From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Tue, 25 Aug 2020 20:45:36 -0400
Subject: [PATCH] Fix Entity Teleportation and cancel velocity if teleported

Uses correct setPositionRotation for Entity teleporting instead of setLocation
as this is how Vanilla teleports entities.

Cancel any pending motion when teleported.

diff --git a/src/main/java/net/minecraft/server/network/PlayerConnection.java b/src/main/java/net/minecraft/server/network/PlayerConnection.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/network/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/network/PlayerConnection.java
@@ -0,0 +0,0 @@ public class PlayerConnection implements PacketListenerPlayIn {
     public void a(PacketPlayInTeleportAccept packetplayinteleportaccept) {
         PlayerConnectionUtils.ensureMainThread(packetplayinteleportaccept, this, this.player.getWorldServer());
         if (packetplayinteleportaccept.b() == this.teleportAwait && this.teleportPos != null) { // CraftBukkit
-            this.player.setLocation(this.teleportPos.x, this.teleportPos.y, this.teleportPos.z, this.player.yaw, this.player.pitch);
+            this.player.setPositionRotation(this.teleportPos.x, this.teleportPos.y, this.teleportPos.z, this.player.yaw, this.player.pitch); // Paper - use proper setPositionRotation for teleportation
             this.o = this.teleportPos.x;
             this.p = this.teleportPos.y;
             this.q = this.teleportPos.z;
@@ -0,0 +0,0 @@ public class PlayerConnection implements PacketListenerPlayIn {
         // CraftBukkit end
 
         this.A = this.e;
-        this.player.setLocation(d0, d1, d2, f, f1);
+        this.player.setPositionRotation(d0, d1, d2, f, f1); // Paper - use proper setPositionRotation for teleportation
         this.player.forceCheckHighPriority(); // Paper
         this.player.playerConnection.sendPacket(new PacketPlayOutPosition(d0 - d3, d1 - d4, d2 - d5, f - f2, f1 - f3, set, this.teleportAwait));
     }
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -0,0 +0,0 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
 
     // CraftBukkit start
     private static final int CURRENT_LEVEL = 2;
+    boolean preserveMotion = true; // Paper - keep initial motion on first setPositionRotation
     static boolean isLevelAtLeast(NBTTagCompound tag, int level) {
         return tag.hasKey("Bukkit.updateLevel") && tag.getInt("Bukkit.updateLevel") >= level;
     }
@@ -0,0 +0,0 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
     }
 
     public void setPositionRotation(double d0, double d1, double d2, float f, float f1) {
+        // Paper - cancel entity velocity if teleported
+        if (!preserveMotion) {
+            this.mot = Vec3D.ORIGIN;
+        } else {
+            this.preserveMotion = false;
+        }
+        // Paper end
         this.g(d0, d1, d2);
         this.yaw = f;
         this.pitch = f1;
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -0,0 +0,0 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         }
 
         // entity.setLocation() throws no event, and so cannot be cancelled
-        entity.setLocation(location.getX(), location.getY(), location.getZ(), location.getYaw(), location.getPitch());
+        entity.setPositionRotation(location.getX(), location.getY(), location.getZ(), location.getYaw(), location.getPitch()); // Paper - use proper setPosition, as per vanilla teleporting
         // SPIGOT-619: Force sync head rotation also
         entity.setHeadRotation(location.getYaw());
         ((net.minecraft.server.level.WorldServer) entity.world).chunkCheck(entity); // Spigot - register to new chunk