Combat/Threat: Split ThreatManager::NotifyDisengaged off from ThreatManager::ClearAllThreat. NotifyDisengaged signifies intent to clear the engagement flag, and should only be called from AI.

Port From (https://github.com/TrinityCore/TrinityCore/commit/38d7c1530a65a7ff1bd10775c4a35269b2416538)

Source/Game/AI/CoreAI/CreatureAI.cs

@@ -224,18 +224,15 @@ namespace Game.AI
             me.RemoveAurasOnEvade();
 
             // sometimes bosses stuck in combat?
-            me.GetThreatManager().ClearAllThreat();
             me.CombatStop(true);
+            me.GetThreatManager().NotifyDisengaged();
             me.SetLootRecipient(null);
             me.ResetPlayerDamageReq();
             me.SetLastDamagedTime(0);
             me.SetCannotReachTarget(false);
             me.DoNotReacquireTarget();
 
-            if (me.IsInEvadeMode())
-                return false;
-
-            return true;
+            return !me.IsInEvadeMode();
         }
 
         public CypherStrings VisualizeBoundary(int duration, Unit owner = null, bool fill = false)

Source/Game/AI/CoreAI/GuardAI.cs

@@ -48,15 +48,15 @@ namespace Game.AI
             {
                 me.GetMotionMaster().MoveIdle();
                 me.CombatStop(true);
-                me.GetThreatManager().ClearAllThreat();
+                me.GetThreatManager().NotifyDisengaged();
                 return;
             }
 
             Log.outDebug(LogFilter.Unit, "Guard entry: {0} enters evade mode.", me.GetEntry());
 
             me.RemoveAllAuras();
-            me.GetThreatManager().ClearAllThreat();
             me.CombatStop(true);
+            me.GetThreatManager().NotifyDisengaged();
 
             me.GetMotionMaster().MoveTargetedHome();
         }

Source/Game/AI/ScriptedAI/ScriptedEscortAI.cs

@@ -134,8 +134,8 @@ namespace Game.AI
         public override void EnterEvadeMode(EvadeReason why = EvadeReason.Other)
         {
             me.RemoveAllAuras();
-            me.GetThreatManager().ClearAllThreat();
             me.CombatStop(true);
+            me.GetThreatManager().NotifyDisengaged();
             me.SetLootRecipient(null);
 
             if (HasEscortState(EscortState.Escorting))

Source/Game/AI/ScriptedAI/ScriptedFollowerAI.cs

@@ -126,8 +126,8 @@ namespace Game.AI
                 return;
 
             me.RemoveAllAuras();
-            me.GetThreatManager().ClearAllThreat();
             me.CombatStop(true);
+            me.GetThreatManager().NotifyDisengaged();
             me.SetLootRecipient(null);
             me.SetCannotReachTarget(false);
             me.DoNotReacquireTarget();

Source/Game/Combat/ThreatManager.cs

@@ -396,6 +396,14 @@ namespace Game.Combat
                     _myThreatListEntries.FirstOrDefault().Value.UnregisterAndFree();
                 while (!_myThreatListEntries.Empty());
             }
+        }
+
+        /// <summary>
+        /// THIS SHOULD ONLY BE CALLED FROM A CREATURE'S AI (typically in EnterEvadeMode)
+        /// notify the unit that the AI has disengaged
+        /// </summary>
+        public void NotifyDisengaged()
+        {
             // note: i don't really like having this here
             // (maybe engage flag should be in creature ai? it's inherently an AI property...)
             if (_owner.IsEngaged())

Source/Game/Entities/Unit/Unit.cs

@@ -1405,7 +1405,6 @@ namespace Game.Entities
             if (s != DeathState.Alive && s != DeathState.JustRespawned)
             {
                 CombatStop();
-                GetThreatManager().ClearAllThreat();
 
                 if (IsNonMeleeSpellCast(false))
                     InterruptNonMeleeSpells(false);

Source/Game/Maps/ObjectGridLoader.cs

@@ -216,7 +216,6 @@ namespace Game.Maps
                 if (creature.IsInCombat())
                 {
                     creature.CombatStop();
-                    creature.GetThreatManager().ClearAllThreat();
                     if (creature.IsAIEnabled())
                         creature.GetAI().EnterEvadeMode();
                 }

Source/Scripts/Pets/Priest.cs

@@ -44,8 +44,8 @@ namespace Scripts.Pets
                 if (!me.IsAlive())
                     return;
 
-                me.GetThreatManager().ClearAllThreat();
                 me.CombatStop(true);
+                me.GetThreatManager().NotifyDisengaged();
                 me.ResetPlayerDamageReq();
             }
         }