The_End/mods/items/undiggable_node_api/init.lua

undiggable_node_api = {}

--helper function
local function allow_remove_self(itemstack, user, pointed_thing)
	if pointed_thing.type == "node"
	then
		local node = minetest.get_node(pointed_thing.under)
		if node.name == itemstack:get_name()
		then
			minetest.remove_node(pointed_thing.under)
		end
	end
end



--API FUNCTION
--registers an undiggable node but it can be used as a tool to dig itself
undiggable_node_api.register_barrier = function(name, definition)
	definition.diggable = false
	definition.on_use = allow_remove_self

	definition.groups = definition.groups or {}
	definition.groups.indestructible = 1

	minetest.register_node(name, definition)
end