| # Copyright 2015-2016, Google Inc. |
| # All rights reserved. |
| # |
| # Redistribution and use in source and binary forms, with or without |
| # modification, are permitted provided that the following conditions are |
| # met: |
| # |
| # * Redistributions of source code must retain the above copyright |
| # notice, this list of conditions and the following disclaimer. |
| # * Redistributions in binary form must reproduce the above |
| # copyright notice, this list of conditions and the following disclaimer |
| # in the documentation and/or other materials provided with the |
| # distribution. |
| # * Neither the name of Google Inc. nor the names of its |
| # contributors may be used to endorse or promote products derived from |
| # this software without specific prior written permission. |
| # |
| # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| """Utilities for working with callables.""" |
| |
| import abc |
| import collections |
| import enum |
| import functools |
| import logging |
| |
| import six |
| |
| |
| class Outcome(six.with_metaclass(abc.ABCMeta)): |
| """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 |
| logging.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) |