Paper/patches/unapplied/server/0647-Fix-dangerous-end-portal-logic.patch

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 0624f832f301ec2a36085e66f67b6a529583a496..6b6de6812740357d4c2c8bca0c064aa52e61fa60 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -509,6 +509,36 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         return chunkMap.playerEntityTrackerTrackMaps[type.ordinal()].getObjectsInRange(MCUtil.getCoordinateKey(this));
     }
     // Paper end - optimise entity tracking
+    // 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 Entity(EntityType<?> type, Level world) {
         this.id = Entity.ENTITY_COUNTER.incrementAndGet();
@@ -2685,6 +2715,7 @@ 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 150c16da7caa655cfc2c371d3336a8d7345438c6..15c5cccfe02c924c02f605eb47dd0b420b189891 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
         }
 
     }