Player attrs: permits to remove an attribute by setting value to nil (#5716)

* Player attrs: permits to remove an attribute by setting value to nil

When doing player:set_attribute("attr", nil) remove attribute

Also remove a useless check on C++ API part (already done by checkplayer)

Fix #5709

doc/lua_api.txt

@@ -3028,7 +3028,9 @@ This is basically a reference to a C++ `ServerActiveObject`
         * `0`: player is drowning,
         * `1`-`10`: remaining number of bubbles
         * `11`: bubbles bar is not shown
-* `set_attribute(attribute, value)`: sets an extra attribute with value on player
+* `set_attribute(attribute, value)`:
+    * Sets an extra attribute with value on player.
+    * If value is nil, remove attribute from player.
 * `get_attribute(attribute)`: returns value for extra attribute. Returns nil if no attribute found.
 * `set_inventory_formspec(formspec)`
     * Redefine player's inventory form

games/minimal/mods/default/init.lua

@@ -18,6 +18,8 @@ dofile(minetest.get_modpath("default").."/mapgen.lua")
 minetest.register_on_joinplayer(function(player)
 	local cb = function(player)
 		minetest.chat_send_player(player:get_player_name(), "This is the [minimal] \"Minimal Development Test\" game. Use [minetest_game] for the real thing.")
+		player:set_attribute("test_attribute", "test_me")
+		player:set_attribute("remove_this", nil)
 	end
 	minetest.after(2.0, cb, player)
 end)
@@ -1387,13 +1389,13 @@ minetest.register_abm({
 
 		local srclist = inv:get_list("src")
 		local cooked = nil
-		
+
 		if srclist then
 			cooked = minetest.get_craft_result({method = "cooking", width = 1, items = srclist})
 		end
-		
+
 		local was_active = false
-		
+
 		if meta:get_float("fuel_time") < meta:get_float("fuel_totaltime") then
 			was_active = true
 			meta:set_float("fuel_time", meta:get_float("fuel_time") + 1)
@@ -1413,7 +1415,7 @@ minetest.register_abm({
 				meta:set_string("src_time", 0)
 			end
 		end
-		
+
 		if meta:get_float("fuel_time") < meta:get_float("fuel_totaltime") then
 			local percent = math.floor(meta:get_float("fuel_time") /
 					meta:get_float("fuel_totaltime") * 100)
@@ -1438,7 +1440,7 @@ minetest.register_abm({
 		local cooked = nil
 		local fuellist = inv:get_list("fuel")
 		local srclist = inv:get_list("src")
-		
+
 		if srclist then
 			cooked = minetest.get_craft_result({method = "cooking", width = 1, items = srclist})
 		end
@@ -1464,7 +1466,7 @@ minetest.register_abm({
 
 		meta:set_string("fuel_totaltime", fuel.time)
 		meta:set_string("fuel_time", 0)
-		
+
 		local stack = inv:get_stack("fuel", 1)
 		stack:take_item()
 		inv:set_stack("fuel", 1, stack)
@@ -1571,7 +1573,7 @@ function default.grow_tree(data, a, pos, is_apple_tree, seed)
 	y = y+th-1 -- (x, y, z) is now last piece of trunk
 	local leaves_a = VoxelArea:new{MinEdge={x=-2, y=-1, z=-2}, MaxEdge={x=2, y=2, z=2}}
 	local leaves_buffer = {}
-	
+
 	-- Force leaves near the trunk
 	local d = 1
 	for xi = -d, d do
@@ -1581,14 +1583,14 @@ function default.grow_tree(data, a, pos, is_apple_tree, seed)
 	end
 	end
 	end
-	
+
 	-- Add leaves randomly
 	for iii = 1, 8 do
 		local d = 1
 		local xx = pr:next(leaves_a.MinEdge.x, leaves_a.MaxEdge.x - d)
 		local yy = pr:next(leaves_a.MinEdge.y, leaves_a.MaxEdge.y - d)
 		local zz = pr:next(leaves_a.MinEdge.z, leaves_a.MaxEdge.z - d)
-		
+
 		for xi = 0, d do
 		for yi = 0, d do
 		for zi = 0, d do
@@ -1597,7 +1599,7 @@ function default.grow_tree(data, a, pos, is_apple_tree, seed)
 		end
 		end
 	end
-	
+
 	-- Add the leaves
 	for xi = leaves_a.MinEdge.x, leaves_a.MaxEdge.x do
 	for yi = leaves_a.MinEdge.y, leaves_a.MaxEdge.y do

src/content_sao.h

@@ -277,6 +277,16 @@ public:
 		return true;
 	}
 
+	inline void removeExtendedAttribute(const std::string &attr)
+	{
+		PlayerAttributes::iterator it = m_extra_attributes.find(attr);
+		if (it == m_extra_attributes.end())
+			return;
+
+		m_extra_attributes.erase(it);
+		m_extended_attributes_modified = true;
+	}
+
 	inline const PlayerAttributes &getExtendedAttributes()
 	{
 		return m_extra_attributes;

src/script/lua_api/l_object.cpp

@@ -1202,9 +1202,10 @@ int ObjectRef::l_set_attribute(lua_State *L)
 	}
 
 	std::string attr = luaL_checkstring(L, 2);
-	std::string value = luaL_checkstring(L, 3);
+	if (lua_isnil(L, 3)) {
-
+		co->removeExtendedAttribute(attr);
-	if (co->getType() == ACTIVEOBJECT_TYPE_PLAYER) {
+	} else {
+		std::string value = luaL_checkstring(L, 3);
 		co->setExtendedAttribute(attr, value);
 	}
 	return 1;