Checks players’ inventory for undiscovered recipes

When the player joins, check their inventory — this
will unlock recipes even if this mod is run for the
first time in a pre-existing world.

init.lua

@@ -540,6 +540,17 @@ minetest.register_on_craft(function(itemstack, player)
 		update_known_items(player, itemstack:get_name())
 end)
 
+-- Go over all items in the player’s inventory for undiscovered recipes.
+function check_player_inventory(player)
+	local inv = player:get_inventory(player)
+	local items = inv:get_list("main")
+	if items then
+		for _,stack in pairs(items) do
+			update_known_items(player, stack:get_name())
+		end
+	end
+end
+
 -- Initialize player-data.
 -- If saved data is found, load previous held-items and held-groups data.
 function load_player_data(player)
@@ -601,6 +612,7 @@ end
 minetest.register_on_joinplayer(function(player)
 	load_player_data(player)
 	init_player_known_items(player)
+	check_player_inventory(player)
 
 	-- Init displayed items.
 	local data = player_data[player:get_player_name()]