Implement player attribute backend (#4155)

* This backend permit mods to store extra players attributes to a common interface.
* Add the obj:set_attribute(attr, value) Lua call
* Add the obj:get_attribute(attr) Lua call

Examples:
* player:set_attribute("home:home", "10,25,-78")
* player:get_attribute("default:mana")

Attributes are saved as a json in the player file in extended_attributes
key

They are saved only if a modification on the attributes occurs and loaded
when emergePlayer is called (they are attached to PlayerSAO).

1 files changed, 41 insertions, 0 deletions

diff --git a/src/script/lua_api/l_object.cpp b/src/script/lua_api/l_object.cpp
index be4451704..9352812ab 100644
--- a/src/script/lua_api/l_object.cpp
+++ b/src/script/lua_api/l_object.cpp
@@ -1181,6 +1181,45 @@ int ObjectRef::l_get_breath(lua_State *L)
 	return 1;
 }
 
+// set_attribute(self, attribute, value)
+int ObjectRef::l_set_attribute(lua_State *L)
+{
+	ObjectRef *ref = checkobject(L, 1);
+	PlayerSAO* co = getplayersao(ref);
+	if (co == NULL) {
+		return 0;
+	}
+
+	std::string attr = luaL_checkstring(L, 2);
+	std::string value = luaL_checkstring(L, 3);
+
+	if (co->getType() == ACTIVEOBJECT_TYPE_PLAYER) {
+		co->setExtendedAttribute(attr, value);
+	}
+	return 1;
+}
+
+// get_attribute(self, attribute)
+int ObjectRef::l_get_attribute(lua_State *L)
+{
+	ObjectRef *ref = checkobject(L, 1);
+	PlayerSAO* co = getplayersao(ref);
+	if (co == NULL) {
+		return 0;
+	}
+
+	std::string attr = luaL_checkstring(L, 2);
+
+	std::string value = "";
+	if (co->getExtendedAttribute(attr, &value)) {
+		lua_pushstring(L, value.c_str());
+		return 1;
+	}
+
+	return 0;
+}
+
+
 // set_inventory_formspec(self, formspec)
 int ObjectRef::l_set_inventory_formspec(lua_State *L)
 {
@@ -1839,6 +1878,8 @@ const luaL_reg ObjectRef::methods[] = {
 	luamethod(ObjectRef, set_look_pitch),
 	luamethod(ObjectRef, get_breath),
 	luamethod(ObjectRef, set_breath),
+	luamethod(ObjectRef, get_attribute),
+	luamethod(ObjectRef, set_attribute),
 	luamethod(ObjectRef, set_inventory_formspec),
 	luamethod(ObjectRef, get_inventory_formspec),
 	luamethod(ObjectRef, get_player_control),