Why is type or ref required for layer in mapbox-gl-js

Question

mapbox-gl-js throws an error if a layer does not have a type. However, type is optional in the spec, and ref is not mentioned in the spec (was apparently taken out at some point). Can somebody clarify this? Should type be required then for the layer in the spec? Or something else?

Answer 1

I believe the documentation is out of date. type should not be optional now that ref has been deprecated. type should be required.

The style spec docs read:

type Optional enum. One of "fill", "line", "symbol", "circle", "heatmap", "fill-extrusion", "raster", "background".