How to run indent command in arbitrary buffer while respecting user settings?

[Ihor Radchenko]

Hello,

In Org mode, we sometimes have a need to use third-party major mode to
do indentation:

#+begin_src emacs-lisp
(when t
'indent-me)
#+end_src

To do this, we currently create a major mode buffer containing the code
and run whatever is bound to <TAB> there.

This, however, is broken when user re-binds <TAB> to something else.
Or when something like evil-mode re-binds <TAB>
(https://github.com/emacs-evil/evil/issues/1806)

I am now considering running
(funcall-interactively #'indent-for-tab-command)

However, looking at 25 Indentation section of Elisp manual:

       The simplest way to perform indentation is the <TAB> key.  In most
    major modes, this runs the command ‘indent-for-tab-command’.  (In C and
    related modes, <TAB> runs the command ‘c-indent-line-or-region’, which
    behaves similarly, *note C Indent::).

I noticed that C and related modes have some alternative setting for
indentation. So, using `indent-for-tab-command' appear to be not as
reliable, after all.

Is there any reliable way to perform indentation in an arbitrary major
mode programmatically?

I notice that cc-mode.el has a comment that the current <TAB> re-binding
is at least debatable:

  (substitute-key-definition 'indent-for-tab-command
                             ;; XXX Is this the right thing to do
                             ;; here?
                             'c-indent-line-or-region
                             c-mode-base-map global-map)

So, should I simply ignore what cc-mode does and go ahead relying upon
`indent-for-tab-command' doing the right thing?

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>