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From: Denys Vlasenko <dvlasenk@redhat.com>
Newsgroups: gnu.bash.bug
Subject: Empty ""s in ARG in ${x:+ARG} expand to no words instead of the empty word if prepended/appended with space
Date: Fri, 20 Jul 2018 16:43:10 +0200
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Xref: csiph.com gnu.bash.bug:14372

$ f() { for i; do echo "|$i|"; done; }
$ x=x
$ e=

$  f ${x:+""}
||
^^^^^^^^^^^ correct

$ f ${x:+ ""}
^^^^^^^^^^^ prints nothing, bug?

$  ${x:+"" }
^^^^^^^^^^^ prints nothing, bug?

$ f ${x:+"$e"}
||
^^^^^^^^^^^ correct

$ f ${x:+ "$e"}
^^^^^^^^^^^ prints nothing, bug?

$ f ${x:+"$e""$e"""}
||
^^^^^^^^^^^ correct

$ f ${x:+"$e""$e"""}
^^^^^^^^^^^ prints nothing, bug?


Similarly with: f ${x:+"`echo`" } etc...