Requested changes

src/main/java/io/github/opencubicchunks/cubicchunks/core/asm/mixin/core/common/MixinWorldServer.java

@@ -46,6 +46,7 @@
 import io.github.opencubicchunks.cubicchunks.core.server.PlayerCubeMap;
 import io.github.opencubicchunks.cubicchunks.core.server.SpawnCubes;
 import io.github.opencubicchunks.cubicchunks.core.server.VanillaNetworkHandler;
+import io.github.opencubicchunks.cubicchunks.core.util.CompatHandler;
 import io.github.opencubicchunks.cubicchunks.core.util.world.CubeSplitTickList;
 import io.github.opencubicchunks.cubicchunks.core.util.world.CubeSplitTickSet;
 import io.github.opencubicchunks.cubicchunks.core.world.CubeWorldEntitySpawner;
@@ -117,8 +118,6 @@ public abstract class MixinWorldServer extends MixinWorld implements ICubicWorld
 
     @Shadow protected abstract void playerCheckLight();
 
-    @Shadow public abstract boolean spawnEntity(Entity entityIn);
-
     @Shadow public abstract boolean addWeatherEffect(Entity entityIn);
 
     @Shadow @Mutable @Final private Set<NextTickListEntry> pendingTickListEntriesHashSet;
@@ -368,7 +367,7 @@ private void tickColumn(boolean raining, boolean thundering, Chunk chunk) {
                     skeletonHorse.setTrap(true);
                     skeletonHorse.setGrowingAge(0);
                     skeletonHorse.setPosition((double) strikePos.getX(), (double) strikePos.getY(), (double) strikePos.getZ());
-                    this.spawnEntity(skeletonHorse);
+                    CompatHandler.spawnEntity(skeletonHorse, (WorldServer) (Object) this);
                     this.addWeatherEffect(new EntityLightningBolt((World) (Object) this,
                             (double) strikePos.getX(), (double) strikePos.getY(), (double) strikePos.getZ(), true));
                 } else {

src/main/java/io/github/opencubicchunks/cubicchunks/core/util/CompatHandler.java

@@ -24,8 +24,8 @@
  */
 package io.github.opencubicchunks.cubicchunks.core.util;
 
+import java.lang.invoke.MethodHandle;
 import java.lang.reflect.Constructor;
-import java.lang.reflect.Field;
 import java.util.AbstractMap;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -43,7 +43,9 @@
 import io.github.opencubicchunks.cubicchunks.core.asm.mixin.ICubicWorldInternal;
 import io.github.opencubicchunks.cubicchunks.core.asm.mixin.fixes.common.fakeheight.IASMEventHandler;
 import io.github.opencubicchunks.cubicchunks.core.asm.mixin.fixes.common.fakeheight.IEventBus;
+import net.minecraft.entity.Entity;
 import net.minecraft.world.World;
+import net.minecraft.world.WorldServer;
 import net.minecraft.world.chunk.Chunk;
 import net.minecraft.world.gen.IChunkGenerator;
 import net.minecraftforge.common.MinecraftForge;
@@ -56,6 +58,7 @@
 import net.minecraftforge.fml.common.eventhandler.EventBus;
 import net.minecraftforge.fml.common.eventhandler.IEventListener;
 import net.minecraftforge.fml.common.eventhandler.ListenerList;
+import org.bukkit.event.entity.CreatureSpawnEvent;
 
 public class CompatHandler {
 
@@ -290,4 +293,24 @@ private static <T> IEventListener[] getFakeEventListeners(ListenerList listenerL
 
         return newList.toArray(new IEventListener[0]);
     }
+
+    /*
+     * Hybrid servers do have this method in World class, but not in WorldServer.
+     */
+    public static boolean spawnEntity(Entity entity, WorldServer world) {
+        if (PlatformCompatUtils.isHybridEnv() && MH_WorldServer_Bukkit_addEntity != null) {
+            try {
+                return (boolean) MH_WorldServer_Bukkit_addEntity.invokeExact(world, entity, CreatureSpawnEvent.SpawnReason.DEFAULT);
+            } catch (Throwable th) {
+                CubicChunks.LOGGER.error("Failed to call WorldServer.addEntity", th);
+                return false;
+            }
+        }
+        return world.spawnEntity(entity);
+    }
+
+    // MethodHandle for WorldServer#addEntity(Entity, CreatureSpawnEvent.SpawnReason) method in CraftBukkit
+    private static final MethodHandle MH_WorldServer_Bukkit_addEntity = ReflectionUtil.methodHandle(true, WorldServer.class, "addEntity",
+            Entity.class,
+            ReflectionUtil.getClass("org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason"));
 }

src/main/java/io/github/opencubicchunks/cubicchunks/core/util/PlatformCompatUtils.java

