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# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
# For details: https://bitbucket.org/ned/coveragepy/src/default/NOTICE.txt
"""Monkey-patching to add multiprocessing support for coverage.py"""
import multiprocessing
import multiprocessing.process
import os
import sys
from coverage.misc import contract
# An attribute that will be set on the module to indicate that it has been
# monkey-patched.
PATCHED_MARKER = "_coverage$patched"
# The environment variable that specifies the rcfile for subprocesses.
COVERAGE_RCFILE_ENV = "_COVERAGE_RCFILE"
if sys.version_info >= (3, 4):
OriginalProcess = multiprocessing.process.BaseProcess
else:
OriginalProcess = multiprocessing.Process
original_bootstrap = OriginalProcess._bootstrap
class ProcessWithCoverage(OriginalProcess):
"""A replacement for multiprocess.Process that starts coverage."""
def _bootstrap(self):
"""Wrapper around _bootstrap to start coverage."""
from coverage import Coverage # avoid circular import
rcfile = os.environ[COVERAGE_RCFILE_ENV]
cov = Coverage(data_suffix=True, config_file=rcfile)
cov._warn_preimported_source = False
cov.start()
debug = cov._debug
try:
if debug.should("multiproc"):
debug.write("Calling multiprocessing bootstrap")
return original_bootstrap(self)
finally:
if debug.should("multiproc"):
debug.write("Finished multiprocessing bootstrap")
cov.stop()
cov.save()
if debug.should("multiproc"):
debug.write("Saved multiprocessing data")
class Stowaway(object):
"""An object to pickle, so when it is unpickled, it can apply the monkey-patch."""
def __init__(self, rcfile):
self.rcfile = rcfile
def __getstate__(self):
return {'rcfile': self.rcfile}
def __setstate__(self, state):
patch_multiprocessing(state['rcfile'])
@contract(rcfile=str)
def patch_multiprocessing(rcfile):
"""Monkey-patch the multiprocessing module.
This enables coverage measurement of processes started by multiprocessing.
This involves aggressive monkey-patching.
`rcfile` is the path to the rcfile being used.
"""
if hasattr(multiprocessing, PATCHED_MARKER):
return
if sys.version_info >= (3, 4):
OriginalProcess._bootstrap = ProcessWithCoverage._bootstrap
else:
multiprocessing.Process = ProcessWithCoverage
# Set the value in ProcessWithCoverage that will be pickled into the child
# process.
os.environ[COVERAGE_RCFILE_ENV] = rcfile
# When spawning processes rather than forking them, we have no state in the
# new process. We sneak in there with a Stowaway: we stuff one of our own
# objects into the data that gets pickled and sent to the sub-process. When
# the Stowaway is unpickled, it's __setstate__ method is called, which
# re-applies the monkey-patch.
# Windows only spawns, so this is needed to keep Windows working.
try:
from multiprocessing import spawn
original_get_preparation_data = spawn.get_preparation_data
except (ImportError, AttributeError):
pass
else:
def get_preparation_data_with_stowaway(name):
"""Get the original preparation data, and also insert our stowaway."""
d = original_get_preparation_data(name)
d['stowaway'] = Stowaway(rcfile)
return d
spawn.get_preparation_data = get_preparation_data_with_stowaway
setattr(multiprocessing, PATCHED_MARKER, True)
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