Core/Units: add new functionality for units to block or enable combat interactions (#25168)

* Core/Units: add new functionality for units to block or enable combat entirely via helper to reflect what CREATURE_DIFFICULTYFLAGS_IGNORE_COMBAT and client AI functions imply

* yeah...

* Nuke Creature::IsCombatDisallowed helper as its unused by now

* no combat extra flag may now be changed on transforms if the transformed entry does not have the flag

(cherry picked from commit 764f22fc9157ad184baa38995ee4e2d821299935)

5 files changed, 13 insertions, 7 deletions

diff --git a/src/server/game/Combat/CombatManager.cpp b/src/server/game/Combat/CombatManager.cpp
index edf47fdca87..d0401ded76c 100644
--- a/src/server/game/Combat/CombatManager.cpp
+++ b/src/server/game/Combat/CombatManager.cpp
@@ -43,12 +43,9 @@
         return false;
     if (a->HasUnitState(UNIT_STATE_IN_FLIGHT) || b->HasUnitState(UNIT_STATE_IN_FLIGHT))
         return false;
-    if (Creature const* aCreature = a->ToCreature())
-        if (aCreature->IsCombatDisallowed())
-            return false;
-    if (Creature const* bCreature = b->ToCreature())
-        if (bCreature->IsCombatDisallowed())
-            return false;
+    // ... both units must not be ignoring combat
+    if (a->IsIgnoringCombat() || b->IsIgnoringCombat())
+        return false;
     if (a->IsFriendlyTo(b) || b->IsFriendlyTo(a))
         return false;
     Player const* playerA = a->GetCharmerOrOwnerPlayerOrPlayerItself();
diff --git a/src/server/game/Entities/Creature/Creature.cpp b/src/server/game/Entities/Creature/Creature.cpp
index c7d92bc46a2..4d17c7a6c0b 100644
--- a/src/server/game/Entities/Creature/Creature.cpp
+++ b/src/server/game/Entities/Creature/Creature.cpp
@@ -680,6 +680,8 @@ bool Creature::UpdateEntry(uint32 entry, CreatureData const* data /*= nullptr*/,
         ApplySpellImmune(0, IMMUNITY_EFFECT, SPELL_EFFECT_ATTACK_ME, true);
     }
 
+    SetIgnoringCombat((cInfo->flags_extra & CREATURE_FLAG_EXTRA_NO_COMBAT) != 0);
+
     LoadTemplateRoot();
     InitializeMovementFlags();
 
diff --git a/src/server/game/Entities/Creature/Creature.h b/src/server/game/Entities/Creature/Creature.h
index 8b0dc29f542..1a67853ebf1 100644
--- a/src/server/game/Entities/Creature/Creature.h
+++ b/src/server/game/Entities/Creature/Creature.h
@@ -105,7 +105,6 @@ class TC_GAME_API Creature : public Unit, public GridObject<Creature>, public Ma
         bool IsCivilian() const { return (GetCreatureTemplate()->flags_extra & CREATURE_FLAG_EXTRA_CIVILIAN) != 0; }
         bool IsTrigger() const { return (GetCreatureTemplate()->flags_extra & CREATURE_FLAG_EXTRA_TRIGGER) != 0; }
         bool IsGuard() const { return (GetCreatureTemplate()->flags_extra & CREATURE_FLAG_EXTRA_GUARD) != 0; }
-        bool IsCombatDisallowed() const { return (GetCreatureTemplate()->flags_extra & CREATURE_FLAG_EXTRA_NO_COMBAT) != 0; }
 
         void InitializeMovementFlags();
         void UpdateMovementFlags();
diff --git a/src/server/game/Entities/Unit/Unit.cpp b/src/server/game/Entities/Unit/Unit.cpp
index 49b3b19be9b..057fd26a731 100644
--- a/src/server/game/Entities/Unit/Unit.cpp
+++ b/src/server/game/Entities/Unit/Unit.cpp
@@ -400,6 +400,7 @@ Unit::Unit(bool isWorldObject) :
     _oldFactionId = 0;
     _isWalkingBeforeCharm = false;
     _instantCast = false;
+    _isIgnoringCombat = false;
 }
 
 ////////////////////////////////////////////////////////////
diff --git a/src/server/game/Entities/Unit/Unit.h b/src/server/game/Entities/Unit/Unit.h
index 520b6fb1a30..6e255d8e0f6 100644
--- a/src/server/game/Entities/Unit/Unit.h
+++ b/src/server/game/Entities/Unit/Unit.h
@@ -1849,6 +1849,11 @@ class TC_GAME_API Unit : public WorldObject
         uint16 GetVirtualItemAppearanceMod(uint32 slot) const;
         void SetVirtualItem(uint32 slot, uint32 itemId, uint16 appearanceModId = 0, uint16 itemVisual = 0);
 
+        // returns if the unit is ignoring any combat interaction
+        bool IsIgnoringCombat() const { return _isIgnoringCombat; }
+        // enables/disables combat interaction of this unit.
+        void SetIgnoringCombat(bool apply) { _isIgnoringCombat = apply; }
+
         std::string GetDebugInfo() const override;
 
         UF::UpdateField<UF::UnitData, 0, TYPEID_UNIT> m_unitData;
@@ -2017,6 +2022,8 @@ class TC_GAME_API Unit : public WorldObject
 
         std::unique_ptr<MovementForces> _movementForces;
         PositionUpdateInfo _positionUpdateInfo;
+
+        bool _isIgnoringCombat;
 };
 
 namespace Trinity