Re: [BUG] FAILED test-ob-python/session-multiline

[Ihor Radchenko <yantar92@posteo.net>]

Jack Kamm <jackkamm@gmail.com> writes:

>> If we can (eventually) remove some custom code from Org and move it to
>> Emacs, it will be the best for working towards RMS request
>> https://orgmode.org/list/E1kIPh1-0001Lu-Rg@fencepost.gnu.org
>
> I started down this path here:
>
> https://lists.gnu.org/archive/html/emacs-devel/2023-10/msg00004.html
>
> But I haven't followed up because I started to have some doubts. In
> particular, `python-shell-send-string-no-output' will terminate once it
> detects a prompt, so if some output looks like it ends in a prompt then
> it will terminate prematurely. Whereas in our current indicator-based
> approach, the user accidentally emitting
> `org-babel-python-eoe-indicator' is unlikely.

This problem is not new - it exist in comint.el itself.
I worked around it in ob-shell by re-defining prompt to be unique - see
`org-babel-shell-set-prompt-commands'. Of course, it is not a universal
solution.

> Another approach I have considered is to redirect sys.stdout from within
> Python. In particular, set it to a custom class inheriting from IOBase
> during the block's execution, that both prints and saves the output. I
> think this approach could ultimately be more robust, and without needing
> to print an ugly indicator token, but it could be complicated to do it
> right.

It may work, although it will affect certain workflows. I know that some
people use a mix of babel session blocks and manual comint buffer
interaction where they type commands manually. Hiding the output may not
be ideal in such scenario.

That said, the described scenario is somewhat buggy already.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>