Core/Spells: add correct checking for dispeling errors. Fixes spammable cleanse.

src/server/game/Entities/Unit/Unit.cpp

@@ -4113,6 +4113,45 @@ Aura* Unit::GetAuraOfRankedSpell(uint32 spellId, uint64 casterGUID, uint64 itemC
     return aurApp ? aurApp->GetBase() : NULL;
 }
 
+void Unit::GetDispellableAuraList(Unit* caster, uint32 dispelMask, DispelChargesList& dispelList)
+{
+    // we should not be able to dispel diseases if the target is affected by unholy blight
+    if (dispelMask & (1 << DISPEL_DISEASE) && HasAura(50536))
+        dispelMask &= ~(1 << DISPEL_DISEASE);
+
+    AuraMap const& auras = GetOwnedAuras();
+    for (AuraMap::const_iterator itr = auras.begin(); itr != auras.end(); ++itr)
+    {
+        Aura* aura = itr->second;
+        AuraApplication * aurApp = aura->GetApplicationOfTarget(GetGUID());
+        if (!aurApp)
+            continue;
+
+        // don't try to remove passive auras
+        if (aura->IsPassive())
+            continue;
+
+        if (aura->GetSpellInfo()->GetDispelMask() & dispelMask)
+        {
+            if (aura->GetSpellInfo()->Dispel == DISPEL_MAGIC)
+            {
+                // do not remove positive auras if friendly target
+                //               negative auras if non-friendly target
+                if (aurApp->IsPositive() == IsFriendlyTo(caster))
+                    continue;
+            }
+
+            // The charges / stack amounts don't count towards the total number of auras that can be dispelled.
+            // Ie: A dispel on a target with 5 stacks of Winters Chill and a Polymorph has 1 / (1 + 1) -> 50% chance to dispell
+            // Polymorph instead of 1 / (5 + 1) -> 16%.
+            bool dispel_charges = aura->GetSpellInfo()->AttributesEx7 & SPELL_ATTR7_DISPEL_CHARGES;
+            uint8 charges = dispel_charges ? aura->GetCharges() : aura->GetStackAmount();
+            if (charges > 0)
+                dispelList.push_back(std::make_pair(aura, charges));
+        }
+    }
+}
+
 bool Unit::HasAuraEffect(uint32 spellId, uint8 effIndex, uint64 caster) const
 {
     for (AuraApplicationMap::const_iterator itr = m_appliedAuras.lower_bound(spellId); itr != m_appliedAuras.upper_bound(spellId); ++itr)