When the support for reading snaps stage-packages from the primed-stage-packages manifest key was added, it was considered that if that the primed-stage-packages key was present, it should take precedence over all stage-packages of each part.
This is correct in general scenarios, but is failing under special scenarios such as the core snap, where the primed-stage-packages key is present in the snap manifest but is always empty.
When the support for reading snaps stage-packages from the primed- stage-packages manifest key was added, it was considered that if that the primed- stage-packages key was present, it should take precedence over all stage-packages of each part.
This is correct in general scenarios, but is failing under special scenarios such as the core snap, where the primed- stage-packages key is present in the snap manifest but is always empty.