Skip flyspell checking of ~code~ and =verbatim= regions in Org mode

Question

First some disambiguation:

• This Endless Parentheses page demonstrates how to use ispell-skip-region-alist to skip =code= and =verbatim= blocks with ispell…

  (defun endless/org-ispell ()
    "Configure `ispell-skip-region-alist' for `org-mode'."
    (make-local-variable 'ispell-skip-region-alist)
    (add-to-list 'ispell-skip-region-alist '(org-property-drawer-re))
    (add-to-list 'ispell-skip-region-alist '("~" "~"))
    (add-to-list 'ispell-skip-region-alist '("=" "="))
    (add-to-list 'ispell-skip-region-alist '("^#\\+BEGIN_SRC" . "^#\\+END_SRC")))
  (add-hook 'org-mode-hook #'endless/org-ispell)
  

  …however, flyspell does not use ispell-skip-region-alist.

• This question on Emacs SX demonstrates how to skip flyspell checking for source blocks…

  ;; NO spell check for embedded snippets
  (defadvice org-mode-flyspell-verify (after org-mode-flyspell-verify-hack activate)
    (let* ((rlt ad-return-value)
           (begin-regexp "^[ \t]*#\\+begin_\\(src\\|html\\|latex\\|example\\|quote\\)")
           (end-regexp "^[ \t]*#\\+end_\\(src\\|html\\|latex\\|example\\|quote\\)")
           (case-fold-search t)
           b e)
      (when ad-return-value
        (save-excursion
          (setq b (re-search-backward begin-regexp nil t))
          (if b (setq e (re-search-forward end-regexp nil t))))
        (if (and b e (< (point) e)) (setq rlt nil)))
      (setq ad-return-value rlt)))
  

  …but not for inline code and verbatim region.

How can I achieve the ispell solution for flyspell, where Flyspell skips any regions surrounded by ~ or =? Generally I use these for things like variable names, which naturally tend to fail spellchecking.

Answer 1

It looks like this works out-of-the box with Emacs 26.3 and Orgmode 9.1.9. Source blocks and code snippets are not highlighted by flyspell with that Orgmode version. Maybe, you should just update.

To address the general problem:

You can ignore corrections proposed by flyspell by adding a function to flyspell-incorrect-hook. This hook already exists since Emacs 21.1. So it should be available even if you use an Emacs that old (for whatever reason).

I cite here the doc-string of flyspell-incorrect-hook:

List of functions to be called when incorrect words are encountered. Each function is given three arguments. The first two arguments are the beginning and the end of the incorrect region. The third is either the symbol ‘doublon’ or the list of possible corrections as returned by ‘ispell-parse-output’.

If any of the functions return non-nil, the word is not highlighted as incorrect.

It is easy to detect source blocks and code snippets with org-element-context.

Here comes the code that skips flyspell on source blocks and code snippets:

(defun org+-flyspell-skip-code (b e _ignored)
  "Returns non-nil if current word is code.
This function is intended for `flyspell-incorrect-hook'."
  (save-excursion
    (goto-char b)
    (memq (org-element-type (org-element-context))
      '(code src-block))))

(defun org+-config-flyspell ()
  "Configure flyspell for org-mode."
  (add-hook 'flyspell-incorrect-hook #'org+-flyspell-skip-code nil t))

(add-hook 'org-mode-hook #'org+-config-flyspell)

Tested on Emacs 26.3.

Answer 2

Check the current font face at point, if it's org-verbatim or org-code, then set the predicate's return value to nil. So Emacs knows the word at point is NOT a typo.

Here is the function to test font face at point,

(defun font-belongs-to (pos fonts)
  "Current font at POS belongs to FONTS."
  (let* ((fontfaces (get-text-property pos 'face)))
    (when (not (listp fontfaces))
      (setf fontfaces (list fontfaces)))
    (delq nil
          (mapcar (lambda (f)
                    (member f fonts))
                  fontfaces))))

To use this function, in https://emacs.stackexchange.com/a/9347/594 code, just below (when ad-return-value, insert one line,

(if (font-belongs-to (point) '(org-verbatim org-code)) (setq rlt nil))

BTW, you can check my org setup at https://github.com/redguardtoo/emacs.d/blob/98bef295ac515e5af43716d72a377494646653bf/lisp/init-org.el#L120 . The predicate there has more features and its code is more efficient.

Please note flyspell-incorrect-hook is NOT the right place for per mode setup. I explain the details in https://emacs.stackexchange.com/a/9347/594