(require 'notmuch-message)
;; From https://notmuchmail.org/pipermail/notmuch/2018/026423.html

;; attachment checks
;;
;; should be sent upstream, but needs unit tests in test/T310-emacs.sh
(defcustom notmuch-message-attach-regex
  "\\b\\(attache\?ment\\|attached\\|attach\\|pi[èe]ce\s+jointe?\\)\\b"
  "Pattern of text announcing there should be an attachment.

This is used by `notmuch-message-check-attach' to check email
bodies for words that might indicate the email should have an
attachement. If the pattern matches and there is no attachment (a
`<#part ...>' magic block), notmuch will show a confirmation
prompt before sending the email.

The default regular expression is deliberately liberal: we prefer
false positive than forgotten attachments. This should be
customized for non-english languages and notmuch welcomes
additions to the pattern for your native language, unless it
conflicts with common words in other languages."
  :type '(regexp)
  :group 'notmuch-send)

(defun notmuch-message-check-attach ()
  """Check for missing attachments.

This is normally added to `message-send-hook' and is configured
through `notmuch-message-attach-regex'."""
  (save-excursion ;; XXX: this fails somehow: point is at the end of the buffer on error
    (goto-char (point-min))
    (if (re-search-forward notmuch-message-attach-regex nil t)
        (progn
          (goto-char (point-min))
          (unless (re-search-forward "<#part [^>]*filename=[^>]*>" nil t)
            (or (y-or-n-p "Email seem to refer to attachment, but nothing attached, send anyways?")
                (error "No attachment found, aborting")))))))

(add-hook 'message-send-hook 'notmuch-message-check-attach)

(provide 'patch-notmuch)