Expanding FULLY a macro as argument

Question

I have a code line that looks like that

\includegraphics{\complicatedmacro}

The \complicatedmacro returns just the name of the picture file, e.g., mypicture, so that when I write

 \complicatedmacro

In my LaTeX code I get the text mypicture in the output .pdf

Consequently \includegraphics{\complicatedmacro} should just set the picture mypicture in the document. But I get an error

TeX capacity exceeded, sorry [input stack size=5000].

However when I write \includegraphics{mypicture}, everything works fine.

I have the feeling this issue has to do with the expansion process. What is the secret to let the \complicatedmacro be fully expanded before the call to \includegraphics?

I hope this is enough. I would like a general answer. But if you'd really need the "\complicatedmacro", I could write it.

Thanks! :)

The \complicatedmacro's definition

 \newcommand{\usedpicturename}[2]%
    {\ifthenelse{\boolean{shouldusetestpicture}}{#1}{#2}}

Use in the .tex file

Now somewhere in the code I set the boolean

   \setboolean{shouldusetestpicture}{false}
   \includegraphics{\usedpicturename{mypicturetest}{mypicturecool}} %Here pops up the error

Answer 1

ifthenelse does not work by expansion, it involves assignments so you can not "expand this fully". There are plenty of conditional macros that do work via expansion, such as

\newcommand{\usedpicturename}[2]%
    {\ifshouldusetestpicture #1\else #2\fi}