bpo-36829: Add test.support.catch_unraisable_exception()#13490
bpo-36829: Add test.support.catch_unraisable_exception()#13490vstinner merged 3 commits intopython:masterfrom vstinner:catch_unraisable_exception
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* Copy test_exceptions.test_unraisable() to test_sys.UnraisableHookTest(). * test_exceptions.test_unraisable() uses catch_unraisable_exception(); simplify the test. test_sys now checks the exact output. * Use catch_unraisable_exception() in test_coroutines, test_exceptions, test_generators.
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I chose to leave test_io unchanged on purpose: I have a local branch which fix also https://bugs.python.org/issue36918 in Lib/_pyio.py and use this new catch_unraisable_exception() function. Once this PR will be merged, I will write a second PR based on it. |
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| self.assertEqual(repr(cm.unraisable.object), coro_repr) | ||
| self.assertEqual(cm.unraisable.exc_type, ZeroDivisionError) | ||
| self.assertIn("was never awaited", stream.getvalue()) |
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It's a little bit strange to have to catch half of the error message from stderr, and the other half from sys.unraisablehook. My PR #13488 will allow to inject the error message in the unraisable exception to catch both at the same time.
Lib/test/support/__init__.py
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| # check the expected unraisable exception | ||
| ... | ||
| finally: |
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this try/with/finally is somewhat tricky, how about:
try:
with support.throw_unraisable_exceptions():
...
except Exception as e:
... # the exception is now hereeg:
@contextlib.contextmanager
def throw_unraisable_exceptions():
unraisable = None
old_hook = sys.unraisablehook
def hook(exc):
nonlocal unraisable
unraisable = exc
sys.unraisablehook = hook
try:
yield
if unraisable is not None:
raise unraisable
finally:
unraisable = None
sys.unraisablehook = old_hookThere was a problem hiding this comment.
or recommend usage like this:
with support.catch_unraisable_exceptions() as cm:
...
cm.unraisable # only available here
assert cm.unraisable is None # now it's goneby updating __exit__:
def __exit__(self, *exc_info):
self.unraisable = None # clear unraisable here
sys.unraisablehook = self._old_hookThere was a problem hiding this comment.
Good idea :-) I implemented your __exit__ idea to avoid the need for try/finally.
throw_unraisable_exceptions() might be useful, but modified tests needs to access the 'obj' attribute of the unraisable hook. Later, they might also want to get access to the 'err_msg' attribute: #13488
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There's still a sharp edge here:
how about making cm.unraisable throw if accessed outside the context instead of being None, eg:
def __exit__(self, *exc_info):
del self.unraisable
sys.unraisablehook = self._old_hook
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and if you want to access additional unraisablehook info using throw_unraisable_exceptions:
class UnraisableException(Exception):
def __init__(self, unraisable):
self.unraisable = unraisable
super().__init__(self, unraisable)
@contextlib.contextmanager
def throw_unraisable_exceptions():
unraisable = None
old_hook = sys.unraisablehook
def hook(unraisable_):
nonlocal unraisable
unraisable = unraisable_
sys.unraisablehook = hook
try:
yield
if unraisable is not None:
raise UnraisableException(unraisable) from unraisable.exc_value
finally:
sys.unraisablehook = old_hookthen you can use it with:
try:
with throw_unraisable_exceptions():
...
except UnraisableException as e:
print(repr(e.__cause__))
err_msg = e.unraisable.err_msgThere was a problem hiding this comment.
I wrote PR #13554 to implement your "del self.unraisable" idea.
Avoid the need for try/finally: __exit__ clears unraisable to break the reference cycle.
4 participants
test_sys.UnraisableHookTest().
simplify the test. test_sys now checks the exact output.
test_exceptions, test_generators.
https://bugs.python.org/issue36829