[stringtemplate-interest] how to fix longstanding bug

[Kunle Odutola]

Ter,

> Ok, so a bug exists with the rest(attribute) operator.  If you pass
> the result as a parameter it gets mess up if you ref that parameter
>  >1 time.  Here is the unit test that fails:
>
> /** BUG!  Fix this.  Iterator is not reset from first to second $x$
> *  Either reset the iterator or pass an attribute that knows to get
> *  the iterator each time.  Seems like first, tail do not
> *  have same problem as they yield objects.
> *
> *  Maybe make a RestIterator like I have CatIterator.
> */
> public void testRepeatedRestOpAsArg() throws Exception {

ST# has a RestCollection that handles this so, this unit tests passes in
ST#.

> It yields "Tom, " not "Tom, Tom".  I said, "oh, just reset iterator
> when you hit the end".  There *is* no reset method!  i cannot reset
> any incoming attributes as the following unit test shows:

C# IEnumerators can be reset. They aren't at the moment though.

> /** If an iterator is sent into ST, it must be cannot be reset after
> each
> *  use so repeated refs yield empty values.  This would
> *  work if we passed in a List not an iterator.  Avoid sending in
> iterators
> *  if you ref it twice.
> */
> public void testRepeatedIteratedAttrFromArg() throws Exception {

Fails on C# too (i.e. prints ietrator contents only one).

> Suggestions?  I'd really like at least the iterators I create to be
> "reusable" within same template.

Only sure way is to wrap *all* incoming iterators in a collection of some
sort. A bit like RestCollection does. Heavy-ish overhead unless, it is
possible to detect in advance if an iterator is indeed used repeatedly.

C# also has the option of simply Reset()-ing iterators but that breaks with
"positioned iterators" (i.e. iterators deliberately positioned at a specific
point in the underlying collection).


Kunle