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 8da1226a6c293abb038d10c7921a77ed71ad06cc..f958f0ae738a6fb26400e17e54c8d69e95268cdd 100644
--- a/src/main/java/net/minecraft/resources/RegistryLoader.java
+++ b/src/main/java/net/minecraft/resources/RegistryLoader.java
@@ -46,6 +46,12 @@ 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.getOrCreateHolderOrThrow(entryKey);
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 621956c024d64bcaa868e0bb01c485fe4ac11df3..002daab4b5bb32cdab9f822d8229805a8ab36ded 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -553,7 +553,14 @@ 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
 
             org.bukkit.generator.WorldInfo worldInfo = new org.bukkit.craftbukkit.generator.CraftWorldInfo(iworlddataserver, worldSession, org.bukkit.World.Environment.getEnvironment(dimension), worlddimension.typeHolder().value());
             if (biomeProvider == null && gen != null) {
