When DTLforeach is used with a condition, DTLiflastrow does not work

Question

In the following code, my dataset is {1,2,3,4}.

With no filter, DTLiffirstrow will return true at "1" and DTLiflastrow will return true at "4". This is what I expect from these functions.

When I filter the dataset to {2,3}, DTLiffisrtrow returns true at "2". Perfect.

But DTLiflastrow is always false. I would expect it to return true for the value "3".

\documentclass{article}

\usepackage{datatool}

\DTLnewdb{table}
\DTLnewrow{table}
\DTLnewdbentry{table}{C1}{1}
\DTLnewrow{table}
\DTLnewdbentry{table}{C1}{2}
\DTLnewrow{table}
\DTLnewdbentry{table}{C1}{3}
\DTLnewrow{table}
\DTLnewdbentry{table}{C1}{4}


\begin{document}


\DTLforeach*%
[\DTLisclosedbetween{\COne}{2}{3}]%
{table}%
{\COne=C1}%
{%
    \COne%
    \DTLiffirstrow{FIRST}{}%
    \DTLiflastrow{LAST}{}%
    \\%
}%

\end{document}

How could I detect the last row of a filtered set of data?

Answer 1

This is not a bug, it's a feature !

See the doc (datatool-code.pdf, around page 199):

\DTLiflastrow{〈true part 〉}{〈false part 〉}

Checks if the current row is the last row of the database. It doesn’t take the condition (the optional argument of \DTLforeach) into account, so its possible it may never do 〈true part〉, as the last row of the database may not meet the condition.

It is therefore not very useful and is confusing since it behaves differently to \DTLiffirstrow which does take the condition ...