Add ObjRef:is_player() and modify ObjRef:get_player_name() to always return a string to aid better inter-object compatibility of code that assumes objects to be players

builtin/misc.lua

@@ -44,7 +44,7 @@ function minetest.get_connected_players()
 	-- This could be optimized a bit, but leave that for later
 	local list = {}
 	for _, obj in pairs(minetest.env:get_objects_inside_radius({x=0,y=0,z=0}, 1000000)) do
-		if obj:get_player_name() then
+		if obj:is_player() then
 			table.insert(list, obj)
 		end
 	end

doc/lua_api.txt

@@ -913,7 +913,8 @@ LuaEntitySAO-only: (no-op for other objects)
 - get_entity_name() (DEPRECATED: Will be removed in a future version)
 - get_luaentity()
 Player-only: (no-op for other objects)
-- get_player_name(): will return nil if is not a player
+- is_player(): true for players, false for others
+- get_player_name(): returns "" if is not a player
 - get_look_dir(): get camera direction as a unit vector
 - get_look_pitch(): pitch in radians
 - get_look_yaw(): yaw in radians (wraps around pretty randomly as of now)

src/scriptapi.cpp

@@ -2683,6 +2683,15 @@ private:
 	}
 	
 	/* Player-only */
+
+	// is_player(self)
+	static int l_is_player(lua_State *L)
+	{
+		ObjectRef *ref = checkobject(L, 1);
+		Player *player = getplayer(ref);
+		lua_pushboolean(L, (player != NULL));
+		return 1;
+	}
 	
 	// get_player_name(self)
 	static int l_get_player_name(lua_State *L)
@@ -2690,7 +2699,7 @@ private:
 		ObjectRef *ref = checkobject(L, 1);
 		Player *player = getplayer(ref);
 		if(player == NULL){
-			lua_pushnil(L);
+			lua_pushlstring(L, "", 0);
 			return 1;
 		}
 		// Do it