How to toggle Org-mode source code block ":eval no" status

Question

I often limit or unlimit the evaluation of specific code blocks in org-mode babel using :eval header argument.

Here's an example:

#+BEGIN_SRC emacs-lisp :results value scalar :eval no
(+ 1 1)
#+END_SRC

#+RESULTS:
: 2

I toggle the code blocks between :eval no and :eval n (or delete :eval no completely) by hand.

#+PROPERTY: eval no is convenient, but is not suited for each code block.

Are there any better ways to toggle the :eval status handy, like below?

C-c C-t     (org-todo)
Rotate the TODO state of the current item among
(unmarked) -> TODO -> DONE

Answer 1

I've come up with a relatively nice solution, which relies on the org-in-block-p function, which I'd recommend taking a look. Add the following code to you init.el file:

(defun org-toggle-src-eval-no ()
  "Will toggle ':eval no' on the src block begin line"

  (defun in-src-block-p ()
    "Returns t when the point is inside a source code block"
    (string= "src" (org-in-block-p '("src"))))

  (defun beginning-src ()
    "Find the beginning of the src block"
    (let ((case-fold-search t)) (search-backward "#+BEGIN_SRC")))

  (defun toggle-eval-no ()
    "Handles the toggling of ' :eval no'"
     (save-excursion
      (end-of-line)
      (let ((case-fold-search t)) (search-backward "#+BEGIN_SRC")
       (if (search-forward " :eval no" (line-end-position) "f")
           (replace-match "")
         (insert " :eval no")
         ))))

  (if (in-src-block-p) (toggle-eval-no)))

(defun add-org-toggle-src-key ()
  (local-set-key (kbd "C-c t") (lambda () (interactive) (org-toggle-src-eval-no))))

(add-hook 'org-mode-hook 'add-org-toggle-src-key)

This defines the function org-toggle-src-eval-no and it should do exactly what you want; anytime you're inside a code block, it will toggle the presence of :eval no. I have bound it to C-c t, but feel free to map it to whatever you'd like. Happy org-ing.