[stringtemplate-interest] bug? calling template with null argument

[John Snyders]

Hi all,
I am finding that I can't call a template with a null argument either
explicitly or by omission unless the call is made from the top level
template.

Here is an example of what I am trying to do:

page(name, value) ::= <<
 $input(name=name, value=value, size="22", ...)$
 $input(name=name, value=value, size="23", required="t", ...)$
>>

input(name, value, size, required) ::= <<
  <input type="text" name="$name$" size="$size$" value="$value$">
  $if(required)$
  <span class="required">*</span>
  $endif$
>>

This example works as intended. The output is
   <input type="text" name="input1" size="22" value="value 1">
   <input type="text" name="input1" size="23" value="value 1">
   <span class="required">*</span>

However, and here is the bug, when I nest the call to input in another
template (named or anonymous) I get an exception.
Example:
page(name, value) ::= <<
 $t2()$
 $input(name=name, value=value, size="22", ...)$
 $input(name=name, value=value, size="23", required="t", ...)$
>>

t2() ::= <<
 named template
 $input(name=name, value=value, size="21", ...)$
>>

Now I get this exception:
java.util.NoSuchElementException: no such attribute: required in template
context [page t2(...) input(...)]

I think this is a bug because the behavior of passing parameters to a
template should not depend on the nesting depth.

The problem seems to be in
StringTemplate.checkNullAttributeAgainstFormalArguments at the call to
lookupFormalArgument
    FormalArgument formalArg = self.lookupFormalArgument(attribute);
In the case where input is called from the top level the lookup finds the
argument required but when called from t2 it doesn't. It seems to be looking
in the wrong place. I need to do some more debugging. I'm a bit unclear on
the use of self vs. this. Can someone give an overview of what self is for.

Now if I remove the ... from the call to input in t2 it works. This example
doesn't need the ... but in my real work I do need to use the ...
The reason it works without the ... is because of this code in
StringTemplate.get which makes sense
 if ( o==null &&
   !self.passThroughAttributes &&
   self.getFormalArgument(attribute)!=null )
The call to checkNullAttributeAgainstFormalArguments is never made.

Any comments? Anyone seen this or can confirm that this is a bug or have a
fix?

Thanks,
-John
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