Overlay annotations to indicate if a signal is supposed to already exist or not.

[erikbosch]

Today you can use overlays to both add new signals as well refactor existing signals. This gives a potential problem, if you do a spelling error or if a signal has been renamed or removed in standard VSS catalog your overlay may not do what you expect.

I am thinking if vss-tools possibly should support an attribute overlay: ['add'|'modify'] ( or similar like new: True|False) that could be used in overlays to describe if the overlay intend to add a new signal or change an existing signal. Then tooling could give a warning if the directive does not match reality.

Vehicle.Boddy.RefuelPosition:
  datatype: string
  type: attribute
  allowed: ['ALT1','ALT2']
  overlay: ['add'|'modify']
  description: Location of the fuel cap or charge port.

[SebastianSchildt]

maybe rather create or modify. (so that "add" can not be misunderstood as "adding" entries the allowed or instances (which is not the intention I guess)

And it should have a default, when not given. Not sure which is better, that depends how you use overlays :D