@@ -28,17 +28,22 @@ public class PlatformCompatUtils {
     private PlatformCompatUtils() {
     }
 
-    private static final boolean isHybridEnv = isClassLoaded("org.bukkit.Bukkit");
+    private static final boolean isHybridEnv = isClassExists("org.bukkit.Bukkit");
 
-    public static boolean isClassLoaded(String name) {
+    public static boolean isClassLoaded(String className) {
         try {
-            Class.forName(name);
+            Class.forName(className);
             return true;
         } catch (ClassNotFoundException e) {
             return false;
         }
     }
 
+    public static boolean isClassExists(String className) {
+        String classPath = className.replace('.', '/') + ".class";
+        return Thread.currentThread().getContextClassLoader().getResource(classPath) != null;
+    }
+
     public static boolean isHybridEnv() {
         return isHybridEnv;
     }

src/main/java/io/github/opencubicchunks/cubicchunks/core/util/ReflectionUtil.java

@@ -30,6 +30,8 @@
 import java.lang.invoke.MethodHandles;
 import java.lang.reflect.Constructor;
 
+import javax.annotation.CheckForNull;
+import javax.annotation.Nullable;
 import javax.annotation.ParametersAreNonnullByDefault;
 
 @ParametersAreNonnullByDefault
@@ -65,4 +67,36 @@ public static MethodHandle constructHandle(Class<?> owner, Class<?>... args) {
             throw new Error(e);
         }
     }
+
+    /**
+     * Returns a method handle for a method of a class.
+     *
+     * @param suppressException if true, returns null if the method is not found instead of throwing error
+     * @param owner the class
+     * @param name the method name
+     * @param args the method arguments
+     * @return the method handle, or null if not found and suppressException is true
+     */
+    @CheckForNull
+    public static MethodHandle methodHandle(boolean suppressException, Class<?> owner, String name, Class<?>... args) {
+        for (Class<?> clazz : args) {
+            if (clazz == null) return null;
+        }
+        try {
+            return MethodHandles.lookup().unreflect(owner.getDeclaredMethod(name, args));
+        } catch (Exception e) {
+            if (suppressException) return null;
+            //if it happens - either something has gone horribly wrong or the JVM is blocking access
+            throw new Error(e);
+        }
+    }
+
+    @Nullable
+    public static Class<?> getClass(String className) {
+        try {
+            return Class.forName(className);
+        } catch (ClassNotFoundException e) {
+            return null;
+        }
+    }
 }

src/main/resources/cubicchunks.mixins.core.bukkit.json

@@ -12,7 +12,6 @@
     "server": [
         "common.MixinWorld_HeightLimits_Bukkit_Sided",
         "common.MixinPlayerList_Bukkit_Sided",
-        "common.MixinChunk_Cubes_Bukkit_Sided",
-        "common.MixinWorldServer_Bukkit"
+        "common.MixinChunk_Cubes_Bukkit_Sided"
     ]
 }

src/main/resources/cubicchunks.mixins.core.json

@@ -37,6 +37,7 @@
         "common.MixinWorldEntitySpawner",
         "common.MixinWorldInfo",
         "common.MixinWorldProvider",
+        "common.MixinWorldServer",
         "common.MixinWorldSettings",
         "common.vanillaclient.ICPacketPlayer",
         "common.vanillaclient.ICPacketPlayerDigging",

src/main/resources/cubicchunks.mixins.core.vanilla.json

@@ -10,7 +10,6 @@
     "mixins": [
         "common.MixinChunk_Cubes_Vanilla_Sided",
         "common.MixinWorld_HeightLimits_Vanilla_Sided",
-        "common.MixinWorldServer",
         "common.MixinPlayerList_Vanilla_Sided"
     ],
     "client": [],