Fix restore of banner desc after anvil rename

mods/ITEMS/mcl_anvils/init.lua

@@ -129,8 +129,16 @@ local function update_anvil_slots(meta)
 			-- Don't rename if names are identical
 			if new_name ~= old_name then
 				-- Rename item
-				meta:set_string("description", new_name)
-				-- Double-save the name internally, too
+				if new_name == "" and name_item:get_definition()._mcl_generate_description then
+					-- _mcl_generate_description(itemstack): If defined, set custom item description of itemstack.
+					-- This function should be defined for items with an advanced description.
+					-- See mcl_banners for an example.
+					name_item:get_definition()._mcl_generate_description(name_item)
+				else
+					-- Set description
+					meta:set_string("description", new_name)
+				end
+				-- Save the raw name internally, too
 				meta:set_string("name", new_name)
 				new_output = name_item
 			elseif just_rename then

mods/ITEMS/mcl_banners/init.lua

@@ -302,6 +302,19 @@ for colorid, colortab in pairs(mcl_banners.colors) do
 
 			return itemstack
 		end,
+
+		_mcl_generate_description = function(itemstack)
+			local meta = itemstack:get_meta()
+			local layers_raw = meta:get_string("layers")
+			if not layers_raw then
+				return nil
+			end
+			local layers = minetest.deserialize(layers_raw)
+			local desc = itemstack:get_definition().description
+			local newdesc = mcl_banners.make_advanced_banner_description(desc, layers)
+			meta:set_string("description", newdesc)
+			return newdesc
+		end,
 	})
 
 	if minetest.get_modpath("mcl_core") and minetest.get_modpath("mcl_wool") then