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 9c0cc06f4ebbfbd7959f05cae12a9f9e7e622c04..0d4e641187b305c4b56782b4c70bca39efcaa69c 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -657,7 +657,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 return;
             }
 
-            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 moveTo for teleportation
             this.lastGoodX = this.awaitingPositionFromClient.x;
             this.lastGoodY = this.awaitingPositionFromClient.y;
             this.lastGoodZ = this.awaitingPositionFromClient.z;
@@ -1587,7 +1587,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         // 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 moveTo for teleportation
         this.player.connection.send(new ClientboundPlayerPositionPacket(d0 - d3, d1 - d4, d2 - d5, f - f2, f1 - f3, set, this.awaitingTeleport));
     }
 
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 0924677535ba455a2118f7022bdd361c609022d4..452789dc47393580374bf438e6229b1e6cd3832b 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -160,6 +160,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     // 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;
     }
@@ -1869,6 +1870,13 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
     }
 
     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 41f549f16f69f9bc50a004096e6c3c0f6e4d4eaf..9ec83d6eeff22c2ce25374a83f581a675d4fd067 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -169,6 +169,7 @@ public abstract class BaseSpawner {
                             return;
                         }
 
+                        entity.preserveMotion = true; // Paper - preserve entity motion from tag
                         entity.moveTo(entity.getX(), entity.getY(), entity.getZ(), randomsource.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 c17bb16567ad2354dc80e710469730b1dbc55b08..d5e8c8ed7528cdac203a7594ccf9576db0e5f019 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -237,7 +237,7 @@ 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 moveTo, as per vanilla teleporting
         // SPIGOT-619: Force sync head rotation also
         this.entity.setYHeadRot(location.getYaw());