I am attempting to create a mod that adds custom statistics to Minecraft.

I've had some help from LexManos on the Discord server, but posting a lot of what I posted in the #mod-dev-support-1.20 channel here to have a more permanent spot for discussion.

 

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Minecraft creates their stats like this:

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public class Stats {
   public static final StatType<Block> BLOCK_MINED = makeRegistryStatType("mined", BuiltInRegistries.BLOCK);
   public static final StatType<Item> ITEM_CRAFTED = makeRegistryStatType("crafted", BuiltInRegistries.ITEM);
   public static final StatType<EntityType<?>> ENTITY_KILLED = makeRegistryStatType("killed", BuiltInRegistries.ENTITY_TYPE);
   public static final StatType<ResourceLocation> CUSTOM = makeRegistryStatType("custom", BuiltInRegistries.CUSTOM_STAT);
   public static final ResourceLocation LEAVE_GAME = makeCustomStat("leave_game", StatFormatter.DEFAULT);
   public static final ResourceLocation PLAY_TIME = makeCustomStat("play_time", StatFormatter.TIME);
  
   private static ResourceLocation makeCustomStat(String p_13008_, StatFormatter p_13009_) {
      ResourceLocation resourcelocation = new ResourceLocation(p_13008_);
      Registry.register(BuiltInRegistries.CUSTOM_STAT, p_13008_, resourcelocation);
      CUSTOM.get(resourcelocation, p_13009_);
      return resourcelocation;
   }

   private static <T> StatType<T> makeRegistryStatType(String p_13011_, Registry<T> p_13012_) {
      Component component = Component.translatable("stat_type.minecraft." + p_13011_);
      return Registry.register(BuiltInRegistries.STAT_TYPE, p_13011_, new StatType<>(p_13012_, component));
   }
}

and some of the registries in the code above are located in BuiltInRegistries.java like this:

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/**
 * @deprecated Forge: Use {@link net.minecraftforge.registries.ForgeRegistries#STAT_TYPES} instead.
 */
@Deprecated
public static final Registry<StatType<?>> STAT_TYPE = forge(Registries.STAT_TYPE, (p_259967_) -> {
    return Stats.ITEM_USED;
});

public static final Registry<ResourceLocation> CUSTOM_STAT = registerSimple(Registries.CUSTOM_STAT, (p_259833_) -> {
    return Stats.JUMP;
});

and the ForgeRegistries#STAT_TYPES looks like this:

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public static final IForgeRegistry<StatType<?>> STAT_TYPES = active(Keys.STAT_TYPES);

So, attempting to follow that and the forge documentation on registries I arrived at this:

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public class SampleModStatisticsRegistry {

    public static final DeferredRegister<StatType<?>> STATISTICS = DeferredRegister.create(ForgeRegistries.STAT_TYPES, SampleMod.MODID);

    public static final RegistryObject<StatType<?>> FIREWORK_BOOSTS_USED = STATISTICS.register("firework_boosts_used",
            () -> makeRegistryStatType("firework_boosts_used", BuiltInRegistries.CUSTOM_STAT));

    // code stolen from Minecraft's Stats file
    public static <T> StatType<T> makeRegistryStatType(String p_13011_, Registry<T> p_13012_) {
        Component component = Component.translatable("stat_type.minecraft." + p_13011_);
        return Registry.register(BuiltInRegistries.STAT_TYPE, p_13011_, new StatType<>(p_13012_, component));
    }
}

Clearly, registering a stat twice in a row is the wrong way to do it, but the makeRegistryStatType function was used as it does give the correct return type for the code I had come up with so far.

 

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At this point the game crashes upon trying to use Player#awardStat, because of a NPE that occurs in Stat#locationToKey.

