use lua filter in {ABILITY_TELEPORT}

this way it no longer uses variable substitution

Fixes #1281

data/core/_main.cfg

@@ -8,6 +8,7 @@
 wesnoth.dofile 'lua/backwards-compatibility.lua'
 wesnoth.dofile 'lua/wml-tags.lua'
 wesnoth.dofile 'lua/feeding.lua'
+wesnoth.dofile 'lua/teleport_filter.lua'
 >>
 [/lua]
 

data/core/macros/abilities.cfg

@@ -201,25 +201,15 @@ Any units adjacent to this unit will fight as if it were dusk when it is night,
         description= _ "This unit may teleport between any two empty villages owned by its side using one of its moves."
         [tunnel]
             id=village_teleport
+
             [source]
                 terrain=*^V*
-                owner_side=$teleport_unit.side
-                [not]
-                    [filter]
-                        [not]
-                            id=$teleport_unit.id
-                        [/not]
-                    [/filter]
-                [/not]
+                lua_function="teleport_source_filter"
             [/source]
 
             [target]
                 terrain=*^V*
-                owner_side=$teleport_unit.side
-                [not]
-                    [filter]
-                    [/filter]
-                [/not]
+                lua_function="teleport_target_filter"
             [/target]
 
             [filter]

data/lua/teleport_filter.lua

@@ -0,0 +1,15 @@
+function teleport_source_filter(x, y)
+	if wesnoth.get_village_owner(x, y) ~= wesnoth.get_variable("teleport_unit.side") then
+		return false
+	end
+	local blocking_unit = wesnoth.get_unit(x, y)
+	return (not blocking_unit) or blocking_unit.id == wesnoth.get_variable("teleport_unit.id")
+end
+
+function teleport_target_filter(x, y)
+	if wesnoth.get_village_owner(x, y) ~= wesnoth.get_variable("teleport_unit.side") then
+		return false
+	end
+	local blocking_unit = wesnoth.get_unit(x, y)
+	return not blocking_unit
+end