When either initializing with a non-constant value, or using the standard
[[ string widget = "null" ]] metadata. This can be used for inputs like
normals and texture coordinates, where you don't want to default to a
constant value.
In previous OSL versions the input value was automatically ignore when it
was left unchanged for such inputs. However that's no longer the case in
the latest version, breaking existing nodes. There is no good entirely
backwards compatible fix, but I believe the new behavior is better and will
keep most existing cases working.
Fix T102450: OSL node with normal input not working
dc1ed9c1aa