[Rock-dev] Getting rid of the "choice in starting state"

[Sylvain Joyeux]

I discussed this idea with a few people already, and had the same 
reaction from one guy that starts with Rock.

The distinction between "components that start in STOPPED state" and 
"components that start in PRE_OPERATIONAL state" makes no sense. I would 
personally get rid of it altogether, and make every component start in 
PRE_OPERATIONAL. Worstcase, the component will  do nothing when 
transitioned between PRE_OPERATIONAL and STOPPED.

To make the transition as painless as possible, I though of the following:

  * in tasks where needs_configuration is not added, make the default
    start state be PRE_OPERATIONAL, and warn the user that he should
    start using needs_configuration (so that he updates the
    task's constructors)
  * if a task where needs_configuration is not specified is started
    without being configured, call #configure automatically and warn
    that #configure should be called first.
  * after a while, make needs_configuration a noop and generate all
    tasks with the constructor that has no third parameter. Remove the
    backward compatibility measure in scripts.

The issue is that as soon as someone nicely adds needs_configure to a 
task, then the second backward compatibility measure is not going to 
work (i.e. it is going to break other people's script). I am therefore 
not sure what's the best way to do this transition.

In any case, it is not going to happen before rock's release.
-- 
Sylvain Joyeux (Dr.Ing.)
Space & Security Robotics

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