feat(Core/AI): allow instance creatures to teleport to unreachable targets (#26459)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/server/apps/worldserver/worldserver.conf.dist

@@ -3184,6 +3184,16 @@ WaypointMovementStopTimeForPlayer = 120
 
 NpcRegenHPIfTargetIsUnreachable = 1
 
+#    Creature.Instance.TeleportToUnreachableTarget
+#        Description: In dungeons and raids, non-boss creatures that cannot path to their
+#                     target teleport to it instead of evading or regenerating in place
+#                     (retail-like behaviour). Bosses and player-controlled creatures are
+#                     not affected.
+#        Default:     0 - (Disabled)
+#                     1 - (Enabled)
+
+Creature.Instance.TeleportToUnreachableTarget = 0
+
 #    Creatures.CustomIDs
 #        Description: The list of custom creatures with gossip dialogues hardcoded in core,
 #                     divided by "," without spaces.

src/server/game/AI/CoreAI/UnitAI.cpp

@@ -24,6 +24,7 @@
 #include "SpellAuraEffects.h"
 #include "SpellInfo.h"
 #include "SpellMgr.h"
+#include "World.h"
 
 void UnitAI::AttackStart(Unit* victim)
 {
@@ -414,6 +415,26 @@ void UnitAI::EvadeTimerExpired()
         }
     }
 
+    // Retail-like: instance trash teleports to its unreachable target instead of evading
+    if (sWorld->getBoolConfig(CONFIG_CREATURE_INSTANCE_TELEPORT_TO_UNREACHABLE_TARGET)
+        && creature->GetMap()->IsDungeon()
+        && !creature->IsDungeonBoss() && !creature->isWorldBoss()
+        && !creature->IsControlledByPlayer())
+    {
+        if (ObjectGuid targetGuid = creature->GetCannotReachTarget())
+        {
+            if (Unit* target = ObjectAccessor::GetUnit(*creature, targetGuid))
+            {
+                if (target->IsAlive() && creature->IsEngagedBy(target))
+                {
+                    creature->NearTeleportTo(target->GetPositionX(), target->GetPositionY(), target->GetPositionZ(), target->GetOrientation());
+                    creature->SetCannotReachTarget();
+                    return;
+                }
+            }
+        }
+    }
+
     if (creature->GetMap()->IsRaid())
     {
         creature->GetCombatManager().ContinueEvadeRegen();

src/server/game/World/WorldConfig.cpp

@@ -477,6 +477,7 @@ void WorldConfig::BuildConfigCache()
 
     SetConfigValue<bool>(CONFIG_OFFHAND_CHECK_AT_SPELL_UNLEARN, "OffhandCheckAtSpellUnlearn", true);
     SetConfigValue<bool>(CONFIG_CREATURE_REPOSITION_AGAINST_NPCS, "Creature.RepositionAgainstNpcs", true);
+    SetConfigValue<bool>(CONFIG_CREATURE_INSTANCE_TELEPORT_TO_UNREACHABLE_TARGET, "Creature.Instance.TeleportToUnreachableTarget", false);
     SetConfigValue<uint32>(CONFIG_CREATURE_STOP_FOR_PLAYER, "Creature.MovingStopTimeForPlayer", 180000);
 
     SetConfigValue<uint32>(CONFIG_WATER_BREATH_TIMER, "WaterBreath.Timer", 180000, ConfigValueCache::Reloadable::Yes, [](uint32 const& value) { return value > 0; }, "> 0");

src/server/game/World/WorldConfig.h

@@ -75,6 +75,7 @@ enum ServerConfigs
     CONFIG_ARENA_QUEUE_ANNOUNCER_PLAYERONLY,
     CONFIG_OFFHAND_CHECK_AT_SPELL_UNLEARN,
     CONFIG_CREATURE_REPOSITION_AGAINST_NPCS,
+    CONFIG_CREATURE_INSTANCE_TELEPORT_TO_UNREACHABLE_TARGET,
     CONFIG_VMAP_INDOOR_CHECK,
     CONFIG_VMAP_ENABLE_LOS,
     CONFIG_VMAP_ENABLE_HEIGHT,