[BUG] ob-R: session evaluation returns empty ouputs with Org 9.6 [9.6 ( @ /home/fsantos/.emacs.d/elpa/org-9.6/)]

["Frédéric Santos" <frederic.santos@u-bordeaux.fr>]

Hi everyone,

With Org 9.6 released yesterday, I noticed a bug with ob-R: all R code
blocks with ":results output :session *R*" in the header will return no
output at all (although the code is correctly processed in the inferior
ESS buffer).

Steps to follow to reproduce the issue:

1. Create a minimal init.el file with this content (adapting paths if needed):

(add-to-list 'load-path "~/.emacs.d/elpa/org-9.6/")
(require 'org)
(add-to-list 'load-path "~/.emacs.d/elpa/ess-20221124.756/")
(require 'ess-site)
(org-babel-do-load-languages
 'org-babel-load-languages
 '((org . t)
   (R . t)))

2. Open emacs -Q -l init.el

3. Create an Org document with this content:

#+begin_src R :results output :session *R*
x <- 2:4
print(x)
#+end_src

4. Try to evaluate the R code block: you'll only get an empty output.

Note that external eval (i.e., without the :session arg) still works as
expected, and that other results types (e.g., :results value) still work
as well.

Bug confirmed by other ESS users on the mailing list:
https://stat.ethz.ch/pipermail/ess-help/2022-November/013162.html

Version info:
============
Emacs  : GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.34, cairo version 1.17.6) of 2022-09-12
Org    : Org mode version 9.6 ( @ /home/fsantos/.emacs.d/elpa/org-9.6/)
ESS    : ess-version: 18.10.3snapshot [elpa: 20221124.756]