From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Sat, 16 Oct 2021 17:38:35 -0700
Subject: [PATCH] Use correct LevelStem registry when loading default
 end/nether

Co-authored-by: Jake Potrebic <jake.m.potrebic@gmail.com>

diff --git a/src/main/java/net/minecraft/resources/RegistryLoader.java b/src/main/java/net/minecraft/resources/RegistryLoader.java
index 75f72b568ee2b27c5042da688b62d4e3c5732e09..8c3555842202d67793d818c96feda4daa2f08a0c 100644
--- a/src/main/java/net/minecraft/resources/RegistryLoader.java
+++ b/src/main/java/net/minecraft/resources/RegistryLoader.java
@@ -42,6 +42,12 @@ public class RegistryLoader {
         RegistryLoader.ReadCache<E> readCache = this.readCache(registryRef);
         DataResult<Holder<E>> dataResult = readCache.values.get(entryKey);
         if (dataResult != null) {
+            // Paper start - register in registry due to craftbukkit running this 3 times instead of once
+            if (registryRef == (ResourceKey) Registry.LEVEL_STEM_REGISTRY && dataResult.result().isPresent()) {
+                // OptionalInt.empty() because the LevelStem registry is only loaded from the resource manager, not the InMemory resource access
+                registry.registerOrOverride(java.util.OptionalInt.empty(), entryKey, dataResult.result().get().value(), dataResult.lifecycle());
+            }
+            // Paper end
             return dataResult;
         } else {
             Holder<E> holder = registry.getOrCreateHolder(entryKey);
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index fddb279d161b30d6944495f0de9f6b7e21761a80..df955666723a8cb1e612311f0b8e77fb577d6be5 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -563,7 +563,14 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             long i = generatorsettings.seed();
             long j = BiomeManager.obfuscateSeed(i);
             List<CustomSpawner> list = ImmutableList.of(new PhantomSpawner(), new PatrolSpawner(), new CatSpawner(), new VillageSiege(), new WanderingTraderSpawner(iworlddataserver));
-            LevelStem worlddimension = (LevelStem) iregistry.get(dimensionKey);
+            // Paper start - Use correct LevelStem registry
+            final LevelStem worlddimension;
+            if (dimensionKey == LevelStem.END || dimensionKey == LevelStem.NETHER) {
+                worlddimension = generatorsettings.dimensions().get(dimensionKey);
+            } else {
+                worlddimension = iregistry.get(dimensionKey);
+            }
+            // Paper end
             Holder<DimensionType> holder;
             ChunkGenerator chunkgenerator;