to pass to the given behavior.
Returns:
An Outcome describing whether the given behavior returned a value or raised
an exception.
"""
return _call_logging_exceptions(behavior, message, *args, **kwargs)
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