Implemented binary resistances and some more (#18933)

- Fixed possible exploit with tamed pets having template immunities
- Implemented binary resistances
- Corrected resistances calculations
- Pets properly inherit players spell penetration
- Fixed doubled block calculation for damaging melee spells
- Auras removing snare effects will only remove the snaring component
- Shapeshifting will properly remove movement impairing auras only and not crowd control (dragon's breath)
- Immunities are properly checked versus all schools appearing in spell, unit is immune only if immune to all schools
- Spells with melee and magic school mask should compare armor reduction with resistances and select smaller reduction
- Demonic Circle: Teleport no longer removes root effects

(cherrypicked from 93746e8c4a79c8256cd4896533315683f143508c)

1 files changed, 7 insertions, 1 deletions

diff --git a/src/server/game/Spells/SpellInfo.cpp b/src/server/game/Spells/SpellInfo.cpp
index f643d7b3a2f..c416460080b 100644
--- a/src/server/game/Spells/SpellInfo.cpp
+++ b/src/server/game/Spells/SpellInfo.cpp
@@ -3441,7 +3441,13 @@ void SpellInfo::ApplyAllSpellImmunitiesTo(Unit* target, SpellEffectInfo const* e
                 target->ApplySpellImmune(Id, IMMUNITY_MECHANIC, i, apply);
 
         if (apply && HasAttribute(SPELL_ATTR1_DISPEL_AURAS_ON_IMMUNITY))
-            target->RemoveAurasWithMechanic(mechanicImmunity, AURA_REMOVE_BY_DEFAULT, Id);
+        {
+            // exception for purely snare mechanic (eg. hands of freedom)!
+            if (mechanicImmunity == (1 << MECHANIC_SNARE))
+                target->RemoveMovementImpairingAuras(false);
+            else
+                target->RemoveAurasWithMechanic(mechanicImmunity, AURA_REMOVE_BY_DEFAULT, Id);
+        }
     }
 
     if (uint32 dispelImmunity = immuneInfo->DispelImmune)