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 83a469447e39b801442769fcb5979e987e2adae9..e65cb9c72e46d50b871d1c7b5789a1855622d934 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;
     }
@@ -1317,6 +1318,13 @@ 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 f1e3c764fc8d5b6acb2ae94276e31fe37af817b6..5af38d36f64020d1df492ad57fafd2baf867536a 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -542,7 +542,7 @@ 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;
@@ -1386,7 +1386,7 @@ 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 c7636ffc952c436d7148e6e5926b0108cc628821..582ed13a9ba1748444ce4d624d83a4d7be7006f2 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -554,7 +554,7 @@ 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