Stop reindenting `if` after `else`

Question

Given the file test.c:

int main()
{
    if (a)
        foo();
    else
    if (b)      // line 6
        bar();
    else
        baz();
}

Whenever a comma or paren is typed while point is on line 6 (second if), Emacs reindents the line one indent level deeper, i.e.:

int main()
{
    if (a)
        foo();
    else
        if (b)
        bar();
    else
        baz();
}

Is there any way to disable this annoying behaviour just for this situation?

• I'm aware that I could use else if on one line instead of putting else and if on separate lines. However:
  • I don't like this style, as the if conditions are no longer aligned
  • I'm working on existing projects with an existing code style
  • The editor should not dictate the code style anyway.
• I'm aware that I could disable electric indentation entirely, however this disables useful behaviour such as correct indentation after typing { and }.

• The Emacs manual lists which characters trigger electric indentation:

  The electric characters are {, }, :, #, ;, ,, <, >, /, *, (, and ).

  However, there is no mention of any way to customizing them. I think leaving just { and } would be fine.

Answer 1

You could make c-mode follow your style like this:

(defun lineup-if-with-else (context)
  (pcase context
    (`(substatement . ,anchor)
     (save-excursion
       (back-to-indentation)
       (when (looking-at-p "if\\_>")
         (goto-char anchor)
         (when (looking-at-p "else\\_>")
           0))))))

(defun my-c-mode-hook ()
  "My `c-mode' hook."
  (c-set-offset 'substatement '(lineup-if-with-else +)))
(add-hook 'c-mode-hook 'my-c-mode-hook)

Answer 2

I guess one way is to simply unmap the undesired keys from the mode's keymap:

(eval-when-compile
  (require 'cc-mode))
(defun my-c-mode-hook ()
  "My `c-mode' hook."
  (define-key c-mode-map (kbd ",") nil)
  (define-key c-mode-map (kbd "(") nil)
  (define-key c-mode-map (kbd ")") nil))
(add-hook 'c-mode-hook 'my-c-mode-hook)