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/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 3e6ccdd5b54dbe51d4ee9ec979cbc2d0f335be70..5e1978d1c96dede07ead967c1e85a352348e7777 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -54,6 +54,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
 
     // 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;
     }
@@ -1316,6 +1317,13 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
     }
 
     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/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
index 16664a446192c77903ff1f10989c7afab703eb49..05b3a7478195037927cd1a902b603862d9747e61 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -501,7 +501,7 @@ 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;
@@ -1302,7 +1302,7 @@ 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/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index b1fdc5737d332c6210d57793468da1eda8f8b9d2..6ceb2d50c59b63a337364605f8a5280d905f2662 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -547,7 +547,7 @@ 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.WorldServer) entity.world).chunkCheck(entity); // Spigot - register to new chunk