Hello Org Maintainers,
This issue has been reproduced on org versions 9.1.14 and Git master,
and comes with a patch.
* Issue
ob-haskell.el::org-babel-execute:haskell produces spurious error
messages when running haskell blocks without =:results output=
specified. If =:results= is not specified or is set to =value=, or
=silent=, evaluating haskell blocks with =C-c C-c= produces an error
message:
: org-babel-script-escape: ‘org-babel-script-escape’ expects a string".
Below is a minimal example that produces the unexpected behavior.
* ECM
The ECM is in two parts, below.
2. The Org sample that produces the error.
3. The minimal =~/.emacs=.
You may need to install the =ghc= package to get the =ghci=
executable.
** Org File
#+name: ecm-error-message
#+BEGIN_SRC org
1. Evaluate the addThree-delcare block to produce the error message.
If you receive an error about how =haskell-prompt-regexp= is
undefined, evaluate the block again, that is a transient error.
Create the =addThree= function that adds three to any number. Use
=:results silent= to suppress the RESULTS block because we don't
care about the results of a function declaration.
,#+name: addThree-declare
,#+begin_src haskell :results silent
:{
addThree :: (Num a) => a -> a
addThree x = x + 3
:}
,#+end_src
Observed behavior (without the patch below):
"org-babel-script-escape: ‘org-babel-script-escape’ expects a string"
With the patch:
(no output)
2. Apply the =addThree= function and get the result:
,#+name: addThree-apply
,#+begin_src haskell
addThree 10
,#+end_src
With and without the patch:
,#+RESULTS: addThree-apply
: 13
#+END_SRC
** .emacs
This is the minimal example .emacs file to produce this error:
#+BEGIN_SRC elisp
(require 'org)
(require 'ob-haskell)
(setq org-babel-load-languages '((haskell . t)))
#+END_SRC
* Patch
This unnecessary error message can be corrected with the following
patch that applies cleanly on both Debian Stable's Org version 9.1.14
and the current git master (commit
#93c50e3a7867a1a85fc78b337172585f7a10dcc6).
#+BEGIN_SRC diff
--- org-9.1.14/ob-haskell.el
+++ org-9.1.14/ob-haskell.el
@@ -92,7 +92,7 @@
(`output (mapconcat #'identity (reverse (cdr results)) "\n"))
(`value (car results)))))
(org-babel-result-cond (cdr (assq :result-params params))
- result (org-babel-script-escape result)))
+ result (if (stringp result) (org-babel-script-escape result))))
(org-babel-pick-name (cdr (assq :colname-names params))
(cdr (assq :colname-names params)))
(org-babel-pick-name (cdr (assq :rowname-names params))
#+END_SRC
This error may also prevent execution entirely in different
configurations, but I have not been able to reliably confirm that
behavior:
https://emacs.stackexchange.com/questions/35709/cannot-execute-org-babel-haskell-block
Thank you for your time,
Nick
