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 1d154ef60fd979340cf925748251669e860d4094..68f8a7f227c4d683d4c13d634ccfbabe759e82b3 100644
--- a/src/main/java/net/minecraft/server/network/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/network/PlayerConnection.java
@@ -693,7 +693,7 @@ 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;
@@ -1537,7 +1537,7 @@ 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/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 743d4725c0a26a8abd0a98eed2ec45ffba6211ad..344862c3f479ae7b6d4f929c9ef7882aba983ffb 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -145,6 +145,7 @@ 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;
     }
@@ -1408,6 +1409,13 @@ 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 387f6f6fa9bbb1cce544cfb907f68c7993752dd7..fb52a60437d48282f3e99e7eccb0e76b446155f9 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -558,7 +558,7 @@ 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.level.WorldServer) entity.world).chunkCheck(entity); // Spigot - register to new chunk