Comment # 6 on bug 1102261 from Tony Mechelynck

(In reply to Michael Andres from comment #4)
> Fixed for zypper-1.14.19

The current zypper version on openSUSE 15.1 is 1.14.27 which means it should
include this fix; its manpage is not very clear about this matter; it doesn't
mention --with-optional except at the end of the description of package type
"patch" at line 81.

I'll test this fix the next time an optional patch comes around for my system
(the only one so far for 15.1 is part of patch openSUSE-2019-1393 on the 15.1
Update-OSS repo, titled "test optional update for 15.1" and labeled "not
needed").