src/game/java/net/minecraft/data/registries/RegistryPatchGenerator.java

package net.minecraft.data.registries;

import com.mojang.datafixers.DataFixUtils;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
import net.minecraft.core.Cloner;
import net.minecraft.core.HolderLookup;
import net.minecraft.core.RegistryAccess;
import net.minecraft.core.RegistrySetBuilder;
import net.minecraft.core.registries.BuiltInRegistries;
import net.minecraft.core.registries.Registries;
import net.minecraft.resources.RegistryDataLoader;
import net.minecraft.world.level.biome.Biome;
import net.minecraft.world.level.levelgen.placement.PlacedFeature;

public class RegistryPatchGenerator {
    public static CompletableFuture<RegistrySetBuilder.PatchedRegistries> createLookup(
        CompletableFuture<HolderLookup.Provider> p_310881_, RegistrySetBuilder p_310262_
    ) {
        return p_310881_.thenApply(
            p_309945_ -> {
                RegistryAccess.Frozen registryaccess$frozen = RegistryAccess.fromRegistryOfRegistries(BuiltInRegistries.REGISTRY);
                Cloner.Factory cloner$factory = new Cloner.Factory();
                RegistryDataLoader.WORLDGEN_REGISTRIES.forEach(p_313050_ -> p_313050_.runWithArguments(cloner$factory::addCodec));
                RegistrySetBuilder.PatchedRegistries registrysetbuilder$patchedregistries = p_310262_.buildPatch(
                    registryaccess$frozen, p_309945_, cloner$factory
                );
                HolderLookup.Provider holderlookup$provider = registrysetbuilder$patchedregistries.full();
                Optional<? extends HolderLookup.RegistryLookup<Biome>> optional = holderlookup$provider.lookup(Registries.BIOME);
                Optional<? extends HolderLookup.RegistryLookup<PlacedFeature>> optional1 = holderlookup$provider.lookup(Registries.PLACED_FEATURE);
                if (optional.isPresent() || optional1.isPresent()) {
                    VanillaRegistries.validateThatAllBiomeFeaturesHaveBiomeFilter(
                        DataFixUtils.orElseGet(optional1, () -> p_309945_.lookupOrThrow(Registries.PLACED_FEATURE)),
                        DataFixUtils.orElseGet(optional, () -> p_309945_.lookupOrThrow(Registries.BIOME))
                    );
                }

                return registrysetbuilder$patchedregistries;
            }
        );
    }
}