105 lines
3.8 KiB
Python
105 lines
3.8 KiB
Python
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# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
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# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
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"""Monkey-patching to add multiprocessing support for coverage.py"""
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import multiprocessing
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import multiprocessing.process
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import os
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import os.path
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import sys
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import traceback
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from typing import Any, Dict
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# An attribute that will be set on the module to indicate that it has been
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# monkey-patched.
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PATCHED_MARKER = "_coverage$patched"
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OriginalProcess = multiprocessing.process.BaseProcess
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original_bootstrap = OriginalProcess._bootstrap # type: ignore[attr-defined]
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class ProcessWithCoverage(OriginalProcess): # pylint: disable=abstract-method
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"""A replacement for multiprocess.Process that starts coverage."""
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def _bootstrap(self, *args, **kwargs): # type: ignore[no-untyped-def]
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"""Wrapper around _bootstrap to start coverage."""
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try:
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from coverage import Coverage # avoid circular import
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cov = Coverage(data_suffix=True, auto_data=True)
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cov._warn_preimported_source = False
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cov.start()
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debug = cov._debug
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assert debug is not None
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if debug.should("multiproc"):
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debug.write("Calling multiprocessing bootstrap")
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except Exception:
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print("Exception during multiprocessing bootstrap init:")
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traceback.print_exc(file=sys.stdout)
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sys.stdout.flush()
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raise
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try:
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return original_bootstrap(self, *args, **kwargs)
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finally:
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if debug.should("multiproc"):
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debug.write("Finished multiprocessing bootstrap")
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cov.stop()
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cov.save()
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if debug.should("multiproc"):
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debug.write("Saved multiprocessing data")
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class Stowaway:
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"""An object to pickle, so when it is unpickled, it can apply the monkey-patch."""
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def __init__(self, rcfile: str) -> None:
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self.rcfile = rcfile
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def __getstate__(self) -> Dict[str, str]:
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return {"rcfile": self.rcfile}
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def __setstate__(self, state: Dict[str, str]) -> None:
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patch_multiprocessing(state["rcfile"])
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def patch_multiprocessing(rcfile: str) -> None:
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"""Monkey-patch the multiprocessing module.
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This enables coverage measurement of processes started by multiprocessing.
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This involves aggressive monkey-patching.
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`rcfile` is the path to the rcfile being used.
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"""
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if hasattr(multiprocessing, PATCHED_MARKER):
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return
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OriginalProcess._bootstrap = ProcessWithCoverage._bootstrap # type: ignore[attr-defined]
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# Set the value in ProcessWithCoverage that will be pickled into the child
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# process.
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os.environ["COVERAGE_RCFILE"] = os.path.abspath(rcfile)
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# When spawning processes rather than forking them, we have no state in the
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# new process. We sneak in there with a Stowaway: we stuff one of our own
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# objects into the data that gets pickled and sent to the sub-process. When
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# the Stowaway is unpickled, it's __setstate__ method is called, which
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# re-applies the monkey-patch.
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# Windows only spawns, so this is needed to keep Windows working.
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try:
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from multiprocessing import spawn
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original_get_preparation_data = spawn.get_preparation_data
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except (ImportError, AttributeError):
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pass
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else:
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def get_preparation_data_with_stowaway(name: str) -> Dict[str, Any]:
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"""Get the original preparation data, and also insert our stowaway."""
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d = original_get_preparation_data(name)
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d["stowaway"] = Stowaway(rcfile)
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return d
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spawn.get_preparation_data = get_preparation_data_with_stowaway
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setattr(multiprocessing, PATCHED_MARKER, True)
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