Core/Auras: Recheck aura presence on target after calling linked events in aura effect handlers. Prevents undefined behavious when aura effect remove handler is called before apply handler is finished.

src/server/game/Spells/Auras/SpellAuraEffects.cpp

@@ -988,8 +988,11 @@ void AuraEffect::HandleEffect(AuraApplication const * aurApp, uint8 mode, bool a
     else
         prevented = GetBase()->CallScriptEffectRemoveHandlers(const_cast<AuraEffect const *>(this), aurApp, (AuraEffectHandleModes)mode);
 
-    if (!prevented)
+    // check if script events have removed the aura or if default effect prevention was requested
-        (*this.*AuraEffectHandler [GetAuraType()])(aurApp, mode, apply);
+    if ((apply && aurApp->GetRemoveMode()) || prevented)
+        return;
+
+    (*this.*AuraEffectHandler [GetAuraType()])(aurApp, mode, apply);
 }
 
 void AuraEffect::HandleEffect(Unit * target, uint8 mode, bool apply)
@@ -2828,6 +2831,10 @@ void AuraEffect::HandleModStealth(AuraApplication const * aurApp, uint8 mode, bo
             target->RemoveAurasWithInterruptFlags(AURA_INTERRUPT_FLAG_IMMUNE_OR_LOST_SELECTION);
         }
 
+        // stop handling the effect if it was removed by linked event
+        if (aurApp->GetRemoveMode())
+            return;
+
         target->m_stealth.AddFlag( type);
         target->m_stealth.AddValue(type, GetAmount());
 
@@ -2953,6 +2960,10 @@ void AuraEffect::HandlePhase(AuraApplication const * aurApp, uint8 mode, bool ap
             if (Battleground *bg = player->GetBattleground())
                 bg->EventPlayerDroppedFlag(player);
 
+        // stop handling the effect if it was removed by linked event
+        if (aurApp->GetRemoveMode())
+            return;
+
         // GM-mode have mask 0xFFFFFFFF
         if (player->isGameMaster())
             newPhase = 0xFFFFFFFF;
@@ -3071,6 +3082,10 @@ void AuraEffect::HandleAuraModShapeshift(AuraApplication const * aurApp, uint8 m
         // remove other shapeshift before applying a new one
         target->RemoveAurasByType(SPELL_AURA_MOD_SHAPESHIFT, 0, GetBase());
 
+        // stop handling the effect if it was removed by linked event
+        if (aurApp->GetRemoveMode())
+            return;
+
         if (modelid > 0)
             target->SetDisplayId(modelid);
 
@@ -3117,6 +3132,9 @@ void AuraEffect::HandleAuraModShapeshift(AuraApplication const * aurApp, uint8 m
                     break;
             }
         }
+        // stop handling the effect if it was removed by linked event
+        if (aurApp->GetRemoveMode())
+            return;
 
         target->SetShapeshiftForm(form);
     }
@@ -3221,6 +3239,10 @@ void AuraEffect::HandleAuraModShapeshift(AuraApplication const * aurApp, uint8 m
         }
     }
 
+    // stop handling the effect if it was removed by linked event
+    if (apply && aurApp->GetRemoveMode())
+        return;
+
     if (target->GetTypeId() == TYPEID_PLAYER)
     {
         SpellShapeshiftEntry const *shapeInfo = sSpellShapeshiftStore.LookupEntry(form);
@@ -3485,14 +3507,6 @@ void AuraEffect::HandleFeignDeath(AuraApplication const * aurApp, uint8 mode, bo
                 }
             }
         }
-                                                            // blizz like 2.0.x
-        target->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_UNK_29);
-                                                            // blizz like 2.0.x
-        target->SetFlag(UNIT_FIELD_FLAGS_2, UNIT_FLAG2_FEIGN_DEATH);
-                                                            // blizz like 2.0.x
-        target->SetFlag(UNIT_DYNAMIC_FLAGS, UNIT_DYNFLAG_DEAD);
-
-        target->AddUnitState(UNIT_STAT_DIED);
         target->CombatStop();
         target->RemoveAurasWithInterruptFlags(AURA_INTERRUPT_FLAG_IMMUNE_OR_LOST_SELECTION);
 
