Re: [PATCH] Set Python shell in Org edit buffer

[Jack Kamm]

Ihor Radchenko <yantar92@posteo.net> writes:

> See the attached tentative patch.

Thanks!

> ---
>  etc/ORG-NEWS     | 11 +++++++++++
>  lisp/ob-R.el     | 20 ++++++--------------
>  lisp/ob-julia.el | 16 +++++++++-------
>  3 files changed, 26 insertions(+), 21 deletions(-)

Not sure if you are doing this in a separate commit, but you also need
to make the change to org-src.el to remove

(org-babel-comint-buffer-livep session)

in `org-src-associate-babel-session'. Else,
`org-babel-R-associate-session' won't run if there's no live session,
and hence ESS won't create new session with the right name.

>  * Version 9.7 (not released yet)
>  ** Important announcements and breaking changes
> +*** ~org-edit-special~ no longer force-starts session in R and Julia source 
> blocks
> +
> +Previously, when R/Julia source block had =:session= header argument
> +set to a session name with "earmuffs" (like =*session-name*=),
> +~org-edit-special~ always started a session, if it does not exist.
> +
> +Now, ~org-edit-special~ arranges that a new session with correct name
> +is initiated only when user explicitly executes R/Julia-mode commands
> +that trigger session interactions.  The same session will remain
> +available in the context of Org babel.

I tested the patch (plus the additional change to org-src.el), with an
Org file with following 2 blocks:

#+begin_src R :session foo :results output
  print('foo')
#+end_src

#+begin_src R :session *bar* :results output
  print('bar')
#+end_src

On block "foo", I did C-', and then ess-eval-line. It creates a session
named "foo", as expected.

On block "*bar*", I did the same. It does not create session named
"*bar*", instead evaluating in session "foo". It seems ESS will always
assume you want to evaluate in existing session if one exists, rather
than start a new associated session, and it seems there is no way to
tell it to behave otherwise.

However, calling "M-x R" while editing block "*bar*" does create session
"*bar*" with correct name.

After sessions "foo" and "*bar*" have both been created, doing C-' and
then ess-eval-line will evaluate in the correct session.

It's annoying there's no way to tell ESS to start new session instead of
evaluating in existing one. Here are a few alternatives we could
consider to deal with this:

1. Change the worg/ORG-NEWS, to suggest users make sure the session
exists (either by evaluating a source block or call "M-x R" in edit
block) before running ess-eval-line.

2. Add ob-R and ob-julia customization options (as previously suggested)
to explicitly control the startup behavior (either to auto-start, or not).

3. Submit PR to ESS to add a variable we could let-bind, to force it to
start an associated session rather than evaluate in an existing
non-associated sessions.

Currently I lean towards a combination of #1 and #3, but am not sure,
and happy to go with whatever you think is best.