Access to registration of net.minecraft.entity.SpawnRestriction.Entry

FabricSpawnRestriction.java

package net.fabricmc.fabric.api.entity;

import net.minecraft.entity.Entity;
import net.minecraft.entity.EntityType;
import net.minecraft.entity.SpawnRestriction;
import net.minecraft.world.Heightmap;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

/**
 * Helps to set spawning settings for given entity type; see
 * {@linkplain SpawnRestriction}
 */
public class FabricSpawnRestriction<T extends Entity>
{
	@SuppressWarnings("unchecked")
	public static final List<FabricSpawnRestriction> SPAWN_RESTRICTIONS = new ArrayList()
	{
		@Override
		public boolean remove(Object o)
		{
			throw new UnsupportedOperationException();
		}

		@Override
		public Object remove(int index)
		{
			throw new UnsupportedOperationException();
		}
	};

	//Defaults
	public Heightmap.Type heightMapType = Heightmap.Type.MOTION_BLOCKING_NO_LEAVES;
	public SpawnRestriction.Location location = SpawnRestriction.Location.ON_GROUND;
	public SpawnRestriction.class_4306<T> predicate = (entityType, world, spawnType, blockPosition, random) -> true;

	public final EntityType<T> entityType;

	public FabricSpawnRestriction(EntityType<T> entityType)
	{
		this.entityType = entityType;
		Objects.requireNonNull(entityType);
	}

	public Builder<T> builder()
	{
		return new Builder<>(this);
	}

	public class Builder<E extends Entity>
	{
		private FabricSpawnRestriction<E> spawnRestriction;

		private Heightmap.Type heightMapType;
		private SpawnRestriction.Location location;
		private SpawnRestriction.class_4306<E> predicate;

		private Builder(FabricSpawnRestriction<E> fabricSpawnRestriction)
		{
			spawnRestriction = fabricSpawnRestriction;
		}

		public Builder<E> location(SpawnRestriction.Location spawnLocation)
		{
			this.location = spawnLocation;
			return this;
		}

		public Builder<E> heightMapType(Heightmap.Type heightMapType)
		{
			this.heightMapType = heightMapType;
			return this;
		}

		public Builder<E> restrictionPredicate(SpawnRestriction.class_4306<E> predicate)
		{
			this.predicate = predicate;
			return this;
		}

		/**
		 * Validates and adds the restriction
		 */
		public void build()
		{
			spawnRestriction.heightMapType = this.heightMapType;
			spawnRestriction.location = this.location;
			spawnRestriction.predicate = this.predicate;
			Objects.requireNonNull(heightMapType);
			Objects.requireNonNull(location);
			Objects.requireNonNull(predicate);
			SPAWN_RESTRICTIONS.add(spawnRestriction);
		}
	}
}

MixinSpawnRestriction.java

package net.fabricmc.fabric.mixin.builders;

import net.fabricmc.fabric.api.entity.FabricSpawnRestriction;
import net.minecraft.entity.EntityType;
import net.minecraft.entity.SpawnRestriction;
import net.minecraft.entity.mob.MobEntity;
import net.minecraft.world.Heightmap;
import org.spongepowered.asm.mixin.Mixin;
import org.spongepowered.asm.mixin.Shadow;

@Mixin(SpawnRestriction.class)
public abstract class MixinSpawnRestriction
{
	/**
	 * Represents net.minecraft.entity.SpawnRestriction#setRestrictions
	 */
	@Shadow
	private static <T extends MobEntity> void method_20637(EntityType<T> entityType, SpawnRestriction.Location spawnLocation, Heightmap.Type heightMapType, SpawnRestriction.class_4306<T> restrictionPredicate)
	{

	}

	//Registers all FabricSpawnRestriction instances
	static
	{
		FabricSpawnRestriction.SPAWN_RESTRICTIONS.forEach(fabricSpawnRestrictionBuilder -> method_20637(fabricSpawnRestrictionBuilder.entityType, fabricSpawnRestrictionBuilder.location, fabricSpawnRestrictionBuilder.heightMapType, fabricSpawnRestrictionBuilder.predicate));
	}

}

TestRestriction.java

package test;

import net.fabricmc.api.ModInitializer;
import net.fabricmc.fabric.api.entity.FabricEntityTypeBuilder;
import net.fabricmc.fabric.api.entity.FabricSpawnRestriction;
import net.minecraft.entity.*;
import net.minecraft.util.Identifier;
import net.minecraft.util.registry.Registry;
import net.minecraft.world.Heightmap;
import net.minecraft.world.biome.Biome;
import net.minecraft.world.biome.Biomes;

/**
 * Example
 */
public class TestRestriction implements ModInitializer
{
	@Override
	public void onInitialize()
	{

		EntityType<Entity> fabricEntityType = FabricEntityTypeBuilder.create(EntityCategory.MONSTER, (EntityType.EntityFactory<Entity>) TestEntity::new).size(new EntityDimensions(1, 2, false)).build();
		Registry.register(Registry.ENTITY_TYPE, new Identifier("fabric", "creeper"), fabricEntityType);
		new FabricSpawnRestriction<>(fabricEntityType).builder().heightMapType(Heightmap.Type.MOTION_BLOCKING_NO_LEAVES).location(SpawnRestriction.Location.ON_GROUND).restrictionPredicate((var1, var2, var3, var4, var5) -> true).build();
		Biomes.PLAINS.getEntitySpawnList(EntityCategory.MONSTER).add(new Biome.SpawnEntry(fabricEntityType, 100, 2, 2));
	}

}