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 b7454592b9cee09f41631db6664cb18e2f890479..b45f79e83fc033424472b4044ab15a8c93cb0aec 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.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 73fc8ebd2ec207db2efc545f6bb304d53880b78f..bf1f22ee4e2a38b0fe2430dbeb20ae9f544ea423 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;
     }
@@ -1545,6 +1546,13 @@ 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 17ad49994499982a08c1e8a4b4635647d669986a..187504b19f0194c700b5e498be191cf58b8d34ad 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -567,7 +567,7 @@ 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());