Subject: Re: bug#23750: 25.0.95; bug in url-retrieve or json.el

From: Dmitry Gutov <[email-masked]>
Date: Mon, 20 Jun 2016 20:16:37 +0300

On 06/20/2016 05:38 PM, Eli Zaretskii wrote:

> Or just use concat,
> and test the result with multibyte-string-p before sending.

Actually, here's a reason why we might prefer not to replace 
string-as/to-unibyte with multibyte-string-p: string-to-unibyte works 
fine if the string's contents only contain ASCII/8-bit characters, even 
if the string itself is multibyte. But multibyte-string-p returns nil 
for such strings anyway.

So doing like you suggest might make some (arguably not well-written) 
programs fail, which otherwise could function fine, provided they only 
operate on ASCII strings. And having a multibyte string with ASCII-only 
contents is fairly common when the string is produced with 
buffer-substring from a source code buffer.

While it might be good to discourage this kind of programming practice 
(that doesn't handle non-ASCII text properly), it seems like this would 
be better for master rather that the impending release.

WDYT?