Undefined-function error about function called by my function

Question

I have recently moved to emacs as my mail client. I am using message-mode to write and send email through notmuch. Specifically, the major mode is called Message[Notmuch].

I would like to remap C-c C-c (mail-send-and-exit) and C-c C-s (mail-send) to safe analogues that require a confirmation in the minibuffer before the email is sent. So far I have:

(defun safe-mail-send-and-exit ()
  (interactive)
  (if (string-equal (read-from-minibuffer "Are you sure? ") "yes")
      (mail-send-and-exit)
    (message "Not sent!")))

When I call this function within message-mode, I get an error:

Symbol’s function definition is void: mail-send-and-exit

How can I pass the context of the email and the mode to my function?

Answer 1

Put (require 'THE-LIBRARY) inside your definition of safe-mail-send-and-exit, at the beginning (just after (interactive), where THE-LIBRARY is the library that defines function mail-send-and-exit.

(defun safe-mail-send-and-exit ()
  (interactive)
  (require 'THE-LIBRARY) ; Replace THE-LIBRARY with the right library name.
  (if (string-equal (read-from-minibuffer "Are you sure? ") "yes")
      (mail-send-and-exit)
    (message "Not sent!")))

Or else ensure that you load that library before defining (or at least before invoking) that function. E.g.:

(with-eval-after-load THE-LIBRARY
  (defun safe-mail-send-and-exit ()
   ;; ...
   ))

---

Not part of your question, but consider replacing this:

(string-equal (read-from-minibuffer "Are you sure? ") "yes")

with just this:

(yes-or-no-p "Are you sure? ")