[stringtemplate-interest] need for null test

[Oliver Flege]

Hi,

we use an enhanced version of ST3 for xml rendering and while ST4 makes
most of our enhancements obsolete (in particular by supporting adaptors),
one crucial omission remains:

In order to render Boolean types declared as "xsd:boolean nillable=true" in an xsd,
we need to distinguish between false and null values, as the output has to
be either
<tag>false</tag> or <tag nil="true"/>, respectively.

I couldn't find any way to express this logic using ST4's if statement
given a Boolean attribute, as false and null both evaluate to false.

If that kind of logic can be expressed in ST4, I'd really appreciate any hint
on how its done; otherwise I think that a "test for null"-expression should be added
to the language, e.g., "if (?foo) ... "



Regards,
 Oliver