From eaa635ab3284652e652f299bf90c679c6a76ecde Mon Sep 17 00:00:00 2001
From: Ovahlord <dreadkiller@gmx.de>
Date: Fri, 31 Jan 2020 06:34:18 +0100
Subject: [PATCH] Core/Movement: backported cleanup for determining follow
 movement on appearing instead of calling evade modes right away

---
 src/server/game/AI/CreatureAI.cpp       | 50 +++++++++++++++++++++++++
 src/server/game/AI/CreatureAI.h         |  2 +-
 src/server/game/Spells/SpellEffects.cpp |  4 --
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/src/server/game/AI/CreatureAI.cpp b/src/server/game/AI/CreatureAI.cpp
index 13f185fc6ed..c27b3af782b 100644
--- a/src/server/game/AI/CreatureAI.cpp
+++ b/src/server/game/AI/CreatureAI.cpp
@@ -186,6 +186,56 @@ void CreatureAI::TriggerAlert(Unit const* who) const
     me->SetFacingTo(me->GetAngle(who));
 }
 
+// adapted from logic in Spell:EFfectSummonType before commit 8499434
+static bool ShouldFollowOnSpawn(SummonPropertiesEntry const* properties)
+{
+    // Summons without SummonProperties are generally scripted summons that don't belong to any owner
+    if (!properties)
+        return false;
+
+    switch (properties->Control)
+    {
+        case SUMMON_CATEGORY_PET:
+            return true;
+        case SUMMON_CATEGORY_WILD:
+        case SUMMON_CATEGORY_ALLY:
+        case SUMMON_CATEGORY_UNK:
+            if (properties->Flags & 512)
+                return true;
+            switch (properties->Title)
+            {
+                case SUMMON_TYPE_PET:
+                case SUMMON_TYPE_GUARDIAN:
+                case SUMMON_TYPE_GUARDIAN2:
+                case SUMMON_TYPE_MINION:
+                case SUMMON_TYPE_MINIPET:
+                    return true;
+                default:
+                    return false;
+            }
+        default:
+            return false;
+    }
+}
+void CreatureAI::JustAppeared()
+{
+    if (!me->IsInCombat())
+    {
+        if (TempSummon* summon = me->ToTempSummon())
+        {
+            // Only apply this to specific types of summons
+            if (!summon->GetVehicle() && ShouldFollowOnSpawn(summon->m_Properties))
+            {
+                if (Unit* owner = summon->GetCharmerOrOwner())
+                {
+                    summon->GetMotionMaster()->Clear();
+                    summon->GetMotionMaster()->MoveFollow(owner, PET_FOLLOW_DIST, summon->GetFollowAngle());
+                }
+            }
+        }
+    }
+}
+
 void CreatureAI::EnterEvadeMode(EvadeReason why)
 {
     if (!_EnterEvadeMode(why))
diff --git a/src/server/game/AI/CreatureAI.h b/src/server/game/AI/CreatureAI.h
index 581e409d21b..f950b236de2 100644
--- a/src/server/game/AI/CreatureAI.h
+++ b/src/server/game/AI/CreatureAI.h
@@ -143,7 +143,7 @@ class TC_GAME_API CreatureAI : public UnitAI
         virtual bool IsEscorted() const { return false; }
 
         // Called when creature appears in the world (spawn, respawn, grid load etc...)
-        virtual void JustAppeared() { }
+        virtual void JustAppeared();
 
         // Called at waypoint reached or point movement finished
         virtual void MovementInform(uint32 /*type*/, uint32 /*id*/) { }
diff --git a/src/server/game/Spells/SpellEffects.cpp b/src/server/game/Spells/SpellEffects.cpp
index 67ff0db9921..b59ccb96de2 100644
--- a/src/server/game/Spells/SpellEffects.cpp
+++ b/src/server/game/Spells/SpellEffects.cpp
@@ -1929,8 +1929,6 @@ void Spell::EffectSummonType(SpellEffIndex effIndex)
                     summon->SetUInt32Value(UNIT_NPC_FLAGS, summon->GetCreatureTemplate()->npcflag);
 
                     summon->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_IMMUNE_TO_PC | UNIT_FLAG_IMMUNE_TO_NPC);
-
-                    summon->AI()->EnterEvadeMode();
                     break;
                 }
                 default:
@@ -5383,8 +5381,6 @@ void Spell::SummonGuardian(uint32 i, uint32 entry, SummonPropertiesEntry const*
                 summon->SetDisplayId(1126); // modelid1
         }
 
-        summon->AI()->EnterEvadeMode();
-
         ExecuteLogEffectSummonObject(i, summon);
     }
 }