suppress expansion in macro call

Question

What I would like is to suppress the expansion of the group as a parameter to a macro so that it can be expanded later. For example we want to pass the paramater unmodified as a string to lua or to a file.

Let us suppose we have a macro \foo which accepts a parameter.

\def\foo#1{%
  \directlua{foo([[#1]]}%
  }

if we call it as: \foo{\bar{abc}} the \bar gets expanded before \foo gets to see it. Of course we can manually suppress the expansion with \foo{\noexpand\bar{abc}}, but can it be done automatically?

Answer 1

It doesn't really answer your question, but I think you are thinking about expansion wrong.

if we call it as: \foo{\bar{abc}} the \bar gets expanded before \foo gets to see it.

The argument to \foo is not expanded before \foo gets to see it. It is expanded inside \foo. Consider the following

\documentclass{article}
\def\foo#1{\def\bar{a}#1}
\begin{document}
\def\bar{x}
\foo{\bar}
\end{document}

If you want to expand \bar before \foo get to see it you need an \expandafter: \expandafter\foo\expandafter{\bar{abc}}

Answer 2

Without a full example to test this is untested but I would assume that you could go

\def\foo#1{%
  \directlua{foo([[\unexpanded{#1}]]}%
  }