How to disable abbrev-mode in all major modes?

[Rodrigo Morales <rodrigo-mailing-lists@morales.pe>]

Let me explain my use case: I want abbrev-mode to be disabled in all buffers because I want to expand abbreviations by explicitly calling the function =expand-abbrev=, but the default behavior is that abbreviations are expanded when pressing SPC, punctuations (e.g. PERIOD and COMMA) or C-i. After some investigation, I found out that abbrev-mode is enabled in message-mode (see next section for details on how I found that out).

I know that I can define a function that disables abbrev-mode and add it as a hook of those major modes where abbrev-mode is enabled by default, but I wonder if there is a cleaner way than doing this, because I don't want to be editing my configuration whenever I found out another major mode enables abbrev-mode by default.

#+BEGIN_SRC elisp
(defun my-abbrev-mode-disable ()
  (abbrev-mode -1))
(add-hook 'message-mode-hook 'my-abbrev-mode-disable)
#+END_SRC

*** Finding out abbrev-mode is enabled in message-mode

I started Emacs by using the command shown below:

#+BEGIN_SRC sh
emacs -Q
#+END_SRC

In the buffer =*scratch*=, the value of the variable =abbrev-mode= was nil, so I conclude that =abbrev-mode= was not enabled. The major mode of the buffer =*scratch*= was =lisp-interaction-mode=.

I called compose-mail (by default bound to =C-x m= in GNU Emacs 29.4). In the buffer =*unsent mail*=, the value of the variable =abbrev-mode= was t, so I conclude that =abbrev-mode= was enabled. The major mode of the buffer =*unsent mail*= was =message-mode=.