build_over fix and tests

build.lua

@@ -35,15 +35,14 @@ function building_lib.can_build(mapblock_pos, _, building_name, rotation)
 		return false, message or "size check '" .. building_def.placement .. "' failed"
 	end
 
+	-- true if the existing building can be built over
+	local build_over_mode = false
+
 	-- check if we can build over other buildings
 	if building_def.build_over then
 		local other_building_info, origin = building_lib.get_placed_building_info(mapblock_pos)
 		if other_building_info then
 			-- other building exists, check if it matches
-			if not vector.equals(other_building_info.size or {x=1,y=1,z=1}, size) then
-				return false, "Existing building has different size"
-			end
-
 			if not vector.equals(origin, mapblock_pos) then
 				return false, "Placement-origin mismatch"
 			end
@@ -74,8 +73,9 @@ function building_lib.can_build(mapblock_pos, _, building_name, rotation)
 
 			if not matches then
 				-- can't build over pointed building
-				-- TODO: proper pointed position
 				return false, "Existing building can't be built over"
+			else
+				build_over_mode = true
 			end
 		end
 	end
@@ -87,9 +87,12 @@ function building_lib.can_build(mapblock_pos, _, building_name, rotation)
 			break
 		end
 
-		local is_free = check_free(offset_mapblock_pos)
+		if not build_over_mode then
-		if not is_free then
+			-- check if the area is free
-			return false, "Space already occupied at " .. minetest.pos_to_string(offset_mapblock_pos)
+			local is_free = check_free(offset_mapblock_pos)
+			if not is_free then
+				return false, "Space already occupied at " .. minetest.pos_to_string(offset_mapblock_pos)
+			end
 		end
 
 		local success

build.spec.lua

@@ -9,6 +9,13 @@ building_lib.register_building("building_lib:dummy", {
 	placement = "dummy"
 })
 
+building_lib.register_building("building_lib:dummy_v2", {
+	placement = "dummy",
+    build_over = {
+        names = {"building_lib:dummy"}
+    }
+})
+
 mtt.register("build", function(callback)
     local mapblock_pos = {x=0, y=0, z=0}
     local building_name = "building_lib:dummy"
@@ -34,6 +41,11 @@ mtt.register("build", function(callback)
     assert(err)
     assert(not success)
 
+    -- try to build over with v2 building
+    success, err = building_lib.can_build(mapblock_pos, playername, building_name .. "_v2", rotation)
+    assert(not err, err)
+    assert(success)
+
     -- check
     local info = building_lib.get_placed_building_info(mapblock_pos)
     assert(info.name == building_name)

tools.lua

@@ -91,6 +91,14 @@ minetest.register_tool("building_lib:place", {
     on_step = function(itemstack, player)
         local playername = player:get_player_name()
         local mapblock_pos1 = building_lib.get_pointed_mapblock(player)
+        local rotation = building_lib.get_build_rotation(player)
+
+        local placed_building_info, placed_building_origin = building_lib.get_placed_building_info(mapblock_pos1)
+        if placed_building_info then
+            -- use origin and rotation of existing pointed-at building
+            mapblock_pos1 = placed_building_origin
+            rotation = placed_building_info.rotation
+        end
 
         local meta = itemstack:get_meta()
         local buildingname = meta:get_string("buildingname")
@@ -100,7 +108,6 @@ minetest.register_tool("building_lib:place", {
             return
         end
 
-        local rotation = building_lib.get_build_rotation(player)
         local size = building_lib.get_building_size(building_def, rotation)
         local mapblock_pos2 = vector.add(mapblock_pos1, vector.subtract(size, 1))