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 eab19d5ac362c4779e91fad0ede3e4c26f29ab01..0d7dae5fa79cd302d73d1be51d8bf908a816c4ca 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -680,7 +680,7 @@ 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 - Fix Entity Teleportation and cancel velocity if teleported
             this.lastGoodX = this.awaitingPositionFromClient.x;
             this.lastGoodY = this.awaitingPositionFromClient.y;
             this.lastGoodZ = this.awaitingPositionFromClient.z;
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 3860265a50b62fbd36c9e1b32680c3b62d5342a6..e93f8a9eefc082d66d0e1804c98d0df7db914cd8 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -180,6 +180,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
 
     // CraftBukkit start
     private static final int CURRENT_LEVEL = 2;
+    public boolean preserveMotion = true; // Paper - Fix Entity Teleportation and cancel velocity if teleported; keep initial motion on first setPositionRotation
     static boolean isLevelAtLeast(CompoundTag tag, int level) {
         return tag.contains("Bukkit.updateLevel") && tag.getInt("Bukkit.updateLevel") >= level;
     }
@@ -1967,6 +1968,13 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
     }
 
     public void moveTo(double x, double y, double z, float yaw, float pitch) {
+        // Paper start - Fix Entity Teleportation and cancel velocity if teleported
+        if (!preserveMotion) {
+            this.deltaMovement = Vec3.ZERO;
+        } else {
+            this.preserveMotion = false;
+        }
+        // Paper end - Fix Entity Teleportation and cancel velocity if teleported
         this.setPosRaw(x, y, z);
         this.setYRot(yaw);
         this.setXRot(pitch);
diff --git a/src/main/java/net/minecraft/world/entity/boss/enderdragon/phases/DragonStrafePlayerPhase.java b/src/main/java/net/minecraft/world/entity/boss/enderdragon/phases/DragonStrafePlayerPhase.java
index 2db75673e525708d04bda9f6c9af80e7f8d361e6..be2b5f56f6f29c82c4fa9df33287d0ddb589f383 100644
--- a/src/main/java/net/minecraft/world/entity/boss/enderdragon/phases/DragonStrafePlayerPhase.java
+++ b/src/main/java/net/minecraft/world/entity/boss/enderdragon/phases/DragonStrafePlayerPhase.java
@@ -79,6 +79,7 @@ public class DragonStrafePlayerPhase extends AbstractDragonPhaseInstance {
                         }
 
                         DragonFireball dragonFireball = new DragonFireball(world, this.dragon, vec34.normalize());
+                        dragonFireball.preserveMotion = true; // Paper - Fix Entity Teleportation and cancel velocity if teleported
                         dragonFireball.moveTo(o, p, q, 0.0F, 0.0F);
                         if (new com.destroystokyo.paper.event.entity.EnderDragonShootFireballEvent((org.bukkit.entity.EnderDragon) dragon.getBukkitEntity(), (org.bukkit.entity.DragonFireball) dragonFireball.getBukkitEntity()).callEvent()) // Paper - EnderDragon Events
                         world.addFreshEntity(dragonFireball);
diff --git a/src/main/java/net/minecraft/world/level/BaseSpawner.java b/src/main/java/net/minecraft/world/level/BaseSpawner.java
index 56dbe701a93eb9f1309bec92e5d3b310860a4dc5..1b6ec72f59504d2f420d6d5dcbed4d3b9115e3d8 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -164,6 +164,7 @@ public abstract class BaseSpawner {
                             return;
                         }
 
+                        entity.preserveMotion = true; // Paper - Fix Entity Teleportation and cancel velocity if teleported; 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 ec122fa4e443290ff973797740172e07f8e736ca..609c768ba4d22e346acbc9422ce41e3b887fadb1 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -241,7 +241,7 @@ 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());
 
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
index 0aa3fd9dce0cf90b1f74551c864e9ebf326eb1f3..e979681142bd08aeb00a98b79789a8f41b2a37af 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java
@@ -603,6 +603,7 @@ public class CraftLivingEntity extends CraftEntity implements LivingEntity {
             }
 
             ((AbstractHurtingProjectile) launch).projectileSource = this;
+            launch.preserveMotion = true; // Paper - Fix Entity Teleportation and cancel velocity if teleported
             launch.moveTo(location.getX(), location.getY(), location.getZ(), location.getYaw(), location.getPitch());
         } else if (LlamaSpit.class.isAssignableFrom(projectile)) {
             Location location = this.getEyeLocation();