Merge aa5d8aee1e into fdc149f316

builtin/common/metatable.lua

@@ -1,14 +1,28 @@
 -- Registered metatables, used by the C++ packer
+local serializable_metatables = {}
 local known_metatables = {}
-function core.register_portable_metatable(name, mt)
+
+local function dummy_serializer(x)
+	return x
+end
+
+function core.register_portable_metatable(name, mt, serializer, deserializer)
+	serializer = serializer or dummy_serializer
+	deserializer = deserializer or function(x) return setmetatable(x, mt) end
 	assert(type(name) == "string", ("attempt to use %s value as metatable name"):format(type(name)))
 	assert(type(mt) == "table", ("attempt to register a %s value as metatable"):format(type(mt)))
+	assert(type(serializer), ("attempt to use a %s value as serializer"):format(type(serializer)))
+	assert(type(deserializer), ("attempt to use a %s value as serialier"):format(type(deserializer)))
 	assert(known_metatables[name] == nil or known_metatables[name] == mt,
 			("attempt to override metatable %s"):format(name))
 	known_metatables[name] = mt
 	known_metatables[mt] = name
+	serializable_metatables[mt] = serializer
+	serializable_metatables[name] = deserializer
 end
+
 core.known_metatables = known_metatables
+core.serializable_metatables = serializable_metatables
 
 function core.register_async_metatable(...)
 	core.log("deprecated", "core.register_async_metatable is deprecated. " ..
@@ -17,3 +31,9 @@ function core.register_async_metatable(...)
 end
 
 core.register_portable_metatable("__builtin:vector", vector.metatable)
+
+if ItemStack then
+	local item = ItemStack()
+	local itemstack_mt = getmetatable(item)
+	core.register_portable_metatable("__itemstack", itemstack_mt, item.to_table, ItemStack)
+end

builtin/common/serialize.lua

@@ -8,22 +8,38 @@ local next, rawget, pairs, pcall, error, type, setfenv, loadstring
 local table_concat, string_dump, string_format, string_match, math_huge
 	= table.concat, string.dump, string.format, string.match, math.huge
 
--- Recursively counts occurrences of objects (non-primitives including strings) in a table.
-local function count_objects(value)
+local function pack_args(...)
+	return {n = select("#", ...), ...}
+end
+
+-- Recursively
+-- (1) reads metatables from tables;
+-- (2) counts occurrences of objects (non-primitives including strings) in a table.
+local function prepare_objects(value)
 	local counts = {}
+	local type_lookup = {}
 	if value == nil then
 		-- Early return for nil; tables can't contain nil
-		return counts
+		return counts, type_lookup
 	end
-	local function count_values(val)
+	local function count_values(val, recount)
 		local type_ = type(val)
 		if type_ == "boolean" or type_ == "number" then
 			return
 		end
 		local count = counts[val]
-		counts[val] = (count or 0) + 1
-		if type_ == "table" then
-			if not count then
+		if not recount then
+			counts[val] = (count or 0) + 1
+		end
+		local mt = (not count) and (type_ == "table" or type_ == "userdata") and getmetatable(val)
+		if mt and core.serializable_metatables[mt] then
+			local args = pack_args(core.known_metatables[mt], core.serializable_metatables[mt](val))
+			type_lookup[val] = args
+			for _, v in ipairs(args) do
+				count_values(v, rawequal(v, val))
+			end
+		elseif type_ == "table" then
+			if recount or not count then
 				for k, v in pairs(val) do
 					count_values(k)
 					count_values(v)
@@ -34,7 +50,7 @@ local function count_objects(value)
 		end
 	end
 	count_values(value)
-	return counts
+	return counts, type_lookup
 end
 
