Re: eldoc error in Emacs 27

[João Távora]

Yuan Fu <casouri@gmail.com> writes:

> 1.5. I looked around in that file and didn’t see elisp-eldoc-funcall
> defined anywhere (neither can I in the old eldoc.el that comes with
> Emacs 27).

Thanks for reporting this.  I introduced this bug.  The function you get
the error for is not defined in eldoc.el ? 1.5.0 but referenced there:

   (defun eldoc--eval-expression-setup ()
     ;; Setup `eldoc', similar to `emacs-lisp-mode'.  FIXME: Call
     ;; `emacs-lisp-mode' itself?
     (add-hook 'eldoc-documentation-functions
               #'elisp-eldoc-var-docstring nil t)
     (add-hook 'eldoc-documentation-functions
               #'elisp-eldoc-funcall nil t)
     (setq eldoc-documentation-strategy 'eldoc-documentation-default)
     (eldoc-mode +1))

Why is this Elisp-specific function in eldoc.el? Perhaps it shouldn't
be, but eldoc.el and elisp-mode.el are so unfortunately interwined so it
will have to remain there at least until we abandon Emacs 27 or make
elisp-mode.el a GNU ELPA :core package, too.

For now, the fix is to ensure that this function has an implementation
compatible with Emacs < 28, so that if you package-install a newer ElDoc
version you will not run into this problem.  The FIXME comment _could_
work in theory but I think it'll just bring more problems.  I'll post a
simpler, safer fix, soon.  In the meantime, can you make a bug report to
track this?

Thanks,
João