shwordsplit: final non-whitespace IFS character problem

[Martijn Dekker <martijn@xxxxxxxx>]

In field/word splitting, a final non-whitespace IFS delimiter character
is counted as an empty field. This is unlike every other current shell
(including current versions of pdksh, i.e. mksh and OpenBSD ksh).

Test script:

setopt shwordsplit
IFS=:
x=a:b:
set -- $x
echo $#

Expected output: 2
Actual output: 3

The POSIX standard appears pretty ambiguous on this:

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_05

https://osdn.jp/ticket/browse.php?group_id=3863&tid=35283#comment:3863:35283:1435293070
[click on "Show all old Histories" for complete discussion]

However, it turns out that the intention of the standard was clarified
back in 1995 (!) in:
http://www.open-std.org/JTC1/SC22/WG15/docs/rr/9945-2/9945-2-98.html

IOW, the intention of the POSIX standard is for IFS characters to be
field terminators rather than separators (in spite of the S in IFS).

Sorry if the timing of this is awkward (shortly before an upcoming release).

Thanks,

- M.