 -- Build a "set" of Lua keywords. These can't be used as short key names.
@@ -66,7 +82,15 @@ local function serialize(value, write)
 	local references = {}
 	-- Circular tables that must be filled using `table[key] = value` statements
 	local to_fill = {}
-	for object, count in pairs(count_objects(value)) do
+	local counts, typeinfo = prepare_objects(value)
+	if next(typeinfo) then
+		write [[
+		if not (core and core.serializable_metatables) then
+			core = { known_metatables = {}, serializable_metatables = {}}
+		end;
+		]]
+	end
+	for object, count in pairs(counts) do
 		local type_ = type(object)
 		-- Object must appear more than once. If it is a string, the reference has to be shorter than the string.
 		if count >= 2 and (type_ ~= "string" or #reference + 5 < #object) then
@@ -96,7 +120,22 @@ local function serialize(value, write)
 	local function use_short_key(key)
 		return not references[key] and type(key) == "string" and (not keywords[key]) and string_match(key, "^[%a_][%a%d_]*$")
 	end
-	local function dump(value)
+	local dump
+	local function dump_serialized(value)
+		local serialized = assert(typeinfo[value])
+		write "(core.serializable_metatables["
+		dump(serialized[1])
+		write "])("
+		for k = 2, serialized.n do
+			if k ~= 2 then
+				write ","
+			end
+			local v = serialized[k]
+			dump(v, rawequal(v, value))
+		end
+		write ")"
+	end
+	dump = function(value, skip_mt)
 		-- Primitive types
 		if value == nil then
 			return write("nil")
@@ -126,6 +165,10 @@ local function serialize(value, write)
 			write(ref)
 			return write"]"
 		end
+		if (not skip_mt) and typeinfo[value] then
+			dump_serialized(value)
+			return
+		end
 		if type_ == "string" then
 			return write(quote(value))
 		end
@@ -168,8 +211,8 @@ local function serialize(value, write)
 		end
 	end
 	-- Write the statements to fill circular tables
-	for table, ref in pairs(to_fill) do
-		for k, v in pairs(table) do
+	for tbl, ref in pairs(to_fill) do
+		for k, v in pairs(tbl) do
 			write("_[")
 			write(ref)
 			write("]")
@@ -185,6 +228,13 @@ local function serialize(value, write)
 			dump(v)
 			write(";")
 		end
+		if typeinfo[tbl] then
+			write("_[")
+			write(ref)
+			write("]=")
+			dump_serialized(tbl)
+			write(";")
+		end
 	end
 	write("return ")
 	dump(value)
@@ -246,7 +296,14 @@ function core.deserialize(str, safe)
 	if not func then return nil, err end
 
 	-- math.huge was serialized to inf and NaNs to nan by Lua in engine version 5.6, so we have to support this here
-	local env = {inf = math_huge, nan = 0/0}
+	local env = {
+		inf = math_huge,
+		nan = 0/0,
+		core = {
+			known_metatables = core.known_metatables,
+			serializable_metatables = core.serializable_metatables,
+		},
+	}
 	if safe then
 		env.loadstring = dummy_func
 	else
@@ -266,3 +323,4 @@ function core.deserialize(str, safe)
 	end
 	return nil, value_or_err
 end
+

builtin/common/tests/serialize_spec.lua

@@ -4,6 +4,7 @@ _G.setfenv = require 'busted.compatibility'.setfenv
 
 dofile("builtin/common/serialize.lua")
 dofile("builtin/common/vector.lua")
+dofile("builtin/common/metatable.lua")
 
 -- Supports circular tables; does not support table keys
 -- Correctly checks whether a mapping of references ("same") exists
@@ -40,11 +41,32 @@ local t1, t2 = {x, x, y, y}, {x, y, x, y}
 assert.same(t1, t2) -- will succeed because it only checks whether the depths match
 assert(not pcall(assert_same, t1, t2)) -- will correctly fail because it checks whether the refs match
 
+local pair_mt = {
+	__eq = function(x, y)
+		return x[1] == y[1] and x[2] == y[2]
+	end,
+}
+local function pair(x, y)
+	return setmetatable({x, y}, pair_mt)
+end
+-- Use our own serialization functions to avoid incorrectly passing test related to references.
+core.register_portable_metatable("pair", pair_mt)
+assert.equals(pair(1, 2), pair(1, 2))
+assert.not_equals(pair(1, 2), pair(3, 4))
+
 describe("serialize", function()
 	local function assert_preserves(value)
 		local preserved_value = core.deserialize(core.serialize(value))
 		assert_same(value, preserved_value)
 	end
+	local function assert_strictly_preserves(value)
+		local preserved_value = core.deserialize(core.serialize(value))
+		assert.equals(value, preserved_value)
+	end
+	local function assert_compatibly_preserves(value)
+		local preserved_value = loadstring(core.serialize(value))()
+		assert_same(value, preserved_value)
+	end
 	it("works", function()
 		assert_preserves({cat={sound="nyan", speed=400}, dog={sound="woof"}})
 	end)
@@ -53,6 +75,10 @@ describe("serialize", function()
 		assert_preserves({escape_chars="\n\r\t\v\\\"\'", non_european="θשׁ٩∂"})
 	end)
 
