* System information
Emacs version: GNU Emacs 27.2
Org Mode version: Org mode version 9.4.4 (release_9.4.4 @
/usr/share/emacs/27.2/lisp/org/)
Operating system: Arch Linux
* The issue
In a freshly started Emacs (i.e. Emacs when it has been started through =emacs
-Q=), the value of the variable =org-babel-default-header-args= is
#+begin_src emacs-lisp
((:session . "none")
(:results . "replace")
(:exports . "code")
(:cache . "no")
(:noweb . "no")
(:hlines . "no")
(:tangle . "no")))
#+end_src
If we delete the cons cell whose car is =:tangle=. That is, if we evaluate the
following expression,
#+name: value-for-variable
#+begin_src emacs-lisp :results silent
(setq org-babel-default-header-args
'((:session . "none")
(:results . "replace")
(:exports . "code")
(:cache . "no")
(:noweb . "no")
(:hlines . "no")))
#+end_src
then the function =org-babel-tangle= will throw the following error =Wrong type
argument: stringp, nil= with the following backtrace
#+begin_example
Debugger entered--Lisp error: (wrong-type-argument stringp nil)
file-name-directory(nil)
org-babel-tangle-single-block(1)
org-babel-tangle-collect-blocks(nil nil)
org-babel-tangle(nil)
funcall-interactively(org-babel-tangle nil)
call-interactively(org-babel-tangle nil nil)
command-execute(org-babel-tangle)
#+end_example
* Reproducing the issue
You can reproduce this issue by
1. Start Emacs by executing =emacs -Q=.
2. Save the content of this message to a file whose extension is =org=.
3. Evaluate the expression shown above from the code block named
=value-for-variable=.
4. Execute =org-babel-tangle= be it interactively or through =eval-expression=.
* Additional information
This error can be avoided by explicitly having a =:tangle= header argument in
each code block.
* Personal thoughts
I had to spend more than 90 minutes looking for the expression in my
configuration that was causing this error. I think that either
+ showing a error message expressing that the =:tangle= header argument is not
set for some code blocks when =org-babel-tangle= is executed.
+ explicitly stating in the documentation that the =:tangle= header argument is
necessary for some functions to correctly work (e.g. =org-babel-tangle=)
could help other users to find this root cause so that they don't spend the
time I spent looking for the issue.
--
Greetings,
Rodrigo Morales.
IRC: rdrg109 (freenode)
