add building_lib.get_building_def_at

common.lua

@@ -1,9 +1,11 @@
 
+-- returns the origin of the placed building
 function building_lib.get_origin(mapblock_pos)
 	local _, origin = mapblock_lib.resolve_data_link(building_lib.store, mapblock_pos)
 	return origin
 end
 
+-- returns the building_info on the position
 function building_lib.get_placed_building_info(mapblock_pos)
 	local mapblock_data, origin = mapblock_lib.resolve_data_link(building_lib.store, mapblock_pos)
 	if mapblock_data and mapblock_data.building then
@@ -11,6 +13,21 @@ function building_lib.get_placed_building_info(mapblock_pos)
 	end
 end
 
+-- returns the building_def on the position
+function building_lib.get_building_def_at(mapblock_pos)
+	local info, origin = building_lib.get_placed_building_info(mapblock_pos)
+	if not info then
+		return false, "no building found"
+	end
+
+	local building_def = building_lib.get_building(info.name)
+	if not building_def then
+		return false, "building_def not found for '" .. info.name .. "'"
+	end
+
+	return building_def, origin, info.rotation
+end
+
 function building_lib.get_building_size(building_def, rotation)
 	local placement = building_lib.get_placement(building_def.placement)
 	return placement.get_size(placement, nil, building_def, rotation)

conditions.lua

@@ -115,12 +115,9 @@ end
 -- checks if a building with specified group is placed there already
 building_lib.register_condition("group", {
     can_build = function(mapblock_pos, value)
-		local building_info = building_lib.get_placed_building_info(mapblock_pos)
-		if building_info then
-			local building_def = building_lib.get_building(building_info.name)
-			if building_def and building_def.groups and building_def.groups[value] then
-				return true
-			end
+		local building_def = building_lib.get_building_def_at(mapblock_pos)
+		if building_def and building_def.groups and building_def.groups[value] then
+			return true
 		end
 		return false
 	end