Fix dangerous end portal logic (#5776)

Co-authored-by: Spottedleaf <Spottedleaf@users.noreply.github.com>

Spigot-Server-Patches/0655-added-Wither-API.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] added Wither API
 
 
 diff --git a/src/main/java/net/minecraft/world/entity/boss/wither/EntityWither.java b/src/main/java/net/minecraft/world/entity/boss/wither/EntityWither.java
-index 30290c0208a4725b2eb0e7764465c354e592e4ee..891905712903bf3ba241187791cfa995375430d5 100644
+index 30290c0208a4725b2eb0e7764465c354e592e4ee..170b085c76e092f6d7b14095c66c84fa9a96a1fc 100644
 --- a/src/main/java/net/minecraft/world/entity/boss/wither/EntityWither.java
 +++ b/src/main/java/net/minecraft/world/entity/boss/wither/EntityWither.java
 @@ -82,6 +82,11 @@ public class EntityWither extends EntityMonster implements IRangedEntity {
@@ -33,7 +33,7 @@ index 30290c0208a4725b2eb0e7764465c354e592e4ee..891905712903bf3ba241187791cfa995
      @Override
      public boolean canPortal() {
 -        return false;
-+        return canPortal; // Paper
++        return super.canPortal() && canPortal; // Paper
      }
  
      @Override

Spigot-Server-Patches/0755-Fix-dangerous-end-portal-logic.patch

@@ -0,0 +1,99 @@
+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/server/level/EntityPlayer.java b/src/main/java/net/minecraft/server/level/EntityPlayer.java
+index 558af73ac16550ee6964c4dce681a404633b2552..75bcfb3a2b4a104aeebb2fe3298714b2e5b569d2 100644
+--- a/src/main/java/net/minecraft/server/level/EntityPlayer.java
++++ b/src/main/java/net/minecraft/server/level/EntityPlayer.java
+@@ -1023,6 +1023,7 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
+         return b(worldserver, TeleportCause.UNKNOWN);
+     }
+ 
++    @Nullable public final Entity changeDimension(WorldServer worldserver, PlayerTeleportEvent.TeleportCause cause) { return this.b(worldserver, cause); } // Paper - OBFHELPER
+     @Nullable
+     public Entity b(WorldServer worldserver, PlayerTeleportEvent.TeleportCause cause) {
+         // CraftBukkit end
+diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
+index 6fdcd96fd75cd63d769b012827519f554af4cf54..8ef41182056052686055b7eb88ab19c161e84ed4 100644
+--- a/src/main/java/net/minecraft/world/entity/Entity.java
++++ b/src/main/java/net/minecraft/world/entity/Entity.java
+@@ -314,6 +314,37 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
+     }
+     // Paper end - optimise entity tracking
+ 
++    // Paper start - make end portalling safe
++    public BlockPosition portalBlock;
++    public WorldServer portalWorld;
++    public void tickEndPortal() {
++        BlockPosition pos = this.portalBlock;
++        WorldServer world = this.portalWorld;
++        this.portalBlock = null;
++        this.portalWorld = null;
++
++        if (pos == null || world == null || world != this.world) {
++            return;
++        }
++
++        if (this.isPassenger() || this.isVehicle() || !this.canPortal() || this.dead || !this.valid || !this.isAlive()) {
++            return;
++        }
++
++        ResourceKey<World> resourcekey = world.getTypeKey() == DimensionManager.THE_END ? World.OVERWORLD : World.THE_END; // CraftBukkit - SPIGOT-6152: send back to main overworld in custom ends
++        WorldServer worldserver = world.getMinecraftServer().getWorldServer(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 EntityPlayer) {
++            ((EntityPlayer)this).changeDimension(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
++            return;
++        }
++        this.teleportTo(worldserver, null);
++    }
++    // Paper end - make end portalling safe
++
+     public Entity(EntityTypes<?> entitytypes, World world) {
+         this.id = Entity.entityCount.incrementAndGet();
+         this.passengers = Lists.newArrayList();
+@@ -2294,6 +2325,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
+             }
+ 
+             this.E();
++            this.tickEndPortal(); // Paper - make end portalling safe
+         }
+     }
+ 
+diff --git a/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java b/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java
+index ed916f69747b44b75eb06db4cf27adaf5e47fd1e..9483d75fbe2a8c8f7cce00355e93ff1f943f3444 100644
+--- a/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java
++++ b/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java
+@@ -52,16 +52,10 @@ public class BlockEnderPortal extends BlockTileEntity {
+                 // 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(), blockposition.getX(), blockposition.getY(), blockposition.getZ()));
+-            world.getServer().getPluginManager().callEvent(event);
+-
+-            if (entity instanceof EntityPlayer) {
+-                ((EntityPlayer) entity).b(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
+-                return;
+-            }
+-            // CraftBukkit end
+-            entity.b(worldserver);
++            // Paper start - move all of this logic into portal tick
++            entity.portalWorld = ((WorldServer)world);
++            entity.portalBlock = blockposition.immutableCopy();
++            // Paper end - move all of this logic into portal tick
+         }
+ 
+     }