From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@users.noreply.github.com>
Date: Fri, 4 Jun 2021 17:06:52 -0400
Subject: [PATCH] Fix dangerous end portal logic

End portals could teleport entities during move calls. Stupid
logic given the caller will never expect that kind of thing,
and will result in all kinds of dupes.

Move the tick logic into the post tick, where portaling was
designed to happen in the first place.

diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 968d231c8f6762a2f6177897c3b5f24864d60152..bbd071009d9ccf84f4c4ade296c98a8f4d6ac3ae 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -485,6 +485,36 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
     // Paper end
     // Paper start - optimise entity tracking
     final org.spigotmc.TrackingRange.TrackingRangeType trackingRangeType = org.spigotmc.TrackingRange.getTrackingRangeType(this);
+    // Paper start - make end portalling safe
+    public BlockPos portalBlock;
+    public ServerLevel portalWorld;
+    public void tickEndPortal() {
+        BlockPos pos = this.portalBlock;
+        ServerLevel world = this.portalWorld;
+        this.portalBlock = null;
+        this.portalWorld = null;
+
+        if (pos == null || world == null || world != this.level) {
+            return;
+        }
+
+        if (this.isPassenger() || this.isVehicle() || !this.canChangeDimensions() || this.isRemoved() || !this.valid || !this.isAlive()) {
+            return;
+        }
+
+        ResourceKey<Level> resourcekey = world.getTypeKey() == LevelStem.END ? Level.OVERWORLD : Level.END; // CraftBukkit - SPIGOT-6152: send back to main overworld in custom ends
+        ServerLevel worldserver = world.getServer().getLevel(resourcekey);
+
+        org.bukkit.event.entity.EntityPortalEnterEvent event = new org.bukkit.event.entity.EntityPortalEnterEvent(this.getBukkitEntity(), new org.bukkit.Location(world.getWorld(), pos.getX(), pos.getY(), pos.getZ()));
+        event.callEvent();
+
+        if (this instanceof ServerPlayer) {
+            ((ServerPlayer)this).changeDimension(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
+            return;
+        }
+        this.teleportTo(worldserver, null);
+    }
+    // Paper end - make end portalling safe
 
     public boolean isLegacyTrackingEntity = false;
 
@@ -2871,6 +2901,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
             }
 
             this.processPortalCooldown();
+            this.tickEndPortal(); // Paper - make end portalling safe
         }
     }
 
diff --git a/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java b/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
index 45b427f314da778cc13da9ad6e4e1316790bf1b1..41d7cff39fc37955877668337689b4b26cd8c7cf 100644
--- a/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
@@ -53,16 +53,10 @@ public class EndPortalBlock extends BaseEntityBlock {
                 // return; // CraftBukkit - always fire event in case plugins wish to change it
             }
 
-            // CraftBukkit start - Entity in portal
-            EntityPortalEnterEvent event = new EntityPortalEnterEvent(entity.getBukkitEntity(), new org.bukkit.Location(world.getWorld(), pos.getX(), pos.getY(), pos.getZ()));
-            world.getCraftServer().getPluginManager().callEvent(event);
-
-            if (entity instanceof ServerPlayer) {
-                ((ServerPlayer) entity).changeDimension(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
-                return;
-            }
-            // CraftBukkit end
-            entity.changeDimension(worldserver);
+            // Paper start - move all of this logic into portal tick
+            entity.portalWorld = ((ServerLevel)world);
+            entity.portalBlock = pos.immutable();
+            // Paper end - move all of this logic into portal tick
         }
 
     }