[FR, DISCUSSION] Re: [:results append] and [:wrap ...] don't play well together

[Ihor Radchenko <yantar92@gmail.com>]

Greg Minshall <minshall@umich.edu> writes:

> hi.  this fails with [emacs -Q], which in my case
> : Org mode version 9.4.4 (release_9.4.4 @ /usr/share/emacs/27.2/lisp/org/)
>
> and, also in whatever elpa'ish version i'm running
> : Org mode version 9.4.4 (release_9.4.4-277-g2e1c98 @ /home/minshall/.emacs.d/straight/build/org/)
>
> when i specify [:results append] and also [:wrap foo], the results are
> not obviously appended.  below it seems as if the second evaluation is
> appended, then the following are prepended after the first one?

I am replying late, but let's have an explanation for this issue as a
record at least.

The observed issue is not a bug, but rather a non-intuitive behaviour.

Let me explain how Org treats the described sequence of block
executions:

#+begin_src R :results append :wrap foo
Sys.time()
#+end_src

#1:

#+RESULTS:
#+begin_foo
2021-03-31 05:51:08
#+end_foo
<end of the results drawer; the result is first element after the block
with #+results keyword>

#2:

#+RESULTS:
#+begin_foo
2021-03-31 05:51:08
#+end_foo
<end of the results drawer; appending a new result>
#+begin_foo
2021-03-31 05:51:10
#+end_foo

#3:

#+RESULTS:
#+begin_foo
2021-03-31 05:51:08
#+end_foo
<end of the results drawer; appending a new result right here. The next
#drawer is _not_ considered a part of the result.>
#+begin_foo
2021-03-31 05:51:12
#+end_foo
#+begin_foo
2021-03-31 05:51:10
#+end_foo

And so on.

It is generally impossible to distinguish between a result consisting of
multiple paragraphs/drawers/other Org elements and the consequent
ordinary Org text. Consider:

#+begin_src elisp :results raw value
"paragraph 1

paragraph 2"
#+end_src

paragraph 3

Executing the above yields

#+begin_src elisp :results raw value
"paragraph 1

paragraph 2"
#+end_src

#+RESULTS:
paragraph 1

paragraph 2

paragraph 3

By looking at the #+RESULTS:, Org cannot possibly know if paragraph 2
belongs to the results or paragraph 3, or maybe just paragraph 1.

We may clarify this in the manual.

Another alternative could be treating
:results append drawer/code/pp/org/latex/html
differently and putting everything into a single drawer/src/export
environment like:

#+begin_src R :results append :wrap foo
Sys.time()
#+end_src

#3:

#+RESULTS:
#+begin_foo
2021-03-31 05:51:08
2021-03-31 05:51:10
2021-03-31 05:51:12
#+end_foo

However, changing the behaviour will be a breaking change, which we do
not want for the sake of back-compatibility.

Instead, we may introduce something like
:results append-contents drawer
that will behave like the above.

Is there a demand to have such a feature?

Best,
Ihor