first draft of handling marker exceptions wrapped in exceptiongroup

[jakkdl]

I have barely used Hypothesis, and never worked with the codebase, so there are several gaps in code coverage and question marks on implementation decisions. If somebody more familiar wants to take a quick pass and opine it'd be very helpful :)

I can get code coverage by manually raising the specific ExceptionGroups that'll trigger the different branches, but it'd likely be better to do the actual things that causes those exceptions. So would likewise appreciate quick pointers on how to, if at all possible, cause e.g. multiple StopTest, multiple Frozen, a single Frozen, etc.

fixes #4106

[jobh]

Very nice, thanks! 👍

I think most of the build errors will go away with some of the minor commented changes, the remaining will hopefully be manageable :-)

[jobh]

Suggested change

	if sys.version_info < (3, 11):
	from exceptiongroup import ExceptionGroup
	from hypothesis.internal.compat import BaseExceptionGroup

[jobh]

Yep, the semantics here (generally) are a good question.

I'd opine:

• If all exceptions are Frozen, raise the first (as above).
• Else, if exactly one exception is non-Frozen, raise that one [*].
• Otherwise, reconstruct and raise a group with just the non-frozen ones (maybe .with_traceback(eg.__traceback__)).

[*] hm, I see, that would cause an undesired unwrapping if user code raises a single-exception ExceptionGroup. Maybe the second step should be "if exactly one ... and that exception is a StopException or HypothesisException.

[jobh]

I'd just catch BaseExceptionGroup (via hypothesis.internal.compat.BaseExceptionGroup) and check the subexceptions explicitly, to avoid the trio dependency.

[jakkdl]

ye that's probably the way to go. I'm incredibly biased on the matter as the person who wrote trio.testing.RaisesGroup and is trying to get it added to pytest 😇

[Zac-HD]

(and as a dual maintainer of Pytest and Trio, among other things, I'm pretty keen to support that when I have time 😅)

[jobh]

I can get code coverage by manually raising the specific ExceptionGroups that'll trigger the different branches, but it'd likely be better to do the actual things that causes those exceptions. So would likewise appreciate quick pointers on how to, if at all possible, cause e.g. multiple StopTest, multiple Frozen, a single Frozen, etc.

It should be possible to provoke most of these situations by playing around with multiple tasks failing in different ways. But I think it's fine to create the non-obvious situations explicitly, too.

[jobh]

It should be possible to provoke most of these situations by playing around with multiple tasks failing in different ways. But I think it's fine to create the non-obvious situations explicitly, too.

Sorry: "most" should probably be replaced by "some" 😁

[jobh]

Oh, and one other tip: hypothesis will transform/trim the tracebacks by default, which may be confusing sometimes when working on exceptions and not seeing what you'd expect. See get_trimmed_traceback().