Initial checkin of gRPC to third_party/

third_party/grpc/src/python/grpcio/grpc/framework/foundation/callable_util.py

Index: third_party/grpc/src/python/grpcio/grpc/framework/foundation/callable_util.py
diff --git a/third_party/grpc/src/python/grpcio/grpc/framework/foundation/callable_util.py b/third_party/grpc/src/python/grpcio/grpc/framework/foundation/callable_util.py
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+# Copyright 2015, 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
+
+
+class Outcome(object):
+  """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.
+  """
+  __metaclass__ = abc.ABCMeta
+
+  @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)