Datagenerating worldgen registry jsons in forge for minecraft 1.18.2

BiomeCheeserDatagen.java

package biomecheeser;

import java.io.IOException;
import java.nio.file.Path;
import java.util.List;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.mojang.serialization.Codec;
import com.mojang.serialization.JsonOps;

import commoble.biomecheeser.BiomeCheeser;
import net.minecraft.core.Registry;
import net.minecraft.core.RegistryAccess;
import net.minecraft.data.DataGenerator;
import net.minecraft.data.DataProvider;
import net.minecraft.data.HashCache;
import net.minecraft.data.worldgen.placement.PlacementUtils;
import net.minecraft.resources.RegistryOps;
import net.minecraft.resources.ResourceKey;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.server.packs.PackType;
import net.minecraft.world.level.block.Blocks;
import net.minecraft.world.level.levelgen.feature.ConfiguredFeature;
import net.minecraft.world.level.levelgen.feature.Feature;
import net.minecraft.world.level.levelgen.feature.configurations.BlockPileConfiguration;
import net.minecraft.world.level.levelgen.feature.stateproviders.BlockStateProvider;
import net.minecraft.world.level.levelgen.placement.InSquarePlacement;
import net.minecraft.world.level.levelgen.placement.PlacedFeature;
import net.minecraftforge.eventbus.api.SubscribeEvent;
import net.minecraftforge.fml.common.Mod.EventBusSubscriber;
import net.minecraftforge.fml.common.Mod.EventBusSubscriber.Bus;
import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
import net.minecraftforge.forge.event.lifecycle.GatherDataEvent;
import net.minecraftforge.registries.DeferredRegister;
import net.minecraftforge.registries.RegistryObject;

/* Example of generating data for jsons of worldgen registry objects */
/* 1) use deferred registers and registry objects to register BuiltinRegistries objects such as configured/placed features
 * 2) create the RegistryAccess and RegistryOps
 * 3) get the relevant registry from the registryaccess
 * 4) get the object from that registry
 * 5) use the RegistryOps and direct codec to serialize it
 */
@EventBusSubscriber(modid=BiomeCheeser.MODID, bus=Bus.MOD)
public class BiomeCheeserDatagen
{
	private static final Logger LOGGER = LogManager.getLogger();
	
	// 1) use deferred registers and registry objects to register BuiltinRegistries objects such as configured/placed features
	// (even if you don't use them in java, this is needed for datagen)
	public static <T> DeferredRegister<T> makeVanillaDeferredRegister(ResourceKey<Registry<T>> registryKey)
	{
		DeferredRegister<T> register = DeferredRegister.create(registryKey, BiomeCheeser.MODID);
		register.register(FMLJavaModLoadingContext.get().getModEventBus());
		return register;
	}
	private static final DeferredRegister<ConfiguredFeature<?,?>> CONFIGURED_FEATURES = makeVanillaDeferredRegister(Registry.CONFIGURED_FEATURE_REGISTRY);
	private static final DeferredRegister<PlacedFeature> PLACED_FEATURES = makeVanillaDeferredRegister(Registry.PLACED_FEATURE_REGISTRY);
	
	public static final String TNT_PILE_NAME = "tnt_pile";
	public static final ResourceKey<ConfiguredFeature<?,?>> CONFIGURED_TNT_PILE_KEY = ResourceKey.create(Registry.CONFIGURED_FEATURE_REGISTRY, new ResourceLocation(BiomeCheeser.MODID, TNT_PILE_NAME));
	private static final RegistryObject<ConfiguredFeature<?,?>> CONFIGURED_TNT_PILE =
		CONFIGURED_FEATURES.register(TNT_PILE_NAME,
			() -> new ConfiguredFeature<>(Feature.BLOCK_PILE,
				new BlockPileConfiguration(BlockStateProvider.simple(Blocks.TNT))));
	public static final ResourceKey<PlacedFeature> PLACED_TNT_PILE_KEY = ResourceKey.create(Registry.PLACED_FEATURE_REGISTRY, new ResourceLocation(BiomeCheeser.MODID, TNT_PILE_NAME));
	private static final RegistryObject<PlacedFeature> PLACED_TNT_PILE =
		PLACED_FEATURES.register(TNT_PILE_NAME, 
			() -> new PlacedFeature(CONFIGURED_TNT_PILE.getHolder().get(),
				List.of(InSquarePlacement.spread(), PlacementUtils.HEIGHTMAP)));
	
