Factorio script for assemblers with unchangeable recipe

control.lua

script.on_init(function()
	global.open_assemblers = global.open_assemblers or {}
end)

script.on_event(defines.events.on_gui_opened, function(event)
	if event.entity and event.entity.name == 'assembling-machine-3' then
		global.open_assemblers[event.entity.unit_number] = global.open_assemblers[event.entity.unit_number] or {
			entity = event.entity,
			recipe = event.entity.get_recipe(),
			players = {},
		}
		global.open_assemblers[event.entity.unit_number].players[event.player_index] = true
	end
end)

script.on_event(defines.events.on_tick, function(event)
	for _, assembler in pairs(global.open_assemblers) do
		assembler.entity.set_recipe(assembler.recipe)
	end
end)

script.on_event(defines.events.on_gui_closed, function(event)
	for unit_number, assembler in pairs(global.open_assemblers) do
		for player_index, _ in pairs(assembler.players) do
			local player = game.players[player_index]
			if not player.opened or player.opened.unit_number ~= unit_number then
				assembler.players[player_index] = nil
			end
			if next(assembler.players) == nil then
				global.open_assemblers[unit_number] = nil
			end
		end
	end
end)