Re: [Emacs-diffs] master 5811404: Replace eldoc-documentation-function with a hook

[Stefan Monnier]

>      […] advice should be reserved for the cases where you cannot modify
>      a function’s behavior in any other way.  If it is possible to do
>      the same thing via a hook, that is preferable (see Hooks).  […] In
>      particular, Emacs’s own source files should not put advice on
>      functions in Emacs.  (There are currently a few exceptions to this
>      convention, but we aim to correct them.)

A *-function variable is not an advice, but a hook.

It's a different kind of hook than those manipulated by add-hook (which
have names ending in -hook or -functions), but it's still a hook and
those have been used for many years in various parts of Emacs.

It just so happens that the operations that can manipulate those hooks
conveniently (add-function/remove-function) are provided in the same
file as the new advice-add, but that's only because it was convenient
and natural to implement advice-add on top of those new operations.


        Stefan