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java.lang.NullPointerException: Cannot invoke "net.minecraft.resources.ResourceLocation.toString()" because "p_12866_" is null
	at net.minecraft.stats.Stat.locationToKey(Stat.java:26) ~[forge-1.20.2-48.1.0_mapped_official_1.20.2-recomp.jar%23199!/:?] {re:classloading}
	at net.minecraft.stats.Stat.buildName(Stat.java:22) ~[forge-1.20.2-48.1.0_mapped_official_1.20.2-recomp.jar%23199!/:?] {re:classloading}
	at net.minecraft.stats.Stat.<init>(Stat.java:15) ~[forge-1.20.2-48.1.0_mapped_official_1.20.2-recomp.jar%23199!/:?] {re:classloading}
	at net.minecraft.stats.StatType.lambda$get$0(StatType.java:25) ~[forge-1.20.2-48.1.0_mapped_official_1.20.2-recomp.jar%23199!/:?] {re:classloading}
	at java.util.Map.computeIfAbsent(Map.java:1054) ~[?:?] {re:mixin}
	at net.minecraft.stats.StatType.get(StatType.java:24) ~[forge-1.20.2-48.1.0_mapped_official_1.20.2-recomp.jar%23199!/:?] {re:classloading}
	at net.minecraft.stats.StatType.get(StatType.java:38) ~[forge-1.20.2-48.1.0_mapped_official_1.20.2-recomp.jar%23199!/:?] {re:classloading}
	at net.minecraft.world.entity.player.Player.awardStat(Player.java:1364) ~[forge-1.20.2-48.1.0_mapped_official_1.20.2-recomp.jar%23199!/:?] {re:classloading,pl:accesstransformer:B}

Which happens in the 2nd Stat#locationToKey in the Stat#buildName function.

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public static <T> String buildName(StatType<T> p_12863_, T p_12864_) {
    return locationToKey(BuiltInRegistries.STAT_TYPE.getKey(p_12863_)) + ":" + locationToKey(p_12863_.getRegistry().getKey(p_12864_));
}

The .getRegistry returns the this.registry class variable with a value of {MappedRegistry@#####} "Registry[ResourceKey[minecraft:root / minecraft:custom_stat] (Stable)]"

The value passed into .getKey is "samplemod:fireworks_boosts_used" but the reference found is null.

So Lex's conclusion was that "[I'm] passing in null because the registry doesnt have an entry for your custom stat instance. So.. register your custom stat instance in that registry."

 

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So I suppose at this point my questions are

1. How can I create a supplier that returns a Supplier<? extends StatType<?>> to replace the () -> makeRegistryStatType("firework_boosts_used", BuiltInRegistries.CUSTOM_STAT) line of code.

2. Is my registry entry public static final RegistryObject<StatType<?>> FIREWORK_BOOSTS_USED the correct type?

3. Do I need to do anything additional, like create my own StatType<> or my own Stat<> ?

Edited October 5, 20241 yr by Toasterkid
Adding spoiler blocks to better format the post and make it easier to scroll through.

At an attempt at answering my first question I thought I might be able to change the code to this

public class SampleModStatisticsRegistry {

    public static final DeferredRegister<StatType<?>> STATISTICS = DeferredRegister.create(ForgeRegistries.STAT_TYPES, SampleMod.MODID);

    public static final RegistryObject<StatType<?>> FIREWORK_BOOSTS_USED = STATISTICS.register("firework_boosts_used", 
            () -> new StatType<>(ForgeRegistries.STAT_TYPES, Component.literal("firework_boosts")));
  
}

or to this

public class SampleModStatisticsRegistry {

    public static final DeferredRegister<StatType<?>> STATISTICS = DeferredRegister.create(ForgeRegistries.STAT_TYPES, SampleMod.MODID);

    public static final RegistryObject<StatType<?>> FIREWORK_BOOSTS_USED = STATISTICS.register("firework_boosts_used",
            () -> new StatType<>(BuiltInRegistries.STAT_TYPE, Component.literal("firework_boosts")));
  
}

but for the first code snippet the StatType constructor requires a Registry not an IForgeRegistry

and for the second code snippet we run into the same NPE issue from above.

Edited October 5, 20241 yr by Toasterkid

Also doubting if my usage of awardStat is correct.

It just looks like this right now:

player.awardStat(SampleModRegistry.FIREWORK_BOOSTS_USED.getId());

but there are places vanilla Minecraft uses the function like this:

.awardStat(Stats.CUSTOM.get(Stats.DAMAGE_BLOCKED_BY_SHIELD)

Edited October 5, 20241 yr by Toasterkid