metatables: feature to toggle (de)serializing them. Fix #21. (#22)

USAGE.md

@@ -7,6 +7,7 @@
     * [`bitser.loads`](#loads)
     * [`bitser.loadData`](#loaddata)
     * [`bitser.loadLoveFile`](#loadlovefile)
+    * [`bitser.includeMetatables`](#includeMetatables)
     * [`bitser.register`](#register)
     * [`bitser.registerClass`](#registerclass)
     * [`bitser.unregister`](#unregister)
@@ -148,6 +149,14 @@ Only useful if you're running [LÖVE](https://love2d.org/).
 
 See also: [`bitser.dumpLoveFile`](#dumplovefile).
 
+## includeMetatables
+
+Controls whether bitser will (de)serialize metatables. true by default.
+
+```lua
+bitser.includeMetatables(bool)
+```
+
 ## register
 
 ```lua

bitser.lua

@@ -30,6 +30,7 @@ local buf = nil
 local buf_is_writable = true
 local writable_buf = nil
 local writable_buf_size = nil
+local includeMetatables = true -- togglable with bitser.includeMetatables(false)
 local SEEN_LEN = {}
 
 local function Buffer_prereserve(min_size)
@@ -198,7 +199,7 @@ local function write_table(value, seen)
 		classkey = classkey_registry[classname]
 		Buffer_write_byte(242)
 		serialize_value(classname, seen)
-	elseif metatable then
+	elseif includeMetatables and metatable then
 		Buffer_write_byte(253)
 	else
 		Buffer_write_byte(240)
@@ -221,7 +222,7 @@ local function write_table(value, seen)
 			serialize_value(v, seen)
 		end
 	end
-	if metatable and not classname then
+	if includeMetatables and metatable and not classname then
 		serialize_value(metatable, seen)
 	end
 end
@@ -323,7 +324,9 @@ local function deserialize_value(seen)
 			v[key] = deserialize_value(seen)
 		end
 		if t == 253 then
-			setmetatable(v, deserialize_value(seen))
+			if includeMetatables then
+				setmetatable(v, deserialize_value(seen))
+			end
 		end
 		return v
 	elseif t == 241 then
@@ -434,6 +437,8 @@ end, loads = function(str)
 	end
 	Buffer_newReader(str)
 	return deserialize_value({})
+end, includeMetatables = function(bool)
+	includeMetatables = not not bool
 end, register = function(name, resource)
 	assert(not resource_registry[name], name .. " already registered")
 	resource_registry[name] = resource

spec/bitser_spec.lua

@@ -334,10 +334,18 @@ describe("bitser", function()
 	it("can read and write simple multiple cdata of the same ctype without getting confused", function()
 		test_serdeser({ffi.new('double', 42.5), ffi.new('double', 12), ffi.new('double', 0.01)})
 	end)
-	it("can read and write metatables", function()
+	it("can read and write metatables by default", function()
 		local t = setmetatable({foo="foo"}, {__index = {bar="bar"}})
 		test_serdeser(t)
 		assert.are.same(getmetatable(t), getmetatable(serdeser(t)))
 		assert.are.same(serdeser(t).bar, "bar")
 	end)
+	it("ignores metatables if the feature is explicitly disabled", function()
+		bitser.includeMetatables(false)
+		local t = setmetatable({foo="foo"}, {__index = {bar="bar"}})
+		test_serdeser(t)
+		assert.is_nil(getmetatable(serdeser(t)))
+		assert.is_nil(serdeser(t).bar)
+		bitser.includeMetatables(true) -- revert back to default for potential other tests
+	end)
 end)