Lua AIs: don't initiate variables as empty tables

... if they might not be needed.

(cherry-picked from commit a23f06dc20)

data/ai/lua/generic_rush_engine.lua

@@ -298,7 +298,7 @@ return {
             local enemy_attack_map = BC.get_attack_map(enemies).units
 
             -- Now we go through the villages and units
-            local max_rating, best_village, best_unit = - math.huge, {}, {}
+            local max_rating, best_village, best_unit = - math.huge
             local village_ratings = {}
             for j,v in ipairs(villages) do
                 -- First collect all information that only depends on the village
@@ -370,7 +370,7 @@ return {
                 end
             end
 
-            if (max_rating > - math.huge) then
+            if best_village then
                 self.data.unit, self.data.village = best_unit, best_village
                 if (max_rating >= 1000) then
                     if AH.print_eval() then AH.done_eval_messages(start_time, ca_name) end
@@ -423,7 +423,7 @@ return {
             end
 
             -- Go through all possible attacks with poisoners
-            local max_rating, best_attack = - math.huge, {}
+            local max_rating, best_attack = - math.huge
             for i,a in ipairs(attacks) do
                 local attacker = wesnoth.get_unit(a.src.x, a.src.y)
                 local defender = wesnoth.get_unit(a.target.x, a.target.y)
@@ -465,7 +465,7 @@ return {
                 end
             end
 
-            if (max_rating > - math.huge) then
+            if best_attack then
                 self.data.attack = best_attack
                 if AH.print_eval() then AH.done_eval_messages(start_time, ca_name) end
                 return 190000

data/ai/micro_ais/cas/ca_forest_animals_tusklet_move.lua

@@ -33,7 +33,7 @@ function ca_forest_animals_tusklet_move:execution(cfg)
     local tusklet = get_tusklets(cfg)[1]
     local tuskers = get_tuskers(cfg)
 
-    local goto_tusker, min_dist = {}, math.huge
+    local min_dist, goto_tusker = math.huge
     for _,tusker in ipairs(tuskers) do
         local dist = M.distance_between(tusker.x, tusker.y, tusklet.x, tusklet.y)
         if (dist < min_dist) then

data/campaigns/Eastern_Invasion/ai/ca_ogres_flee.lua

@@ -29,7 +29,7 @@ function ca_ogres_flee:execution()
     local enemies = wesnoth.get_units {  { "filter_side", { {"enemy_of", {side = wesnoth.current.side} } } } }
     local enemy_attack_map = BC.get_attack_map(enemies)
 
-    local max_rating, best_hex, best_unit = - math.huge, {}
+    local max_rating, best_hex, best_unit = - math.huge
     for i,u in ipairs(units) do
         local reach = wesnoth.find_reach(u)
 

data/campaigns/Son_Of_The_Black_Eye/ai/ca_transport_S6.lua

@@ -104,7 +104,7 @@ function ca_transport:execution()
         end
     end
 
-    if (max_rating > - math.huge) then
+    if best_unit then
         ai.move_full(best_unit, best_hex[1], best_hex[2])
 
         -- Also unload units
@@ -128,12 +128,12 @@ function ca_transport:execution()
         }
     )
 
-    local max_rating, best_unit, best_hex = - math.huge, {}, {}
+    local max_rating, best_unit, best_hex = - math.huge
     for i,u in ipairs(transports) do
         local dst = { u.variables.destination_x, u.variables.destination_y }
         local reach = wesnoth.find_reach(u)
 
-        local max_rating_unit, best_hex_unit = - math.huge, {}
+        local max_rating_unit, best_hex_unit = - math.huge
         for i,r in ipairs(reach) do
             if deep_water_map:get(r[1], r[2]) and (not blocked_hex_map:get(r[1], r[2])) then
                 local rating = -M.distance_between(r[1], r[2], dst[1], dst[2])
@@ -149,7 +149,7 @@ function ca_transport:execution()
 
         -- We give a penalty to hexes occupied by another transport that can still move away.
         -- All ratings need to be set to the same value for this to work.
-        if (max_rating_unit > - math.huge) then
+        if best_hex_unit then
             max_rating_unit = 0
             if transport_map:get(best_hex_unit[1], best_hex_unit[2]) then
                 max_rating_unit = -1
@@ -163,7 +163,7 @@ function ca_transport:execution()
         end
     end
 
-    if best_unit.id then
+    if best_unit then
         ai.move_full(best_unit, best_hex[1], best_hex[2])
     else  -- still need to make sure gamestate gets changed
         ai.stopunit_moves(transports[1])

data/campaigns/The_Rise_Of_Wesnoth/ai/ca_aggressive_attack_no_suicide.lua

@@ -15,7 +15,7 @@ function ca_aggressive_attack_no_suicide:evaluation(cfg, data)
     if (not attacks[1]) then return 0 end
 
     -- Now find the best of the possible attacks
-    local max_rating, best_attack = - math.huge, {}
+    local max_rating, best_attack = - math.huge
     for i, att in ipairs(attacks) do
         local attacker = wesnoth.get_unit(att.src.x, att.src.y)
         local defender = wesnoth.get_unit(att.target.x, att.target.y)
@@ -44,7 +44,7 @@ function ca_aggressive_attack_no_suicide:evaluation(cfg, data)
         end
     end
 
-    if (max_rating > - math.huge) then
+    if best_attack then
         data.attack = best_attack
         return 100000
     end