[Rock-dev] [rock] #442: roby/syskit: Cleanup of Syskit::InstanceRequirements::Task

[rock]

#442: roby/syskit: Cleanup of Syskit::InstanceRequirements::Task
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 Reporter:  thro02  |       Owner:
     Type:  defect  |      Status:  new
 Priority:  major   |   Milestone:
Component:  base    |  Resolution:
 Keywords:  syskit  |
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Changes (by sylvain.joyeux):

 * priority:  normal => major


Comment:

 This '''is''' a limitation of Roby. The issue is that, from the p.o.v. of
 Roby's GC, the planned_by task is associated with task it is planning and
 therefore should not be cleared:

 This is what happens:
  - monster_interface::InterfaceModule has been added as a mission
    It is planned by Syskit::InstanceRequirements::Task::0x01
  - monster_interface::InterfaceModule is being added as a dependency of a
 SetPosture task (through the action), planned by
 Syskit::InstanceRequirements::Task::0x02
  - syskit merges both monster_interface::InterfaceModule tasks, leading to
 the resulting merged task being planned by both 0x01 and 0x02
  - SetPosture finishes
  - both planning tasks are associated with a mission, and therefore should
 not be removed.

 The proper solution is to add more merge tracking to Roby, so that Roby
 realizes that the planning task is associated with the dependency
 relation, NOT the task. Not trivial

 Instead of trying to tweak the GC (which can very easily have unintended
 consequences), I would suggest to do the proper thing manually, namely:

 {{{
 task = Sherpa::Tasks::SetPosture.new(arguments)
 monster = task.depends_on(
     monster_interface::InterfaceModule, :role => 'monster_interface')
 planner = monster.planning_task
 task.on :stop do |event|
   planner.remove_planned_task(planner.planned_task)
 end
 task
 }}}

 Since, within the action, the merge does not happen yet, you could also
 create a generic method that traverses the whole dependency tree, finds
 planning tasks and removes them if the toplevel action task finishes.

-- 
Ticket URL: <https://rock.opendfki.de/ticket/442#comment:1>
rock <https://rock.opendfki.de>
rock: the robot construction kit