# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt """Monkey-patching to add multiprocessing support for coverage.py""" import multiprocessing import multiprocessing.process import os import os.path import sys import traceback from typing import Any, Dict # An attribute that will be set on the module to indicate that it has been # monkey-patched. PATCHED_MARKER = "_coverage$patched" OriginalProcess = multiprocessing.process.BaseProcess original_bootstrap = OriginalProcess._bootstrap # type: ignore[attr-defined] class ProcessWithCoverage(OriginalProcess): # pylint: disable=abstract-method """A replacement for multiprocess.Process that starts coverage.""" def _bootstrap(self, *args, **kwargs): # type: ignore[no-untyped-def] """Wrapper around _bootstrap to start coverage.""" try: from coverage import Coverage # avoid circular import cov = Coverage(data_suffix=True, auto_data=True) cov._warn_preimported_source = False cov.start() debug = cov._debug assert debug is not None if debug.should("multiproc"): debug.write("Calling multiprocessing bootstrap") except Exception: print("Exception during multiprocessing bootstrap init:") traceback.print_exc(file=sys.stdout) sys.stdout.flush() raise try: return original_bootstrap(self, *args, **kwargs) 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: """An object to pickle, so when it is unpickled, it can apply the monkey-patch.""" def __init__(self, rcfile: str) -> None: self.rcfile = rcfile def __getstate__(self) -> Dict[str, str]: return {"rcfile": self.rcfile} def __setstate__(self, state: Dict[str, str]) -> None: patch_multiprocessing(state["rcfile"]) def patch_multiprocessing(rcfile: str) -> None: """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 OriginalProcess._bootstrap = ProcessWithCoverage._bootstrap # type: ignore[attr-defined] # Set the value in ProcessWithCoverage that will be pickled into the child # process. os.environ["COVERAGE_RCFILE"] = os.path.abspath(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: str) -> Dict[str, Any]: """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)