[stringtemplate-interest] problem with null handling in parallel iteration

[Brian Lewis]

Would someone with a few free minutes *please* check the following
StringTemplate group and java code? I think it demonstrates a problem
with null handling in parallel iteration.

The output is
field1, label1, , 40
field2, label2, , 

I hope you will agree that the output *should* be
field1, label1, , null
field2, label2, , 40

test.stg:
group test;
/* "hack" gets me null. why isn't there an \N? */
hack ::= ["x":, default:]
test() ::= <<
$
["field1", "field2"],
["label1", "label2"],
[""      , ""      ],
[hack.x  , "40"    ]:
{name, label, required, size|
$name$, $label$, $required$, $size$
};null="null"$
>>

Test.java:
import java.io.*;
import java.util.*;
import org.antlr.stringtemplate.*;
import org.antlr.stringtemplate.language.*;

public final class Test
{
  public static void main(String[] arguments)
  {
    Test t = new Test();
    t.test();
  }

  public void test()
  {
    InputStream ins = getClass().getResourceAsStream("test.stg");
    InputStreamReader in = new InputStreamReader(ins);
    StringTemplateGroup g = new StringTemplateGroup(
      in,
      DefaultTemplateLexer.class
    );
    StringTemplate st = g.getInstanceOf("test");
    System.out.println(st.toString());
  }
}