Core/Spell: check aura positivity per effect on spell hit

- Fixes applying DR to positive effects, and changing duration of whole aura

Closes #19447

(cherry picked from commit 232e631390a504b51d82a7b678b7cf26d49d182a)

1 files changed, 16 insertions, 7 deletions

diff --git a/src/server/game/Spells/Spell.cpp b/src/server/game/Spells/Spell.cpp
index a03788cdda5..4c2468cc3bc 100644
--- a/src/server/game/Spells/Spell.cpp
+++ b/src/server/game/Spells/Spell.cpp
@@ -2626,11 +2626,24 @@ SpellMissInfo Spell::DoSpellHitOnUnit(Unit* unit, uint32 effectMask)
                 }
 
                 // Now Reduce spell duration using data received at spell hit
+                // check whatever effects we're going to apply, diminishing returns only apply to negative aura effects
+                bool positive = true;
+                if (m_originalCaster == unit || !m_originalCaster->IsFriendlyTo(unit))
+                {
+                    for (uint8 i = 0; i < MAX_SPELL_EFFECTS; ++i)
+                    {
+                        if ((effectMask & (1 << i)) && !m_spellInfo->IsPositiveEffect(i))
+                        {
+                            positive = false;
+                            break;
+                        }
+                    }
+                }
+
                 int32 duration = m_spellAura->GetMaxDuration();
-                float diminishMod = unit->ApplyDiminishingToDuration(m_spellInfo, duration, m_originalCaster, diminishLevel);
 
                 // unit is immune to aura if it was diminished to 0 duration
-                if (diminishMod == 0.0f)
+                if (!positive && !unit->ApplyDiminishingToDuration(m_spellInfo, duration, m_originalCaster, diminishLevel))
                 {
                     m_spellAura->Remove();
                     bool found = false;
@@ -2642,11 +2655,7 @@ SpellMissInfo Spell::DoSpellHitOnUnit(Unit* unit, uint32 effectMask)
                 }
                 else
                 {
-                    ((UnitAura*)m_spellAura)->SetDiminishGroup(diminishGroup);
-
-                    bool positive = m_spellAura->GetSpellInfo()->IsPositive();
-                    if (AuraApplication* aurApp = m_spellAura->GetApplicationOfTarget(m_originalCaster->GetGUID()))
-                        positive = aurApp->IsPositive();
+                    static_cast<UnitAura*>(m_spellAura)->SetDiminishGroup(diminishGroup);
 
                     duration = m_originalCaster->ModSpellDuration(m_spellInfo, unit, duration, positive, effectMask);