New [remove_object] WML tag

changelog

@@ -18,9 +18,19 @@ Version 1.13.5+dev:
    * [modify_unit] now understands [effect] tags, which it applies directly.
      This replaces the use of [object] with no_write=yes (which will be removed
      in the next release).
+   * Add [object]take_only_once=yes|no (default yes) - if set to no, automatic
+     tracking is disabled for this object (allowing it to be taken multiple times
+     even if it has an id).
+   * New [remove_object] tag which removes applied [object]s from matched units;
+     it can filter on the entire [object] WML. The most efficient use is to
+     remove all objects with a specific duration value.
  * Lua API:
    * Added new functions wesnoth.fire_event_by_id and fire_event_by_name. The old
      function wesnoth.fire_event is now an alias for wesnoth.fire_event_by_name
+   * Added new function wesnoth.remove_modifications, which removes applied
+     modifications of the chosen type from a unit. The most efficient use is to
+     remove all modifications with a specific duration value.
+     Also callable as u:remove_modifications.
 * Performance:
    * When a heuristic determines that it's probably faster, the game predicts battle
      outcome by simulating a few thousand fights instead of calculating exact

data/lua/wml/object.lua

@@ -10,8 +10,10 @@ function wml_actions.object(cfg)
 	local context = wesnoth.current.event_context
 
 	-- If this item has already been used
+	local unique = cfg.take_only_once
+	if unique == nil then unique = true end
 	local obj_id = utils.check_key(cfg.id, "id", "object", true)
-	if obj_id and used_items[obj_id] then return end
+	if obj_id and unique and used_items[obj_id] then return end
 
 	local unit, command_type, text
 
@@ -43,7 +45,7 @@ function wml_actions.object(cfg)
 		wesnoth.highlight_hex(unit.x, unit.y)
 
 		-- Mark this item as used up
-		if obj_id then used_items[obj_id] = true end
+		if obj_id and unique then used_items[obj_id] = true end
 	else
 		text = tostring(cfg.cannot_use_message or "")
 		command_type = "else"
@@ -86,6 +88,13 @@ function wesnoth.game_events.on_save()
 	return cfg
 end
 
+function wml_actions.remove_object(cfg)
+	local obj_id = cfg.object_id
+	for _,unit in ipairs(wesnoth.get_units(cfg)) do
+		wesnoth.remove_modifications(unit, {id = obj_id})
+	end
+end
+
 function wesnoth.wml_conditionals.found_item(cfg)
 	return used_items[utils.check_key(cfg.id, "id", "found_item", true)]
 end

src/scripting/game_lua_kernel.cpp

@@ -3622,6 +3622,32 @@ static int intf_add_modification(lua_State *L)
 	return 0;
 }
 
+/**
+ * Removes modifications from a unit
+ * - Arg 1: unit
+ * - Arg 2: table (filter as [filter_wml])
+ * - Arg 3: type of modification (default "object")
+ */
+static int intf_remove_modifications(lua_State *L)
+{
+	unit& u = luaW_checkunit(L, 1);
+	config filter = luaW_checkconfig(L, 2);
+	std::string tag = luaL_optstring(L, 3, "object");
+	config::const_attr_itors ai = filter.attribute_range();
+	config::all_children_itors ci = filter.all_children_range();
+	if(std::distance(ai.first, ai.second) == 1 && std::distance(ci.first, ci.second) == 0 && ai.first->first == "duration") {
+		u.expire_modifications(filter["duration"]);
+	} else {
+		for(config& obj : u.get_modifications().child_range(tag)) {
+			if(obj.matches(filter)) {
+				obj["duration"] = "now";
+			}
+		}
+		u.expire_modifications("now");
+	}
+	return 0;
+}
+
 /**
  * Advances a unit if the unit has enough xp.
  * - Arg 1: unit.
@@ -4617,6 +4643,7 @@ game_lua_kernel::game_lua_kernel(CVideo * video, game_state & gs, play_controlle
 		{ "get_traits",               &intf_get_traits               },
 		{ "get_viewing_side",         &intf_get_viewing_side         },
 		{ "modify_ai",                &intf_modify_ai                },
+		{ "remove_modifications",     &intf_remove_modifications     },
 		{ "set_music",                &intf_set_music                },
 		{ "transform_unit",           &intf_transform_unit           },
 		{ "unit_ability",             &intf_unit_ability             },
@@ -4985,6 +5012,7 @@ int game_lua_kernel::return_unit_method(lua_State *L, char const *m) {
 		{"extract",               &dispatch<&game_lua_kernel::intf_extract_unit>},
 		{"advance",               intf_advance_unit},
 		{"add_modification",      intf_add_modification},
+		{"remove_modifications",  intf_remove_modifications},
 		{"resistance",            intf_unit_resistance},
 		{"defense",               intf_unit_defense},
 		{"movement",              intf_unit_movement_cost},

src/units/unit.hpp

@@ -317,6 +317,7 @@ public:
 	std::vector<std::pair<std::string,std::string> > amla_icons() const;
 
 	std::vector<config> get_modification_advances() const;
+	config& get_modifications() { return modifications_; }
 
 	typedef boost::ptr_vector<config> t_advancements;
 	void set_advancements(std::vector<config> advancements);