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/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index a80781a0525ef5b46a7c9af3011dab6662f06016..be682e8459bb7293256c3552d90f5cdb8d97a29d 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -681,7 +681,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Ser
     public void handleAcceptTeleportPacket(ServerboundAcceptTeleportationPacket packet) {
         PacketUtils.ensureRunningOnSameThread(packet, this, this.player.getLevel());
         if (packet.getId() == this.awaitingTeleport && this.awaitingPositionFromClient != null) { // CraftBukkit
-            this.player.absMoveTo(this.awaitingPositionFromClient.x, this.awaitingPositionFromClient.y, this.awaitingPositionFromClient.z, this.player.getYRot(), this.player.getXRot());
+            this.player.moveTo(this.awaitingPositionFromClient.x, this.awaitingPositionFromClient.y, this.awaitingPositionFromClient.z, this.player.getYRot(), this.player.getXRot()); // Paper - use proper setPositionRotation for teleportation
             this.lastGoodX = this.awaitingPositionFromClient.x;
             this.lastGoodY = this.awaitingPositionFromClient.y;
             this.lastGoodZ = this.awaitingPositionFromClient.z;
@@ -1548,7 +1548,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Ser
         // CraftBukkit end
 
         this.awaitingTeleportTime = this.tickCount;
-        this.player.absMoveTo(d0, d1, d2, f, f1);
+        this.player.moveTo(d0, d1, d2, f, f1); // Paper - use proper setPositionRotation for teleportation
         this.player.forceCheckHighPriority(); // Paper
         this.player.connection.send(new ClientboundPlayerPositionPacket(d0 - d3, d1 - d4, d2 - d5, f - f2, f1 - f3, set, this.awaitingTeleport, flag));
     }
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 8df955a0aa6cd0c7d10619fb63abd16af4754be8..a652bbc4b3c768fecfb6f067d21a90315256f885 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -152,6 +152,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, n
 
     // CraftBukkit start
     private static final int CURRENT_LEVEL = 2;
+    public boolean preserveMotion = true; // Paper - keep initial motion on first setPositionRotation
     static boolean isLevelAtLeast(CompoundTag tag, int level) {
         return tag.contains("Bukkit.updateLevel") && tag.getInt("Bukkit.updateLevel") >= level;
     }
@@ -1568,6 +1569,13 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, n
     }
 
     public void moveTo(double x, double y, double z, float yaw, float pitch) {
+        // Paper - cancel entity velocity if teleported
+        if (!preserveMotion) {
+            this.deltaMovement = Vec3.ZERO;
+        } else {
+            this.preserveMotion = false;
+        }
+        // Paper end
         this.setPosRaw(x, y, z);
         this.setYRot(yaw);
         this.setXRot(pitch);
diff --git a/src/main/java/net/minecraft/world/level/BaseSpawner.java b/src/main/java/net/minecraft/world/level/BaseSpawner.java
index b9e738542692aba7b78fc514ae8e3248df9998ea..c601b8b12756682a4cb300be8ebed4319902c5b5 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -170,6 +170,7 @@ public abstract class BaseSpawner {
                             return;
                         }
 
+                        entity.preserveMotion = true; // Paper - preserve entity motion from tag
                         entity.moveTo(entity.getX(), entity.getY(), entity.getZ(), world.random.nextFloat() * 360.0F, 0.0F);
                         if (entity instanceof Mob) {
                             Mob entityinsentient = (Mob) entity;
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index f28f857d6218db1634348e8a57e7b275b9115bfc..a0a24a46624b3d174d08c806c8ad45d8a9028a09 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -577,7 +577,7 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         }
 
         // entity.setLocation() throws no event, and so cannot be cancelled
-        this.entity.absMoveTo(location.getX(), location.getY(), location.getZ(), location.getYaw(), location.getPitch());
+        entity.moveTo(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
         this.entity.setYHeadRot(location.getYaw());