Parameter substitution '+' fails

[chrishunter-agspace]

Sometimes a configuration setting should only be included if the corresponding argument is included. With normal parameter substitution this should be able to be accomplished with '+'. For example:

foo=100
echo ${foo+setting} ${foo:-}
$ setting 100

echo ${bar+setting} ${bar:-}
$

What actually happens is envplate complains:

Error while parsing 'configuration.conf': 'configuration.conf' requires undeclared environment variable 'foo', no default is given