name : unraisableexception.py import sys import traceback import warnings from types import TracebackType from typing import Any from typing import Callable from typing import Generator from typing import Optional from typing import Type import pytest # Copied from cpython/Lib/test/support/__init__.py, with modifications. class catch_unraisable_exception: """Context manager catching unraisable exception using sys.unraisablehook. Storing the exception value (cm.unraisable.exc_value) creates a reference cycle. The reference cycle is broken explicitly when the context manager exits. Storing the object (cm.unraisable.object) can resurrect it if it is set to an object which is being finalized. Exiting the context manager clears the stored object. Usage: with catch_unraisable_exception() as cm: # code creating an "unraisable exception" ... # check the unraisable exception: use cm.unraisable ... # cm.unraisable attribute no longer exists at this point # (to break a reference cycle) """ def __init__(self) -> None: self.unraisable: Optional["sys.UnraisableHookArgs"] = None self._old_hook: Optional[Callable[["sys.UnraisableHookArgs"], Any]] = None def _hook(self, unraisable: "sys.UnraisableHookArgs") -> None: # Storing unraisable.object can resurrect an object which is being # finalized. Storing unraisable.exc_value creates a reference cycle. self.unraisable = unraisable def __enter__(self) -> "catch_unraisable_exception": self._old_hook = sys.unraisablehook sys.unraisablehook = self._hook return self def __exit__( self, exc_type: Optional[Type[BaseException]], exc_val: Optional[BaseException], exc_tb: Optional[TracebackType], ) -> None: assert self._old_hook is not None sys.unraisablehook = self._old_hook self._old_hook = None del self.unraisable def unraisable_exception_runtest_hook() -> Generator[None, None, None]: with catch_unraisable_exception() as cm: yield if cm.unraisable: if cm.unraisable.err_msg is not None: err_msg = cm.unraisable.err_msg else: err_msg = "Exception ignored in" msg = f"{err_msg}: {cm.unraisable.object!r}\n\n" msg += "".join( traceback.format_exception( cm.unraisable.exc_type, cm.unraisable.exc_value, cm.unraisable.exc_traceback, ) ) warnings.warn(pytest.PytestUnraisableExceptionWarning(msg)) @pytest.hookimpl(hookwrapper=True, tryfirst=True) def pytest_runtest_setup() -> Generator[None, None, None]: yield from unraisable_exception_runtest_hook() @pytest.hookimpl(hookwrapper=True, tryfirst=True) def pytest_runtest_call() -> Generator[None, None, None]: yield from unraisable_exception_runtest_hook() @pytest.hookimpl(hookwrapper=True, tryfirst=True) def pytest_runtest_teardown() -> Generator[None, None, None]: yield from unraisable_exception_runtest_hook()