[bug] $scalar[(pws[\0])1] or $scalar[(pws[á])1] doesn't work

[Stephane Chazelas <stephane@chazelas.org>]

From: https://unix.stackexchange.com/questions/724638/subscripted-variable-expansion-on-nul-delimited-words-in-zsh

Note that we're talking of the s[separator] *array subscript*
flag combined with w and p, not the s[separator] parameter
expansion flag here.

$ a=$'foo\0bar'
$ echo $a[(pws[\0])1]
f

Expected "foo".

It seems that's some missing metafication as confirmed by:

$ echo á | hd
00000000  c3 a1 0a                                          |...|
00000003

(0xa1 needing metafication as well)

$ a=fooábar
$ echo $a[(pws[á])1]
fooábar
$ a=fooébar
$ echo $a[(pws[é])1]
foo

$ n=$'\x83\x20' # a metafied NUL
$ a=$'foo\0bar'
$ eval "echo \$a[(pws[$n])1]"
foo

Also note the doc says about the "w" subscript flag:

> w
>    If the parameter subscripted is a scalar then this flag makes
>    subscripting work on words instead of characters.  The default word
>    separator is whitespace.[...]

I find that's not true. By default it seems to split on $IFS
characters (which by default does include space, tab and
newline but also NUL). Also I find empty elements are always
discarded even if $IFS-splitting with non-whitespace characters:


$ a=::foo:bar
$ echo $a[(ws[:])1]
foo
$ IFS=:
$ echo $a[(w)1]
foo

Also, it would be nice if one could do $a[(pws[$var])1] to align
with ${(ps[$var])var}

-- 
Stephane