Corrected issues with worldGenContext not correctly being set (Ref: https://stackoverflow.com/questions/56039341/get-declared-fields-of-java-lang-reflect-fields-in-jdk12/56043252#56043252)

common/api/src/main/java/com/dfsek/terra/api/util/reflection/ReflectionUtil.java

@@ -8,6 +8,7 @@
 package com.dfsek.terra.api.util.reflection;
 
 import org.jetbrains.annotations.NotNull;
+import sun.misc.Unsafe;
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.AnnotatedElement;
@@ -26,6 +27,18 @@ import java.util.stream.Stream;
 
 
 public final class ReflectionUtil {
+    private static final Unsafe UNSAFE;
+
+    static {
+        try{
+            final Field unsafeField = Unsafe.class.getDeclaredField("theUnsafe");
+            unsafeField.setAccessible(true);
+            UNSAFE = (Unsafe) unsafeField.get(null);
+        } catch(NoSuchFieldException | IllegalAccessException e){
+            throw new RuntimeException(e);
+        }
+    }
+
     public static Field[] getFields(@NotNull Class<?> type) {
         Field[] result = type.getDeclaredFields();
         Class<?> parentClass = type.getSuperclass();
@@ -35,6 +48,14 @@ public final class ReflectionUtil {
         return result;
     }
 
+    public static void setFinalField(Object obj, String fieldName, Object value) throws NoSuchFieldException {
+        Field field = obj.getClass().getDeclaredField(fieldName);
+        field.setAccessible(true);
+        long fieldOffset = UNSAFE.objectFieldOffset(field);
+
+        UNSAFE.putObject(obj, fieldOffset, value);
+    }
+
     public static Method[] getMethods(@NotNull Class<?> type) {
         Method[] result = type.getDeclaredMethods();
         Class<?> parentClass = type.getSuperclass();

platforms/bukkit/nms/v1_21/src/main/java/com/dfsek/terra/bukkit/nms/v1_21/NMSInjectListener.java

@@ -1,9 +1,12 @@
 package com.dfsek.terra.bukkit.nms.v1_21;
 
+import com.dfsek.terra.api.util.reflection.ReflectionUtil;
+
 import net.minecraft.server.level.ChunkMap;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.level.chunk.ChunkGenerator;
 import net.minecraft.world.level.chunk.status.WorldGenContext;
+import org.bukkit.Bukkit;
 import org.bukkit.World;
 import org.bukkit.craftbukkit.CraftWorld;
 import org.bukkit.event.EventHandler;
@@ -12,7 +15,6 @@ import org.bukkit.event.world.WorldInitEvent;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.lang.reflect.Field;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.concurrent.locks.ReentrantLock;
@@ -41,21 +43,17 @@ public class NMSInjectListener implements Listener {
             ChunkGenerator vanilla = serverWorld.getChunkSource().getGenerator();
             NMSBiomeProvider provider = new NMSBiomeProvider(pack.getBiomeProvider(), craftWorld.getSeed());
             ChunkMap chunkMap = serverWorld.getChunkSource().chunkMap;
+            WorldGenContext worldGenContext = chunkMap.worldGenContext;
 
             try {
-                Field worldGenContextField = chunkMap.getClass().getDeclaredField("worldGenContext");
+                ReflectionUtil.setFinalField(chunkMap, "worldGenContext", new WorldGenContext(
-                worldGenContextField.setAccessible(true);
+                    worldGenContext.level(),
-
+                    new NMSChunkGeneratorDelegate(vanilla, pack, provider, craftWorld.getSeed()),
-                WorldGenContext worldGenContext = (WorldGenContext) worldGenContextField.get(chunkMap);
+                    worldGenContext.structureManager(),
-                worldGenContextField.set(chunkMap,
+                    worldGenContext.lightEngine(),
-                    new WorldGenContext(
+                    worldGenContext.mainThreadMailBox()
-                        worldGenContext.level(),
+                ));
-                        new NMSChunkGeneratorDelegate(vanilla, pack, provider, craftWorld.getSeed()),
+            } catch(NoSuchFieldException e) {
-                        worldGenContext.structureManager(),
-                        worldGenContext.lightEngine(),
-                        worldGenContext.mainThreadMailBox()
-                    ));
-            } catch(NoSuchFieldException | IllegalAccessException e) {
                 throw new RuntimeException(e);
             }