ipywidgets.Output() context suppresses exceptions

ipywidgets.Output() context manager supresses exceptions and prevents correct exit code

Description

For example take this code snippet and save it to a cell of a *.ipynb notebook.

import ipywidgets
o = ipywidgets.Output()
with o:
    raise Exception()
display(o)
print("execution continues")

Then execute the notebook with ipython:

$ ipython path/to/notebook.ipynb

The output will be

---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
/tmp/ipywidgets_bug/example.ipynb in <module>
      2 o = ipywidgets.Output()
      3 with o:
----> 4     raise Exception()
      5 display(o)
      6 print("execution continues")

Exception: 
Output()
execution continues

Expected behavior

The call to ipython should fail. If it is not aborted at the time when the exception is raised, at least it should exit with exit code other than 0.

Actual Behavior

The exception raised in the output context is suppressed. Execution continues and the ipython call exits with code 0.

Also the stderr output from the exception is not displayed unless display(o) is called explicitly. But this I reckon is expected behavior.

Context

• ipywidgets version
  8.0.0a4
• Operating System and version:
  archlinux kernel 5.12.7-arch1-1
• Browser and version:
  not used

Troubleshoot Output

$PATH:
	/tmp/ipywidgets_bug/.venv/bin
	/usr/local/bin
	/usr/bin
	/usr/local/sbin
	/opt/cuda/bin
	/opt/cuda/nsight_compute
	/opt/cuda/nsight_systems/bin
	/usr/lib/jvm/default/bin
	/usr/bin/site_perl
	/usr/bin/vendor_perl
	/usr/bin/core_perl
sys.path:
/tmp/ipywidgets_bug/.venv/bin
/usr/lib/python39.zip
/usr/lib/python3.9
/usr/lib/python3.9/lib-dynload
/tmp/ipywidgets_bug/.venv/lib/python3.9/site-packages
sys.executable:
/tmp/ipywidgets_bug/.venv/bin/python
sys.version:
3.9.5 (default, May 24 2021, 12:50:35)
[GCC 11.1.0]
platform.platform():
Linux-5.12.7-arch1-1-x86_64-with-glibc2.33
which -a jupyter:
/tmp/ipywidgets_bug/.venv/bin/jupyter
/usr/bin/jupyter
pip list:
Package            Version
------------------ -------
attrs              21.2.0
backcall           0.2.0
decorator          5.0.9
ipykernel          5.5.5
ipython            7.24.1
ipython-genutils   0.2.0
ipywidgets         8.0.0a4
jedi               0.18.0
jsonschema         3.2.0
jupyter-client     6.1.12
jupyter-core       4.7.1
jupyterlab-widgets 2.0.0a1
matplotlib-inline  0.1.2
nbformat           5.1.3
parso              0.8.2
pexpect            4.8.0
pickleshare        0.7.5
pip                21.1.1
prompt-toolkit     3.0.18
ptyprocess         0.7.0
Pygments           2.9.0
pyrsistent         0.17.3
python-dateutil    2.8.1
pyzmq              22.1.0
setuptools         56.0.0
six                1.16.0
tornado            6.1
traitlets          5.0.5
wcwidth            0.2.5
widgetsnbextension 4.0.0a2

Command Line Output

[TerminalIPythonApp] IPYTHONDIR set to: /home/XXXX/.ipython
[TerminalIPythonApp] Using existing profile dir: '/home/XXXX/.ipython/profile_default'
[TerminalIPythonApp] Searching path ['/tmp/ipywidgets_bug', '/home/XXXX/.ipython/profile_default', '/tmp/ipywidgets_bug/.venv/etc/ipython', '/usr/local/etc/ipython', '/etc/ipython'] for config files
[TerminalIPythonApp] Attempting to load config file: ipython_config.py
[TerminalIPythonApp] Looking for ipython_config in /etc/ipython
[TerminalIPythonApp] Looking for ipython_config in /usr/local/etc/ipython
[TerminalIPythonApp] Looking for ipython_config in /tmp/ipywidgets_bug/.venv/etc/ipython
[TerminalIPythonApp] Looking for ipython_config in /home/XXXX/.ipython/profile_default
[TerminalIPythonApp] Looking for ipython_config in /tmp/ipywidgets_bug
[TerminalIPythonApp] Loading IPython extensions…
[TerminalIPythonApp] Loading IPython extension: storemagic
[TerminalIPythonApp] Running file in user namespace: /tmp/ipywidgets_bug/example.ipynb
Exception                                 Traceback (most recent call last)
/tmp/ipywidgets_bug/example.ipynb in <module>
2 o = ipywidgets.Output()
3 with o:
----> 4     raise Exception()
5 display(o)
6 print(“execution continues”)
Exception:
Output()
execution continues
[TerminalIPythonApp] IPython not interactive…

[vidartf]

Thanks for the PR @wookayin . As a placeholder, you can also create a new widget by inheritance (no action in ipywidgets repo needed):

class NocatchOutput(ipywidgets.Output):
    def __exit__(self, *args, **kwargs):
        super().__exit__(*args, **kwargs)

[wookayin]

I submitted a PR #3417 that would fix this one. My proposal is to change the behavior on whether exceptions won’t be suppressed by default, but this would be up to core developers’ decision. Thank you for your considerations.