Trio and PyCharm fighting over sys.excepthook

[ernestum]

The Apport error reporting mechanism of Ubuntu as well as PyCharm register custom sys.excepthooks. This causes the warning:

trio/_core/_multierror.py:472: RuntimeWarning: You seem to already have a custom sys.excepthook handler installed. I'll skip installing Trio's custom handler, but this means MultiErrors will not show full tracebacks.

and prevents uncaught multierrors from being printed properly.

I can reproduce this problem by simply running the following test.pyt:

import trio

from within PyCharm or on any Ubuntu/Mint machine that has the python3-apport packet installed.

A possible workaround is to run sys.excepthook = sys.__excepthook__ before importing trio but then the functionality of Apport/PyCharm will probably break.

Unfortunately there is no way to register multiple excepthooks in Python. However we might be able to "wrap" existing excepthooks instead of giving up in desparation?

[tjstum]

Hi!

Thanks for this detailed report. This was recently fixed (original issue #1065, fixed in #1528). This was included in the release 0.15.0 (and subsequent 0.15.1). Are you still seeing this issue even on the latest release?

[tjstum]

Oh, I guess you also described an issue with PyCharm's excepthook! Maybe we should leave this open but rename/change the summary to narrow the scope.

[njsmith]

Yeah, can you give more details on the PyCharm issue?

In PyCharm, what do you get if you do:

print(repr(sys.excepthook))
print(repr(sys.__excepthook__))

?

[mozesa]

<built-in function excepthook>
<built-in function excepthook>

Process finished with exit code 0

I hope it helped.

[njsmith]

Huh. And what do you get from 'print(sys.excepthook is sys.excepthook)'?

On Mon, May 25, 2020, 22:50 András Mózes [email protected] wrote:

Process finished with exit code 0

I hope it helped.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/python-trio/trio/issues/1553#issuecomment-633820405, or unsubscribe https://github.com/notifications/unsubscribe-auth/AAEU42BRFGTPG5BFTI3G7H3RTNKB3ANCNFSM4NJR55HA .

[mozesa]

I made a big misstake :(

import sys

import trio


print(repr(sys.excepthook))
print(repr(sys.__excepthook__))

<function trio_excepthook at 0x0000026AC55BE5E0>
<built-in function excepthook>

and now print(sys.excepthook is sys.__excepthook__) is False

(previously I didn't import trio)

[tjstum]

I was able to reproduce this using PyCharm. You have to use PyCharm's "debug" feature, not the normal "run" command:

Connected to pydev debugger (build 201.7223.92)
/.../site-packages/trio/_core/_multierror.py:472: RuntimeWarning: You seem to already have a custom sys.excepthook handler installed. I'll skip installing Trio's custom handler, but this means MultiErrors will not show full tracebacks.
  category=RuntimeWarning
<function _fallback_excepthook at 0x7fa29db23840>
<built-in function excepthook>

I think this is their excepthook.

[mozesa]

Yes it is true, in debug, always there is the warning.

[njsmith]

Well, adding special monkeypatches for each random library is obviously a terrible long-term approach. But in the short term, that looks like a pretty easy special monkeypatch to do. Something like: check for the PyCharm excepthook, and if it's found then monkeypatch the default_excepthook variable inside that module.

[dhirschfeld]

I have also noticed this warning in PyCharm but have so far ignored it 😬

[honglei]

same warning for WingPro8, just ignore it.

C:\Python310\lib\site-packages\trio\_core\_multierror.py:511: RuntimeWarning: You seem to already have a custom sys.excepthook handler installed. I'll skip installing Trio's custom handler, but this means MultiErrors will not show full tracebacks.
  warnings.warn(
<bound method CWhenPrintExceptionSupport.__ExceptHook of <debug.tserver.dbgutils.CWhenPrintExceptionSupport object at 0x000001D295CE65C0>>
<built-in function excepthook>
False

[Zac-HD]

Closing this in favor of https://github.com/agronholm/exceptiongroup/issues/23.