Re: Bash-5.2-rc3 available

[Kerin Millar]

Hi Chet,

On Fri, 26 Aug 2022 14:28:00 -0400
Chet Ramey <chet.ramey@case.edu> wrote:

> 1. Changes to Bash
> 
> a. Added a compatibility mode feature that causes the parser to parse command
>    substitutions as if extglob were enabled. If it is enabled before 
> execution,
>    parse at execution will succeed. If not, the subsequent execution parse 
> will
>    fail.

I harbour some concerns as to both the utility and robustness of this.

$ declare -p BASH_VERSION
declare -- BASH_VERSION="5.2.0(1)-rc3"
$ shopt extglob
extglob         off
$ [[ '' = $(shopt extglob >&2) ]]
extglob         on
$ shopt extglob
extglob         on
$ grep -o extglob <<<"$BASHOPTS" | wc -c
0

For extglob to be arbitrarily enabled in either context is unexpected (and 
undesirable). For BASHOPTS not to be in agreement with the output of shopt is 
also unexpected. I presume that this is as a consequence of the above-mentioned 
change.

Paradoxically, this breaks one of the QA tests implemented by portage. I say 
paradoxically because I'm aware that Gentoo requested a concession pertaining 
to the relationship between the extglob option and the newly recursive parser. 
To put it in perspective, it transpired that only one ebuild (package) in its 
20620-strong repo was affected and that none of the portions of portage that 
are written in bash were affected (until now). My concern is that these 
ostensible concessions to backward-compatibility will end up causing more 
problems than will be solved.

--
Kerin Millar