How can I make custom statistics?

[Toasterkid]

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 by Toasterkid
Adding spoiler blocks to better format the post and make it easier to scroll through.

[Toasterkid]

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 by Toasterkid

[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 by Toasterkid