Re: [O] [BUG] on export resulting in endless evaluation

[Charles Berry]

Rainer M Krug <Rainer <at> krugs.de> writes:

> 
> 
> Hi
> 
> when exporting the fillowing org file, I get an endless loop of
> evaluations.
> 
> This happens with only orgmode and languages enabled
> 
> ,----
> | GNU Emacs 24.4.1 (x86_64-apple-darwin14.0.0, Carbon Version 157
> | Org-mode version 8.3beta (release_8.3beta-798-g528b90  <at>  
> `----
> 
> --8<---------------cut here---------------start------------->8---
> #+PROPERTY: header-args :exports both
> #+PROPERTY: header-args+ :results output
> * The bug
> This file create an (possibly endless?) loop during export
> * here exports both
> #+begin_src R 
> cat(13+14)
> #+end_src
> 
> * and here only code
> :PROPERTIES:
> :header-args+: exports code
> :END:
> #+begin_src R 
> paste(13+14)
> #+end_src
> --8<---------------cut here---------------end--------------->8---
> 

Add this to the end of your example and run the src block:

--8<---------------cut here---------------start------------->8---

#+BEGIN_SRC emacs-lisp :results pp
(org-entry-get (point) "header-args" t)
#+END_SRC

#+RESULTS:
: ":exports both :results output exports code"

--8<---------------cut here---------------end--------------->8---


As you see the property API merely adds the `exports code' to the end of the
 "header-args"value.

Babel then ignores the 'exports' and you end up with `:results output code' 
which creates an executable src block. Since :exports both' is set, that src 
block is executed. And so on.

A bug? 

I guess Babel could do a better job of screening header-args and barf if 
invalid 
args are submitted. I believe that `org-babel-merge-params' is the place where 
a check could be introduced, but AFAICS there is none such.

Of course `:exports code' solves this, but I think you knew that. :-)

HTH,

Chuck