+	it("handles nil", function()
+		assert_strictly_preserves(nil)
+	end)
+
 	it("handles NaN & infinities", function()
 		local nan = core.deserialize(core.serialize(0/0))
 		assert(nan ~= nan)
@@ -141,7 +167,10 @@ describe("serialize", function()
 	it("vectors work", function()
 		local v = vector.new(1, 2, 3)
 		assert_preserves({v})
-		assert_preserves(v)
+		assert_compatibly_preserves({v})
+		assert_strictly_preserves(v)
+		assert_compatibly_preserves(v)
+		assert(core.deserialize(core.serialize(v)):check())
 
 		-- abuse
 		v = vector.new(1, 2, 3)
@@ -149,6 +178,43 @@ describe("serialize", function()
 		assert_preserves(v)
 	end)
 
+	it("correctly handles typed objects with multiple references", function()
+		local x, y = pair(1, 2), pair(1, 2)
+		local t = core.deserialize(core.serialize{x, x, y})
+		assert.equals(x, t[1])
+		assert.equals(x, t[3])
+		assert(rawequal(t[1], t[2]))
+		assert(not rawequal(t[1], t[3]))
+	end)
+
+	it("correctly handles recursive typed objects with the identity function as serializer", function()
+		local mt = {
+			__eq = function(x, y)
+				return x[1] == y[1]
+			end,
+		}
+		core.register_portable_metatable("test_recursive_typed", mt)
+		local t = setmetatable({1}, mt)
+		t[2] = t
+		assert_strictly_preserves(t)
+	end)
+
+	it("correctly handles binary trees", function()
+		local child = {pair(1, 1)}
+		local layers = 4
+		for i = 2, layers do
+			child[i] = pair(child[i-1], child[i-1])
+		end
+		local tree = child[layers]
+		assert_strictly_preserves(tree)
+		local node = core.deserialize(core.serialize(tree))
+		for i = 2, layers do
+			assert(rawequal(node[1], node[2]))
+			node = node[1]
+		end
+		assert_compatibly_preserves(tree)
+	end)
+
 	it("handles keywords as keys", function()
 		assert_preserves({["and"] = "keyword", ["for"] = "keyword"})
 	end)

builtin/common/vector.lua

@@ -12,6 +12,10 @@ vector = {}
 local metatable = {}
 vector.metatable = metatable
 
+if core and core.register_serializable then
+	core.register_serializable("__builtin:vector", metatable)
+end
+
 local xyz = {"x", "y", "z"}
 
 -- only called when rawget(v, key) returns nil

doc/lua_api.md

@@ -7812,12 +7812,18 @@ Misc.
 * `core.global_exists(name)`
     * Checks if a global variable has been set, without triggering a warning.
 
-* `core.register_portable_metatable(name, mt)`:
+* `core.register_portable_metatable(name, mt, serializer, deserializer)`:
     * Register a metatable that should be preserved when Lua data is transferred
-      between environments (via IPC or `handle_async`).
+      between environments (via IPC, `handle_async`, or `core.serialize`).
     * `name` is a string that identifies the metatable. It is recommended to
       follow the `modname:name` convention for this identifier.
     * `mt` is the metatable to register.
+    * `serializer` is a function used by `core.serialize` to serialize data with
+      the given metatable. It may return multiple values, but the return values should not
+      contain the input datum unless `serializer` is the identity function. The default
+      value for `serializer` is the identity function.
+    * `deserializer` is a function used by `core.deserialize` to deserialize data from
+      values returned by `serializer`. The default value is a wrapper around `setmetatable`.
     * Note that the same metatable can be registered under multiple names,
       but multiple metatables must not be registered under the same name.
     * You must register the metatable in both the main environment

games/devtest/mods/unittests/itemstack_equals.lua

@@ -72,3 +72,10 @@ local function test_itemstack_equals_metadata()
 end
 
 unittests.register("test_itemstack_equals_metadata", test_itemstack_equals_metadata)
+
+local function test_itemstack_serialization_preservation()
+	local i = ItemStack("basenodes:stone 20 1000")
+	assert(i:equals(core.deserialize(core.serialize(i))))
+end
+
+unittests.register("test_itemstack_serialization_preservation", test_itemstack_serialization_preservation)