Fix the implementations of the deprecated get|set_terrain functions

data/lua/core.lua

@@ -819,11 +819,25 @@ if wesnoth.kernel_type() == "Game Lua Kernel" then
 	wesnoth.terrain_mask = wesnoth.deprecate_api('wesnoth.terrain_mask', 'wesnoth.map.get():terrain_mask', 1, nil, function(...)
 		get_map().terrain_mask(...)
 	end)
-	wesnoth.get_terrain = wesnoth.deprecate_api('wesnoth.get_terrain', 'wesnoth.map.get():get_terrain', 1, nil, function(...)
-		get_map().get_terrain(...)
+	wesnoth.get_terrain = wesnoth.deprecate_api('wesnoth.get_terrain', 'wesnoth.map.get():get_terrain', 1, nil, function(x, y)
+		local loc = wesnoth.read_location(x, y)
+		if loc == nil then error('get_terrain: expected location') end
+		return get_map()[loc]
 	end)
 	wesnoth.set_terrain = wesnoth.deprecate_api('wesnoth.set_terrain', 'wesnoth.map.get():set_terrain', 1, nil, function(...)
-		get_map().set_terrain(...)
+		local loc, n = wesnoth.read_location(...)
+		if n == 0 then error('set_terrain: expected location') end
+		local new_ter, mode, replace_if_failed = select(n + 1, ...)
+		if new_ter == '' or type(new_ter) ~= 'string' then error('set_terrain: expected terrain string') end
+		if replace_if_failed then
+			mode = mode or 'both'
+			new_ter = wesnoth.map.replace_if_failed(new_ter, mode, true)
+		elseif mode == 'both' or mode == 'base' or mode == 'overlay' then
+			new_ter = wesnoth.map['replace_' .. mode](new_ter)
+		else
+			error('set_terrain: invalid mode')
+		end
+		get_map()[loc] = new_ter
 	end)
 	wesnoth.get_map_size = wesnoth.deprecate_api('wesnoth.get_map_size', 'wesnoth.map.get().width,height,border_size', 1, nil, function()
 		local m = get_map()