	@SubscribeEvent
	public static void onGatherData(GatherDataEvent event)
	{
		DataGenerator generator = event.getGenerator();
		Path outputFolder = generator.getOutputFolder();
		// 2) create the RegistryAccess and RegistryOps
		RegistryAccess registries = RegistryAccess.builtinCopy();
		RegistryOps<JsonElement> ops = RegistryOps.create(JsonOps.INSTANCE, registries);
		Gson gson = new GsonBuilder()
			.setPrettyPrinting()
			.create();
		// we use the helper method below to provide a list of resource keys of one registry type to make jsons for
		generator.addProvider(
			makeBuiltinRegistryProvider(BiomeCheeser.MODID, outputFolder, gson, ops, registries, Registry.CONFIGURED_FEATURE_REGISTRY, ConfiguredFeature.DIRECT_CODEC,
				CONFIGURED_TNT_PILE_KEY));
		generator.addProvider(
			makeBuiltinRegistryProvider(BiomeCheeser.MODID, outputFolder, gson, ops, registries, Registry.PLACED_FEATURE_REGISTRY, PlacedFeature.DIRECT_CODEC,
				PLACED_TNT_PILE_KEY));
	}
	
	/* Helper method that serializes many objects of the same registry type for us (note the vararg)*/
	@SafeVarargs
	private static <T> DataProvider makeBuiltinRegistryProvider(String modid, Path outputFolder, Gson gson, RegistryOps<JsonElement> ops, RegistryAccess registries, ResourceKey<Registry<T>> registryKey, Codec<T> codec, ResourceKey<T>... keys)
	{
		return new DataProvider()
		{
			@Override
			public void run(HashCache cache) throws IOException
			{
				// 3) get the relevant registry from the registryaccess
				// we must retrieve objects from registryaccess and not via our RegistryObject
				// (as this is where RegistryOps looks up the id names of things to write out)
				Registry<T> registry = registries.registryOrThrow(registryKey);
				for (ResourceKey<T> key : keys)
				{
					ResourceLocation id = key.location();
					Path path = outputFolder.resolve(String.join("/", PackType.SERVER_DATA.getDirectory(), id.getNamespace(), registryKey.location().getPath(), id.getPath()+".json"));
					// 4) get the object from that registry
					T t = registry.getOrThrow(key);
					// 5) use the RegistryOps and direct codec to serialize it
					// (as of 1.18.2 the indirect codec is no longer the correct codec for datagen)
					codec.encodeStart(ops, t)
						.resultOrPartial(msg -> LOGGER.error("Failed to encode {}: {}", path, msg))
						.ifPresent(json -> {
							try
							{
								DataProvider.save(gson, cache, json, path);
							}
							catch (IOException e) // we're inside this ifpresent so the throws can't deal with this
							{
								e.printStackTrace();
							}
						});
				}
			}

			@Override
			public String getName()
			{
				return modid + " " + registryKey.location().toString();
			}
		};
	}
}

configured_tnt_pile.json

//data/biomecheeser/worldgen/configured_feature/tnt_pile.json
{
  "config": {
    "state_provider": {
      "state": {
        "Properties": {
          "unstable": "false"
        },
        "Name": "minecraft:tnt"
      },
      "type": "minecraft:simple_state_provider"
    }
  },
  "type": "minecraft:block_pile"
}

placed_tnt_pile.json

//data/biomecheeser/worldgen/placed_feature/tnt_pile.json
{
  "feature": "biomecheeser:tnt_pile",
  "placement": [
    {
      "type": "minecraft:in_square"
    },
    {
      "heightmap": "MOTION_BLOCKING",
      "type": "minecraft:heightmap"
    }
  ]
}