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testing contextlib.contextmanager traceback
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#!/usr/bin/env python | |
# Copyright (c) 2016-2017 Intel Corporation | |
# | |
# 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. | |
from contextlib import contextmanager | |
from functools import wraps | |
import logging | |
import traceback | |
import sys | |
log_level = logging.DEBUG | |
logging.basicConfig(level=logging.DEBUG) | |
class MyGeneratorContextManager(object): | |
"""Helper for @contextmanager decorator.""" | |
def __init__(self, gen): | |
self.gen = gen | |
def __enter__(self): | |
try: | |
return self.gen.next() | |
except StopIteration: | |
raise RuntimeError("generator didn't yield") | |
def __exit__(self, exc_type, exc_val, exc_tb): | |
if exc_type is None: | |
try: | |
self.gen.next() | |
except StopIteration: | |
return | |
else: | |
raise RuntimeError("generator didn't stop") | |
else: | |
if exc_val is None: | |
# Need to force instantiation so we can reliably | |
# tell if we get the same exception back | |
exc_val = exc_type() | |
try: | |
# output = traceback.format_exception(exc_type, exc_val, exc_tb) | |
# output = traceback.format_exception(*sys.exc_info()) | |
# logging.error("\n".join(output)) | |
self.gen.throw(*sys.exc_info()) | |
# self.gen.throw(exc_type, exc_val, exc_tb) | |
raise RuntimeError("generator didn't stop after throw()") | |
except StopIteration, exc: | |
# Suppress the exception *unless* it's the same exception that | |
# was passed to throw(). This prevents a StopIteration | |
# raised inside the "with" statement from being suppressed | |
return exc is not exc_val | |
except: | |
# only re-raise if it's *not* the exception that was | |
# passed to throw(), because __exit__() must not raise | |
# an exception unless __exit__() itself failed. But throw() | |
# has to raise the exception to signal propagation, so this | |
# fixes the impedance mismatch between the throw() protocol | |
# and the __exit__() protocol. | |
# | |
if sys.exc_info()[1] is not exc_val: | |
raise | |
def my_contextmanager(func): | |
"""@contextmanager decorator. | |
Typical usage: | |
@contextmanager | |
def some_generator(<arguments>): | |
<setup> | |
try: | |
yield <value> | |
finally: | |
<cleanup> | |
This makes this: | |
with some_generator(<arguments>) as <variable>: | |
<body> | |
equivalent to this: | |
<setup> | |
try: | |
<variable> = <value> | |
<body> | |
finally: | |
<cleanup> | |
""" | |
@wraps(func) | |
def helper(*args, **kwds): | |
return MyGeneratorContextManager(func(*args, **kwds)) | |
return helper | |
# class suppress(object): | |
# | |
# def __init__(self, *args): | |
# super(suppress, self).__init__() | |
# self.exceptions = args | |
# | |
# def __enter__(self): | |
# pass | |
# | |
# def __exit__(self, exc_type, exc_val, exc_tb): | |
# if exc_type in self.exceptions: | |
# output = traceback.format_exception(exc_type, exc_val, exc_tb) | |
# logging.error("\n".join(output)) | |
@contextmanager | |
def suppress(*args): | |
try: | |
yield | |
except args as e: | |
if log_level <= logging.DEBUG: | |
logging.exception(e) | |
def reboot_switch_snmp(a, b, c, d, **kwargs): | |
logging.debug((a, b, c, d)) | |
logging.debug(kwargs) | |
def reboot_switch(**kwargs): | |
with suppress(TypeError): | |
return reboot_switch_snmp(**kwargs) | |
def main(): | |
reboot_switch(a=1) | |
if __name__ == "__main__": | |
main() | |
# bad traceback, using @contextmanager supress | |
# Note how the traceback stops at the yield statement, it does not show the actual calling location | |
#ERROR:root:reboot_switch_snmp() takes exactly 4 arguments (1 given) | |
#Traceback (most recent call last): | |
# File "test_supress.py", line 125, in suppress | |
# yield | |
# File "test_supress.py", line 138, in reboot_switch | |
# return reboot_switch_snmp(**kwargs) | |
#TypeError: reboot_switch_snmp() takes exactly 4 arguments (1 given) | |
# good traceback using suppress class | |
# Note how the traceback show the calling location in main(), reboot_switch() | |
#ERROR:root:Traceback (most recent call last): | |
# | |
# File "test_supress.py", line 138, in reboot_switch | |
# return reboot_switch_snmp(**kwargs) | |
# | |
#TypeError: reboot_switch_snmp() takes exactly 4 arguments (1 given) | |
# | |
#Traceback (most recent call last): | |
# File "test_supress.py", line 146, in <module> | |
# main() | |
# File "test_supress.py", line 142, in main | |
# reboot_switch(a=1) | |
# File "test_supress.py", line 138, in reboot_switch | |
# return reboot_switch_snmp(**kwargs) | |
#TypeError: reboot_switch_snmp() takes exactly 4 arguments (1 given) |
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