fix recipe util function, print message if recipes are not added

util.lua

 
+kif.get_item_name_from_string = function(str)
+	local space = string.find(str, ' ')
+	if space == nil then
+		return str
+	else
+		return string.sub(str, 1, space-1)
+	end
+end
+
+kif.is_group_string = function(str)
+	local group = 'group:'
+	if string.sub(str, 1, #group) == group then
+		return string.sub(str, #group+1)
+	else
+		return false
+	end
+end
+
+
+local debug = function(msg, item)
+	if item == nil then
+		item = ''
+	else
+		item = " " .. kif.get_item_name_from_string(tostring(item))
+	end
+	print("kif.register_craft_if_items_exist() "..msg..item)
+end
+
+
+kif.discovered_item_groups = {}
+
+kif.group_exists = function(group)
+	-- all desired items have to have been registered already to discover their groups (obviously)
+	-- you might need to include these mods as optional dependencies
+	if kif.discovered_item_groups[group] == group then
+		return true
+	end
+
+	for name, item in pairs(minetest.registered_items) do
+		if type(item.groups) == "table" then
+			for group, rating in pairs(item.groups) do
+				kif.discovered_item_groups[group] = group
+			end
+		end
+		if kif.discovered_item_groups[group] == group then
+			local n = 0
+			for k,v in pairs(kif.discovered_item_groups) do
+				n = n+1
+			end
+			return true
+		end
+	end
+	return false
+end
+
+
 kif.register_craft_if_items_exist = function(def)
-	if def.output and minetest.registered_items[tostring(def.output)] == nil then
+	if def.output and minetest.registered_items[kif.get_item_name_from_string(def.output)] == nil then
+		debug("[FAIL] unknown output", def.output)
 		return false
 	end
 	if def.recipe then
 		if type(def.recipe) ~= "table" then
-			if minetest.registered_items[tostring(def.recipe)] == nil then
+			local recipe_item = kif.get_item_name_from_string(def.recipe)
+			if minetest.registered_items[recipe_item] == nil then
+				local group = kif.is_group_string(recipe_item)
+				if not (group and kif.group_exists(group)) then
+					debug("[FAIL] unknown recipe", recipe_item)
 					return false
 				end
+			end
 		else
 			for y, row in ipairs(def.recipe) do
 				if type(row) ~= "table" then
-					if row ~= "" and minetest.registered_items[tostring(row)] == nil then
+					local row_item = kif.get_item_name_from_string(row)
+					if minetest.registered_items[row_item] == nil then
+						local group = kif.is_group_string(row_item)
+						if not (group and kif.group_exists(group)) then
+							debug("[FAIL] unknown row item", row_item)
 							return false
 						end
+					end
 				else
 					for x, col in ipairs(row) do
-						if col ~= "" and minetest.registered_items[tostring(col)] == nil then
+						local col_item = kif.get_item_name_from_string(col)
+						if col ~= "" and minetest.registered_items[col_item] == nil then
+							local group = kif.is_group_string(col_item)
+							if not (group and kif.group_exists(group)) then
+								debug("[FAIL] unknown item", col)
 								return false
 							end
 						end
 					end
 				end
 			end
+		end
 		-- still here? recipe is fine then!
 		minetest.register_craft(def)
 		return true