GNU bug report logs - #54639
26.1; (not (string-empty-p nil)) returns true

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ernesto Alfonso <erjoalgo <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.1; (not (string-empty-p nil)) returns true
Date: Wed, 30 Mar 2022 12:20:43 -0400

The expression (not (string-empty-p nil)) returns true. This is very
conuterintuitive: nil is as "empty" a value as there is! Some of the
more reasonable alternatives I can think of in order of preference are:

1. (string-empty-p nil) simply returns t
2. (string-empty-p nil) raises a type error
3. subr-x.el provides a separate string-null-or-empty-p function



In GNU Emacs 26.1 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.5)
 of 2019-09-22, modified by Debian built on x86-grnet-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
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Message #8 received at 54639 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Ernesto Alfonso <erjoalgo <at> gmail.com>
Cc: 54639 <at> debbugs.gnu.org
Subject: Re: bug#54639: 26.1; (not (string-empty-p nil)) returns true
Date: Thu, 31 Mar 2022 13:26:56 +0200

Ernesto Alfonso <erjoalgo <at> gmail.com> writes:

> The expression (not (string-empty-p nil)) returns true. This is very
> conuterintuitive: nil is as "empty" a value as there is!

But nil isn't a string, and the function is only (meant to be) valid for
strings.  It "works" for symbols by accident.

> Some of the more reasonable alternatives I can think of in order of
> preference are:
>
> 1. (string-empty-p nil) simply returns t
> 2. (string-empty-p nil) raises a type error

We can't change how an established function works -- that would break
people's code.

> 3. subr-x.el provides a separate string-null-or-empty-p function

That would be just (zerop (length OBJECT)), which doesn't quite seem
worth having a function when the function name is longer than the
expression it replaces.  (And it would be misleading to have the
function name start with string- since it works on other things, too.)

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

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