Use to-be-closed variables to scope WML variables in tag definitions

data/lua/wml-flow.lua

@@ -111,7 +111,7 @@ wesnoth.wml_actions["for"] = function(cfg)
 		return
 	end
 	local i_var = cfg.variable or "i"
-	local save_i = utils.start_var_scope(i_var)
+	local save_i <close> = utils.scoped_var(i_var)
 	wml.variables[i_var] = first
 	local function loop_condition()
 		local sentinel = loop_lim.last
@@ -146,7 +146,6 @@ wesnoth.wml_actions["for"] = function(cfg)
 		wml.variables[i_var] = wml.variables[i_var] + loop_lim.step
 	end
 	::exit::
-	utils.end_var_scope(i_var, save_i)
 end
 
 wml_actions["repeat"] = function(cfg)
@@ -180,9 +179,9 @@ function wml_actions.foreach(cfg)
 	local array = wml.array_variables[array_name]
 	if #array == 0 then return end -- empty and scalars unwanted
 	local item_name = cfg.variable or "this_item"
-	local this_item = utils.start_var_scope(item_name) -- if this_item is already set
+	local this_item <close> = utils.scoped_var(item_name) -- if this_item is already set
 	local i_name = cfg.index_var or "i"
-	local i = utils.start_var_scope(i_name) -- if i is already set
+	local i <close> = utils.scoped_var(i_name) -- if i is already set
 	local array_length = wml.variables[array_name .. ".length"]
 
 	for index, value in ipairs(array) do
@@ -214,10 +213,6 @@ function wml_actions.foreach(cfg)
 	end
 	::exit::
 
-	-- house cleaning
-	utils.end_var_scope(item_name, this_item)
-	utils.end_var_scope(i_name, i)
-
 	--[[
 		This forces the readonly key to be taken literally.
 

data/lua/wml-utils.lua

@@ -182,8 +182,15 @@ function utils.end_var_scope(name, var)
 	end
 end
 
+function utils.scoped_var(name)
+	utils.start_var_scope(name)
+	return setmetatable({}, {__close = function() utils.end_var_scope(name) end})
+end
+
 utils.trim = wesnoth.deprecate_api('wml_utils.trim', 'stringx.trim', 1, nil, stringx.trim)
 utils.parenthetical_split = wesnoth.deprecate_api('wml_utils.parenthetical_split', 'stringx.quoted_split or stringx.split', 1, nil, utils.parenthetical_split)
 utils.split = wesnoth.deprecate_api('wml_utils.split', 'stringx.split', 1, nil, utils.split)
+utils.start_var_scope = wesnoth.deprecate_api('wml_utils.start_var_scope', 'wml_utils.scoped_var', 1, nil, utils.start_var_scope, 'Assign the scoped_var to a to-be-closed local variable.')
+utils.end_var_scope = wesnoth.deprecate_api('wml_utils.end_var_scope', 'wml_utils.scoped_var', 1, nil, utils.end_var_scope, 'Assign the scoped_var to a to-be-closed local variable.')
 
 return utils

data/lua/wml/find_path.lua

@@ -6,7 +6,7 @@ function wesnoth.wml_actions.find_path(cfg)
 	local unit = wesnoth.units.find_on_map(filter_unit)[1] or wml.error("[find_path]'s filter didn't match any unit")
 	local filter_location = wml.get_child(cfg, "destination") or wml.error( "[find_path] missing required [destination] tag" )
 	-- support for $this_unit
-	local this_unit = utils.start_var_scope("this_unit")
+	local this_unit <close> = utils.scoped_var("this_unit")
 
 	wml.variables["this_unit"] = nil -- clearing this_unit
 	wml.variables["this_unit"] = unit.__cfg -- cfg field needed
@@ -168,5 +168,4 @@ function wesnoth.wml_actions.find_path(cfg)
 
 	-- support for $this_unit
 	wml.variables["this_unit"] = nil -- clearing this_unit
-	utils.end_var_scope("this_unit", this_unit)
 end

data/lua/wml/harm_unit.lua

@@ -19,7 +19,7 @@ function wml_actions.harm_unit(cfg)
 		else return false end
 	end
 
-	local this_unit = utils.start_var_scope("this_unit")
+	local this_unit <close> = utils.scoepd_var("this_unit")
 
 	for index, unit_to_harm in ipairs(wesnoth.units.find_on_map(filter)) do
 		if unit_to_harm.valid then
@@ -204,5 +204,4 @@ function wml_actions.harm_unit(cfg)
 	end
 
 	wml.variables["this_unit"] = nil -- clearing this_unit
-	utils.end_var_scope("this_unit", this_unit)
 end

data/lua/wml/modify_unit.lua

@@ -184,12 +184,11 @@ local function simple_modify_unit(cfg)
 		end
 	end
 
-	local this_unit = utils.start_var_scope("this_unit")
+	local this_unit <close> = utils.scoped_var("this_unit")
 	for i, u in ipairs(wesnoth.units.find(filter)) do
 		wml.variables["this_unit"] = u.__cfg
 		handle_unit(u)
 	end
-	utils.end_var_scope("this_unit", this_unit)
 end
 
 function wml_actions.modify_unit(cfg)
@@ -289,11 +288,10 @@ function wml_actions.modify_unit(cfg)
 	wml_actions.store_unit { {"filter", filter}, variable = unit_variable }
 	local max_index = wml.variables[unit_variable .. ".length"] - 1
 
-	local this_unit = utils.start_var_scope("this_unit")
+	local this_unit <close> = utils.scoped_var("this_unit")
 	for current_unit = 0, max_index do
 		handle_unit(current_unit)
 	end
-	utils.end_var_scope("this_unit", this_unit)
 
 	wml.variables[unit_variable] = nil
 end

data/lua/wml/random_placement.lua

@@ -9,7 +9,7 @@ wesnoth.wml_actions.random_placement = function(cfg)
 	local num_items = cfg.num_items or wml.error("[random_placement] missing required 'num_items' attribute")
 	local variable = cfg.variable or wml.error("[random_placement] missing required 'variable' attribute")
 	local allow_less = cfg.allow_less == true
-	local variable_previous = utils.start_var_scope(variable)
+	local variable_previous <close> = utils.scoped_var(variable)
 	local math_abs = math.abs
 	local locs = wesnoth.get_locations(filter)
 	if type(num_items) == "string" then