107 lines
3.6 KiB
Python
107 lines
3.6 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2013 Red Hat, Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import pdb
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import traceback
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def exception_handler(exc_info):
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"""Exception handler enabling post-mortem debugging.
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A class extending testtools.TestCase can add this handler in setUp():
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self.addOnException(post_mortem_debug.exception_handler)
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When an exception occurs, the user will be dropped into a pdb
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session in the execution environment of the failure.
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Frames associated with the testing framework are excluded so that
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the post-mortem session for an assertion failure will start at the
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assertion call (e.g. self.assertTrue) rather than the framework code
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that raises the failure exception (e.g. the assertTrue method).
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"""
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tb = exc_info[2]
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ignored_traceback = get_ignored_traceback(tb)
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if ignored_traceback:
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tb = FilteredTraceback(tb, ignored_traceback)
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traceback.print_exception(exc_info[0], exc_info[1], tb)
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pdb.post_mortem(tb)
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def get_ignored_traceback(tb):
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"""Retrieve the first traceback of an ignored trailing chain.
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Given an initial traceback, find the first traceback of a trailing
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chain of tracebacks that should be ignored. The criteria for
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whether a traceback should be ignored is whether its frame's
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globals include the __unittest marker variable. This criteria is
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culled from:
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unittest.TestResult._is_relevant_tb_level
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For example:
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tb.tb_next => tb0.tb_next => tb1.tb_next
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- If no tracebacks were to be ignored, None would be returned.
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- If only tb1 was to be ignored, tb1 would be returned.
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- If tb0 and tb1 were to be ignored, tb0 would be returned.
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- If either of only tb or only tb0 was to be ignored, None would
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be returned because neither tb or tb0 would be part of a
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trailing chain of ignored tracebacks.
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"""
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# Turn the traceback chain into a list
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tb_list = []
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while tb:
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tb_list.append(tb)
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tb = tb.tb_next
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# Find all members of an ignored trailing chain
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ignored_tracebacks = []
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for tb in reversed(tb_list):
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if '__unittest' in tb.tb_frame.f_globals:
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ignored_tracebacks.append(tb)
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else:
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break
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# Return the first member of the ignored trailing chain
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if ignored_tracebacks:
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return ignored_tracebacks[-1]
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class FilteredTraceback(object):
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"""Wraps a traceback to filter unwanted frames."""
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def __init__(self, tb, filtered_traceback):
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"""Constructor.
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:param tb: The start of the traceback chain to filter.
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:param filtered_traceback: The first traceback of a trailing
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chain that is to be filtered.
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"""
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self._tb = tb
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self.tb_lasti = self._tb.tb_lasti
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self.tb_lineno = self._tb.tb_lineno
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self.tb_frame = self._tb.tb_frame
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self._filtered_traceback = filtered_traceback
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@property
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def tb_next(self):
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tb_next = self._tb.tb_next
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if tb_next and tb_next != self._filtered_traceback:
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return FilteredTraceback(tb_next, self._filtered_traceback)
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