handle IEntityAdditionalSpawnData at the right time

modules/entity/src/main/java/io/github/fabricators_of_create/porting_lib/entity/client/PortingLibEntityClient.java

@@ -1,29 +1,30 @@
 package io.github.fabricators_of_create.porting_lib.entity.client;
 
+import java.util.Objects;
+
 import io.github.fabricators_of_create.porting_lib.core.PortingLib;
 import io.github.fabricators_of_create.porting_lib.entity.IEntityAdditionalSpawnData;
 import io.github.fabricators_of_create.porting_lib.entity.MultiPartEntity;
 import io.github.fabricators_of_create.porting_lib.entity.PartEntity;
+import io.github.fabricators_of_create.porting_lib.entity.mixin.common.BlockableEventLoopAccessor;
 import net.fabricmc.api.ClientModInitializer;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 import net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientEntityEvents;
 import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
-import net.fabricmc.fabric.api.networking.v1.PacketByteBufs;
 import net.fabricmc.fabric.api.networking.v1.PacketSender;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.multiplayer.ClientPacketListener;
 import net.minecraft.network.FriendlyByteBuf;
-import net.minecraft.network.protocol.game.ClientboundAddEntityPacket;
 import net.minecraft.world.entity.Entity;
 
 public class PortingLibEntityClient implements ClientModInitializer {
 	@Environment(EnvType.CLIENT)
 	private static void handlePacketReceived(Minecraft client, ClientPacketListener handler, FriendlyByteBuf buf, PacketSender responseSender) {
 		int entityId = buf.readVarInt();
 		buf.retain(); // save for execute
-		client.execute(() -> {
-			Entity entity = client.level.getEntity(entityId);
+		execute(client, () -> {
+			Entity entity = Objects.requireNonNull(client.level).getEntity(entityId);
 			if (entity instanceof IEntityAdditionalSpawnData extra) {
 				extra.readSpawnData(buf);
 			} else {
@@ -32,6 +33,19 @@ private static void handlePacketReceived(Minecraft client, ClientPacketListener
 			buf.release();
 		});
 	}
+
+	private static void execute(Minecraft mc, Runnable task) {
+		// sometimes MC will defer a task even if already on the right thread.
+		// Forge avoids this when calling enqueueWork.
+		// We need to replicate this behavior for proper packet ordering.
+		if (mc.isSameThread()) {
+			task.run();
+		} else {
+			// Forge also bypasses public methods
+			((BlockableEventLoopAccessor) mc).callSubmitAsync(task);
+		}
+	}
+
 	@Override
 	public void onInitializeClient() {
 		ClientPlayNetworking.registerGlobalReceiver(IEntityAdditionalSpawnData.EXTRA_DATA_PACKET, PortingLibEntityClient::handlePacketReceived);

modules/entity/src/main/java/io/github/fabricators_of_create/porting_lib/entity/mixin/common/BlockableEventLoopAccessor.java

@@ -0,0 +1,14 @@
+package io.github.fabricators_of_create.porting_lib.entity.mixin.common;
+
+import java.util.concurrent.CompletableFuture;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Invoker;
+
+import net.minecraft.util.thread.BlockableEventLoop;
+
+@Mixin(BlockableEventLoop.class)
+public interface BlockableEventLoopAccessor {
+	@Invoker
+	CompletableFuture<Void> callSubmitAsync(Runnable task);
+}

modules/entity/src/main/resources/porting_lib_entity.mixins.json

@@ -8,6 +8,7 @@
     "common.AbstractHorseMixin",
     "common.AbstractHurtingProjectileMixin",
     "common.AbstractMinecartMixin",
+    "common.BlockableEventLoopAccessor",
     "common.BlockBehaviourMixin",
     "common.BundlePacketMixin",
     "common.CatSpawnerMixin",