Add Lua "Persistent Object" Serialization

data/libs/CommodityType.lua

@@ -100,8 +100,12 @@ CommodityType.registry = {}
 function CommodityType.RegisterCommodity(name, info)
 	assert(not CommodityType.registry[name])
 
-	CommodityType.registry[name] = CommodityType.New(name, info)
-	return CommodityType.registry[name]
+	local commodity = CommodityType.New(name, info)
+
+	CommodityType.registry[name] = commodity
+	Serializer:RegisterPersistent("CommodityType." .. name, commodity)
+
+	return commodity
 end
 
 -- Function: GetCommodity
@@ -122,14 +126,14 @@ end
 -- Ensure loaded commodity types always point at the 'canonical' instance of the commodity;
 -- commodity types not defined by the current version of the code will be loaded verbatim
 function CommodityType.Unserialize(data)
-	local ct = CommodityType.GetCommodity(data.name)
+	setmetatable(data, CommodityType.meta)
 
-	if not ct then
+	if not CommodityType.registry[data.name] then
 		logWarning('Commodity type ' .. data.name .. ' could not be found, are you loading an outdated save?')
-		ct = CommodityType.RegisterCommodity(data.name, data)
+		CommodityType.registry[data.name] = data
 	end
 
-	return ct
+	return data
 end
 
 Serializer:RegisterClass('CommodityType', CommodityType)

data/meta/Serializer.lua

@@ -25,4 +25,11 @@ function Serializer:Register(key, serialize, unserialize) end
 ---@param class table
 function Serializer:RegisterClass(key, class) end
 
+-- Register a table as a "persistent" value. All references to the saved
+-- instance of that table will be transparently replaced across savegames to
+-- maintain table instance identity.
+---@param key string
+---@param value table
+function Serializer:RegisterPersistent(key, value) end
+
 return Serializer

data/modules/Debug/TestSerialization.lua

@@ -44,3 +44,33 @@ end
 Serializer:RegisterClass('TestClass', testClass)
 Serializer:Register('TestSerialization', serialize, unserialize)
 --]]
+
+--[[
+local persistentClass = utils.inherits(nil, 'TestClassPersistent')
+
+local persistentInstance = persistentClass.New()
+
+function persistentClass:Unserialize()
+	print("Unserialized a persistent object")
+
+	return setmetatable(self, persistentClass.meta)
+end
+
+Serializer:RegisterPersistent('TestPersistentObject', persistentInstance)
+
+local function serialize()
+	local test_data = {
+		instance = persistentInstance
+	}
+	return test_data
+end
+
+local function unserialize(data)
+	print(persistentInstance)
+	print(data.instance)
+	print(persistentInstance == data.instance)
+end
+
+Serializer:RegisterClass('TestClassPersistent', persistentClass)
+Serializer:Register('TestSerialization2', serialize, unserialize)
+--]]

src/Game.cpp

@@ -159,6 +159,7 @@ Game::Game(const Json &jsonObj) :
 
 	// Preparing the Lua stuff
 	Pi::luaSerializer->InitTableRefs();
+	Pi::luaSerializer->LoadPersistent(jsonObj);
 
 	GalacticEconomy::LoadFromJson(jsonObj);
 
@@ -214,6 +215,7 @@ void Game::ToJson(Json &jsonObj)
 	PROFILE_SCOPED()
 	// preparing the lua serializer
 	Pi::luaSerializer->InitTableRefs();
+	Pi::luaSerializer->SavePersistent(jsonObj);
 
 	// version
 	jsonObj["version"] = s_saveVersion;