Core/Auras: Fixed auras limited to a single target not being removed in all cases as expected

* Fixes possible assertion failure in Aura::UnregisterSingleTarget
Closes #15696
Ref #15668

Cherry picked (manually) from b808910a89822f741d35d4b90e6c4bcf101cd9ef

1 files changed, 13 insertions, 6 deletions

diff --git a/src/server/game/Entities/Unit/Unit.cpp b/src/server/game/Entities/Unit/Unit.cpp
index f085bab165a..9ced65b56c7 100644
--- a/src/server/game/Entities/Unit/Unit.cpp
+++ b/src/server/game/Entities/Unit/Unit.cpp
@@ -3908,20 +3908,27 @@ void Unit::RemoveAurasWithAttribute(uint32 flags)
 void Unit::RemoveNotOwnSingleTargetAuras(uint32 newPhase)
 {
     // single target auras from other casters
-    for (AuraApplicationMap::iterator iter = m_appliedAuras.begin(); iter != m_appliedAuras.end();)
+    // Iterate m_ownedAuras - aura is marked as single target in Unit::AddAura (and pushed to m_ownedAuras).
+    // m_appliedAuras will NOT contain the aura before first Unit::Update after adding it to m_ownedAuras.
+    // Quickly removing such an aura will lead to it not being unregistered from caster's single cast auras container
+    // leading to assertion failures if the aura was cast on a player that can
+    // (and is changing map at the point where this function is called).
+    // Such situation occurs when player is logging in inside an instance and fails the entry check for any reason.
+    // The aura that was loaded from db (indirectly, via linked casts) gets removed before it has a chance
+    // to register in m_appliedAuras
+    for (AuraMap::iterator iter = m_ownedAuras.begin(); iter != m_ownedAuras.end();)
     {
-        AuraApplication const* aurApp = iter->second;
-        Aura const* aura = aurApp->GetBase();
+        Aura const* aura = iter->second;
 
-        if (aura->GetCasterGUID() != GetGUID() && aura->GetSpellInfo()->IsSingleTarget())
+        if (aura->GetCasterGUID() != GetGUID() && aura->IsSingleTarget())
         {
             if (!newPhase)
-                RemoveAura(iter);
+                RemoveOwnedAura(iter);
             else
             {
                 Unit* caster = aura->GetCaster();
                 if (!caster || !caster->InSamePhase(newPhase))
-                    RemoveAura(iter);
+                    RemoveOwnedAura(iter);
                 else
                     ++iter;
             }