nested substitution args in launch files

edit

I cannot see an easy solution to your problem. I recommend supplying the absolute path of the file at command line. For instace:

roslaunch package file.launch robot:=`rospack find package_2`/relative/path/to/file

And using it directly as $(arg robot) in your launch file.

Depending on your exact application, there might be a better solution.

In case someone is stuck with older versions of roslaunch due to other dependencies, here is a workaround:

<arg name="robot"  default="mh5_mesh" />

<arg name="path"   value="(find $(arg robot)...)" />
<arg name="dollar" value="$" />

<include file="$(arg dollar)$(arg path)"  />

In my case I needed it to call the appropriate moveit_config file based on the robot and this hack works fine on ROS indigo