bug#18088: 24.4.50; `region-extract-function': (1) NEWS, (2) return value

[Lars Ingebrigtsen]

Drew Adams <drew.adams@oracle.com> writes:

> Variable `region-extract-function' was apparently added in Emacs 24.4.
> It is used in several key places that affect killing or deleting text.
>
> 1. It should be called out in NEWS, saying what user-visible behavior
>    its presence changes.
>
> 2. The doc string points out that, depending on the value of its
>    argument, its return value is (a) significant and specified or (b)
>    insignificant and undefined.
>
>    This is the first time I have seen this for an Emacs function
>    distributed with GNU Emacs.  Certainly it is the first time I've
>    seen such odd behavior documented.
>
>    This does NOT seem like the kind of thing we should be doing - let
>    alone *encouraging* by defining a variable whose value will be
>    user-defined functions that have such twisted behavior.
>
>    Is this unusual design necessary?  Seems to be sloppy, error prone,
>    and an invitation to bad programming habits by users.

It seems like a quite complicated thing, but as it has been in a release
now, I think it's too late to do anything about that.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no