For pluginlib to find all plugin-based packages in the ROS system, we should export the plugin description file inside package.xml. If we do not include this plugin, the ROS system won't find the plugins inside the package.

Here, we add the export tag to package.xml , as follows:

<export> 
  <pluginlib_calculator plugin="${prefix}/calculator_plugins.xml" /> 
</export> 

To work this export command properly, we should insert the following lines in package.xml:

 <build_depend>pluginlib_calculator</build_depend> 
 <run_depend>pluginlib_calculator</run_depend> 

The current package should directly depend on itself, both at the time of building and also at runtime.