Except hook incompatibility with exceptiongroup backport

[vxgmichel]

Since version 6.54.0, hypothesis uses exception notes (PEP 678) to show falsifying examples underneath the raised exception. With python < 3.11, this is done using a custom exception hook provided by exceptiongroup, a backport of PEP 654. The problem is that trio also uses a custom excepthook to manage multi-errors. In practice, this leads to the falsifying example not being displayed depending on the import order. Even worse, simply having pytest-trio installed causes the falsifying examples to disappear. Consider the following test:

from hypothesis import given
from hypothesis import strategies as st

@given(x=st.integers())
def test_notes(x):
    1/x

Without pytest-trio installed you would get:

    @given(x=st.integers())
    def test_notes(x):
>       1/x
E       ZeroDivisionError: division by zero
E       Falsifying example: test_notes(
E           x=0,
E       )

test_notes.py:7: ZeroDivisionError

And with pytest-trio installed:

    @given(x=st.integers())
    def test_notes(x):
>       1/x
E       ZeroDivisionError: division by zero

test_notes.py:7: ZeroDivisionError

[pquentin]

@agronholm Do you think #2213 would help here?

[agronholm]

Yup, since trio would no longer install its own hook. If you can manage to import exceptiongroup first, that would also work around this issue.

[pquentin]

Thanks I edited the description of #2213 so that it closes this issue when merged. A Trio release will quickly follow anyway, as it's a long awaited feature and Python 3.11 will be release next month.