Subject: bug#47388: 27.1; eldoc-documentation-function is ignore in updated eldoc

From: Stefan Monnier <[email-masked]>
Date: Sun, 28 Mar 2021 12:37:47 -0400

>   (when (function-equal #'ignore eldoc-documentation-function)
>         (setq-local eldoc-documentation-function #'eldoc-documentation-default|compose|whatever))))

BTW, using code like the one above is tolerable, usually for historical
reasons, but new APIs should aim not to need such things: comparing
functions is fundamentally always a hack.

        Stefan