I'm trying to get a rule to generate header files with ruby code.  Optimally I'd like to be able to generate a header and/or a cpp, but for now a header will be fine.  Generation of just a cpp worked as explained in the documentation, however I was unable to get the the action rule for the header file to be called:

I was attempting something like:
import type ;
type.register RBHPP : rbhpp ; 
actions make-header

generators.register-standard rbconvert.make-header : RBHPP : HPP ;

Then I have a 
obj Foo.o : Foo.cpp : <dependency>Foo.rbhpp ;

If i touch Foo.rbhpp, it will rebuild Foo.cpp.  However it will never try and and execute the actions.

If is replace s/hpp/cpp.  It works as expected (putting Foo.rbcpp in the sources location).

Do I need to use a more advanced generator class to make the actions to execute?