Core/Movement: Add some extra assertions to MotionMaster to catch issues like #22444 earlier in the future.

(cherry picked from commit ead439fbd6620ab53530c3d1d28b4755280a1059)

4 files changed, 7 insertions, 5 deletions

diff --git a/src/server/game/Handlers/TaxiHandler.cpp b/src/server/game/Handlers/TaxiHandler.cpp
index da4800ca319..ca4efad8e78 100644
--- a/src/server/game/Handlers/TaxiHandler.cpp
+++ b/src/server/game/Handlers/TaxiHandler.cpp
@@ -130,8 +130,6 @@ void WorldSession::SendDoFlight(uint32 mountDisplayId, uint32 path, uint32 pathN
     if (GetPlayer()->HasUnitState(UNIT_STATE_DIED))
         GetPlayer()->RemoveAurasByType(SPELL_AURA_FEIGN_DEATH);
 
-    GetPlayer()->GetMotionMaster()->Remove(FLIGHT_MOTION_TYPE);
-
     if (mountDisplayId)
         GetPlayer()->Mount(mountDisplayId);
 
diff --git a/src/server/game/Movement/MotionMaster.cpp b/src/server/game/Movement/MotionMaster.cpp
index b7c76bd4431..a3c8b04f9a7 100644
--- a/src/server/game/Movement/MotionMaster.cpp
+++ b/src/server/game/Movement/MotionMaster.cpp
@@ -974,7 +974,8 @@ void MotionMaster::MoveTaxiFlight(uint32 path, uint32 pathnode)
             TC_LOG_DEBUG("movement.motionmaster", "MotionMaster::MoveTaxiFlight: '%s', taxi to path Id: %u (node %u)", _owner->GetGUID().ToString().c_str(), path, pathnode);
 
             // Only one FLIGHT_MOTION_TYPE is allowed
-            Remove(FLIGHT_MOTION_TYPE);
+            bool hasExisting = HasMovementGenerator([](MovementGenerator const* gen) { return gen->GetMovementGeneratorType() == FLIGHT_MOTION_TYPE; });
+            ASSERT(!hasExisting, "Duplicate flight path movement generator");
 
             FlightPathMovementGenerator* movement = new FlightPathMovementGenerator();
             movement->LoadPath(_owner->ToPlayer(), pathnode);
diff --git a/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.cpp b/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.cpp
index 3aa391e2c1c..586d054d024 100644
--- a/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.cpp
+++ b/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.cpp
@@ -256,7 +256,10 @@ void FlightPathMovementGenerator::InitEndGridInfo()
     uint32 nodeCount = _path.size(); //! Number of nodes in path.
     ASSERT(nodeCount, "FlightPathMovementGenerator::InitEndGridInfo() called with empty _path");
     _endMapId = _path[nodeCount - 1]->ContinentID; //! MapId of last node
-    _preloadTargetNode = nodeCount - 3;
+    if (nodeCount < 3)
+        _preloadTargetNode = 0;
+    else
+        _preloadTargetNode = nodeCount - 3;
     _endGridX = _path[nodeCount - 1]->Loc.X;
     _endGridY = _path[nodeCount - 1]->Loc.Y;
 }
diff --git a/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.h b/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.h
index 6dc32e9ec84..5ae722964b6 100644
--- a/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.h
+++ b/src/server/game/Movement/MovementGenerators/FlightPathMovementGenerator.h
@@ -47,7 +47,7 @@ class FlightPathMovementGenerator : public MovementGeneratorMedium<Player, Fligh
         uint32 GetPathAtMapEnd() const;
         bool HasArrived() const { return _currentNode >= _path.size(); }
 
-        void LoadPath(Player* owner, uint32 startNode = 0);
+        void LoadPath(Player* owner, uint32 startNode = 0); // called from MotionMaster
         void SetCurrentNodeAfterTeleport();
         void SkipCurrentNode() { ++_currentNode; }
         void DoEventIfAny(Player* owner, TaxiPathNodeEntry const* node, bool departure);