Consider connect_sides for item transport

Previously connect_sides was only used to choose the correct visual
model, but not during item transport. This allowed items to exit tubes
in directions without a visual connection and enter objects from sides
that should not be connectable according to connect_sides.
For example an item could enter a chest from the front, if a tube passed
there.

This change saves the connect_sides in the meta table of the object
whenever the visual representation is updated. When nothing is cached
yet, it uses the old behavior. That way it does not break existing
builds.

autoplace_tubes.lua

@@ -53,27 +53,28 @@ local function tube_autoroute(pos)
 	}
 	-- xm = 1, xp = 2, ym = 3, yp = 4, zm = 5, zp = 6
 
-	local positions = {}
+	local adjlist = {} -- this will be used in item_transport
-	local nodes = {}
+
-	for i, adj in ipairs(adjustments) do
+	for i, adj in ipairs(adjustments) do
-		positions[i] = vector.add(pos, adj)
+		local position = vector.add(pos, adj)
-		nodes[i] = minetest.get_node(positions[i])
+		local node = minetest.get_node(position)
-	end
 
-	for i, node in ipairs(nodes) do
 		local idef = minetest.registered_nodes[node.name]
 		-- handle the tubes themselves
 		if is_tube(node.name) then
 			active[i] = 1
+			table.insert(adjlist, adj)
 		-- handle new style connectors
 		elseif idef and idef.tube and idef.tube.connect_sides then
-			local dir = adjustments[i]
+			if idef.tube.connect_sides[nodeside(node, vector.multiply(adj, -1))] then
-			if idef.tube.connect_sides[nodeside(node, vector.multiply(dir, -1))] then
 				active[i] = 1
+				table.insert(adjlist, adj)
 			end
 		end
 	end
 
+	minetest.get_meta(pos):set_string("adjlist", minetest.serialize(adjlist))
+
 	-- all sides checked, now figure which tube to use.
 
 	local nodedef = minetest.registered_nodes[nctr.name]

item_transport.lua

@@ -25,7 +25,7 @@ end
 -- both optional w/ sensible defaults and fallback to normal allow_* function
 -- XXX: possibly change insert_object to insert_item
 
-local adjlist={{x=0,y=0,z=1},{x=0,y=0,z=-1},{x=0,y=1,z=0},{x=0,y=-1,z=0},{x=1,y=0,z=0},{x=-1,y=0,z=0}}
+local default_adjlist={{x=0,y=0,z=1},{x=0,y=0,z=-1},{x=0,y=1,z=0},{x=0,y=-1,z=0},{x=1,y=0,z=0},{x=-1,y=0,z=0}}
 
 function pipeworks.notvel(tbl, vel)
 	local tbl2={}
@@ -80,6 +80,9 @@ local function go_next_compat(pos, cnode, cmeta, cycledir, vel, stack, owner)
 	if minetest.registered_nodes[cnode.name] and minetest.registered_nodes[cnode.name].tube and minetest.registered_nodes[cnode.name].tube.can_go then
 		can_go = minetest.registered_nodes[cnode.name].tube.can_go(pos, cnode, vel, stack)
 	else
+		local adjlist_string = minetest.get_meta(pos):get_string("adjlist")
+		local adjlist = minetest.deserialize(adjlist_string) or default_adjlist -- backward compat: if not found, use old behavior: all directions
+
 		can_go = pipeworks.notvel(adjlist, vel)
 	end
 	-- can_go() is expected to return an array-like table of candidate offsets.