@@ -3501,6 +3515,18 @@ void AuraEffect::HandleFeignDeath(AuraApplication const * aurApp, uint8 mode, bo
             target->FinishSpell(CURRENT_GENERIC_SPELL, false);
         target->InterruptNonMeleeSpells(true);
         target->getHostileRefManager().deleteReferences();
+
+        // stop handling the effect if it was removed by linked event
+        if (aurApp->GetRemoveMode())
+            return;
+                                                            // blizz like 2.0.x
+        target->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_UNK_29);
+                                                            // blizz like 2.0.x
+        target->SetFlag(UNIT_FIELD_FLAGS_2, UNIT_FLAG2_FEIGN_DEATH);
+                                                            // blizz like 2.0.x
+        target->SetFlag(UNIT_DYNAMIC_FLAGS, UNIT_DYNFLAG_DEAD);
+
+        target->AddUnitState(UNIT_STAT_DIED);
     }
     else
     {
@@ -3535,6 +3561,9 @@ void AuraEffect::HandleModUnattackable(AuraApplication const * aurApp, uint8 mod
             target->CombatStop();
             target->RemoveAurasWithInterruptFlags(AURA_INTERRUPT_FLAG_IMMUNE_OR_LOST_SELECTION);
         }
+        // stop handling the effect if it was removed by linked event
+        if (aurApp->GetRemoveMode())
+            return;
     }
     // do not remove unit flag if there are more than this auraEffect of that kind on unit on unit
     else if (target->HasAuraType(SPELL_AURA_MOD_UNATTACKABLE))
@@ -3600,8 +3629,6 @@ void AuraEffect::HandleAuraModDisarm(AuraApplication const * aurApp, uint8 mode,
         }
     }
 
-
-
     if (target->GetTypeId() == TYPEID_UNIT && target->ToCreature()->GetCurrentEquipmentId())
         target->UpdateDamagePhysical(attType);
 }
@@ -4476,6 +4503,9 @@ void AuraEffect::HandleAuraModEffectImmunity(AuraApplication const * aurApp, uin
                 sOutdoorPvPMgr->HandleDropFlag((Player*)target,GetSpellProto()->Id);
         }
     }
+    // stop handling the effect if it was removed by linked event
+    if (apply && aurApp->GetRemoveMode())
+        return;
 
     target->ApplySpellImmune(GetId(),IMMUNITY_EFFECT,GetMiscValue(),apply);
 }
@@ -4491,6 +4521,9 @@ void AuraEffect::HandleAuraModStateImmunity(AuraApplication const * aurApp, uint
     {
         target->RemoveAurasByType(AuraType(GetMiscValue()), NULL , GetBase());
     }
+    // stop handling the effect if it was removed by linked event
+    if (apply && aurApp->GetRemoveMode())
+        return;
 
     target->ApplySpellImmune(GetId(), IMMUNITY_STATE, GetMiscValue(), apply);
 }
@@ -4505,6 +4538,10 @@ void AuraEffect::HandleAuraModSchoolImmunity(AuraApplication const * aurApp, uin
     if ((apply) && GetMiscValue() == SPELL_SCHOOL_MASK_NORMAL)
         target->RemoveAurasWithInterruptFlags(AURA_INTERRUPT_FLAG_IMMUNE_OR_LOST_SELECTION);
 
+    // stop handling the effect if it was removed by linked event
+    if (apply && aurApp->GetRemoveMode())
+        return;
+
     target->ApplySpellImmune(GetId(),IMMUNITY_SCHOOL,GetMiscValue(),(apply));
 
     // remove all flag auras (they are positive, but they must be removed when you are immune)
@@ -4533,6 +4570,11 @@ void AuraEffect::HandleAuraModSchoolImmunity(AuraApplication const * aurApp, uin
                 ++iter;
         }
     }
+
+    // stop handling the effect if it was removed by linked event
+    if (apply && aurApp->GetRemoveMode())
+        return;
+
     if (GetSpellProto()->Mechanic == MECHANIC_BANISH)
     {
         if (apply)
@@ -6200,6 +6242,10 @@ void AuraEffect::HandleAuraDummy(AuraApplication const * aurApp, uint8 mode, boo
             break;
     }
 
+    // stop handling the effect if it was removed by linked event
+    if (apply && aurApp->GetRemoveMode())
+        return;
+
     if (mode & AURA_EFFECT_HANDLE_REAL)
     {
         // pet auras
@@ -6405,7 +6451,6 @@ void AuraEffect::HandleAuraConvertRune(AuraApplication const * aurApp, uint8 mod
                 continue;
             if (!plr->GetRuneCooldown(i))
             {
-                // ConvertRune(i,
                 plr->AddRuneByAuraEffect(i, RuneType(GetMiscValueB()), this);
                 --runes;
             }