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Version: 1.21.x

Data Load Conditions

Sometimes, it is desirable to disable or enable certain features if another mod is present, or if any mod adds another type of ore, etc. For these use cases, NeoForge adds data load conditions. These were originally called recipe conditions, since recipes were the original use case for this system, but it has since been extended to other systems. This is also why some of the built-in conditions are limited to items.

Most JSON files can optionally declare a neoforge:conditions block in the root, which will be evaluated before the data file is actually loaded. Loading will continue if and only if all conditions pass, otherwise the data file will be ignored. (The exception to this rule are loot tables, which will be replaced with an empty loot table instead.)

{
  "neoforge:conditions": [
    {
      // Condition 1
    },
    {
      // Condition 2
    },
    // ...
  ],
  // The rest of the data file
}

For example, if we want to only load our file if a mod with id examplemod is present, our file would look something like this:

{
  "neoforge:conditions": [
    {
      "type": "neoforge:mod_loaded",
      "modid": "examplemod"
    }
  ],
  "type": "minecraft:crafting_shaped",
  // ...
}
note

Most vanilla files have been patched to use conditions using the ConditionalCodec wrapper. However, not all systems, especially those not using a codec, can use conditions. To find out whether a data file can use conditions, check the backing codec definition.

Built-In Conditions​

neoforge:true and neoforge:false​

These consist of no data and return the expected value.

{
  // Will always return true (or false for "neoforge:false")
  "type": "neoforge:true"
}
tip

Using the neoforge:false condition very cleanly allows disabling any data file. Simply place a file with the following contents at the needed location:

{"neoforge:conditions":[{"type":"neoforge:false"}]}

Disabling files this way will not cause log spam.

neoforge:not​

This condition accepts another condition and inverts it.

{
  // Inverts the result of the stored condition
  "type": "neoforge:not",
  "value": {
    // Another condition
  }
}

neoforge:and and neoforge:or​

These conditions accept the condition(s) being operated upon and apply the expected logic. There is no limit to the amount of accepted conditions.

{
  // ANDs the stored conditions together (or ORs for "neoforge:or")
  "type": "neoforge:and",
  "values": [
    {
      // First condition
    },
    {
      // Second condition
    }
  ]
}

neoforge:mod_loaded​

This condition returns true if a mod with the given mod id is loaded, and false otherwise.

{
  "type": "neoforge:mod_loaded",
  // Returns true if "examplemod" is loaded
  "modid": "examplemod"
}

neoforge:item_exists​

This condition returns true if an item with the given registry name has been registered, and false otherwise.

{
  "type": "neoforge:item_exists",
  // Returns true if "examplemod:example_item" has been registered
  "item": "examplemod:example_item"
}

neoforge:tag_empty​

This condition returns true if the given item tag is empty, and false otherwise.

{
  "type": "neoforge:tag_empty",
  // Returns true if "examplemod:example_tag" is an empty item tag
  "tag": "examplemod:example_tag"
}

Creating Custom Conditions​

Custom conditions can be created by implementing ICondition and its #test(IContext) method, as well as creating a map codec for it. The IContext parameter in #test has access to some parts of the game state. Currently, this only allows you to query tags from registries. Some objects with conditions may be loaded earlier than tags, in which case the context will be IContext.EMPTY and not contain any tag information at all.

For example, let's assume we want to reimplement the tag_empty condition, but for entity type tags instead of item tags, then our condition would look something like this:

// This class is basically a boiled-down copy of TagEmptyCondition, adjusted for entity types instead of items.
public record EntityTagEmptyCondition(TagKey<EntityType<?>> tag) implements ICondition {
    public static final MapCodec<EntityTagEmptyCondition> CODEC = RecordCodecBuilder.mapCodec(inst -> inst.group(
            ResourceLocation.CODEC.xmap(rl -> TagKey.create(Registries.ENTITY_TYPES, rl), TagKey::location).fieldOf("tag").forGetter(EntityTagEmptyCondition::tag)
    ).apply(inst, EntityTagEmptyCondition::new));

    @Override
    public boolean test(ICondition.IContext context) {
        return context.getTag(this.tag()).isEmpty();
    }

    @Override
    public MapCodec<? extends ICondition> codec() {
        return CODEC;
    }
}

Conditions are a registry of codecs. As such, we need to register our codec, like so:

public static final DeferredRegister<MapCodec<? extends ICondition>> CONDITION_CODECS =
        DeferredRegister.create(NeoForgeRegistries.Keys.CONDITION_CODECS, ExampleMod.MOD_ID);

public static final Supplier<MapCodec<EntityTagEmptyCondition>> ENTITY_TAG_EMPTY =
        CONDITION_CODECS.register("entity_tag_empty", () -> EntityTagEmptyCondition.CODEC);

And then, we can use our condition in some data file (assuming we registered the condition under the examplemod namespace):

{
  "neoforge:conditions": [
    {
      "type": "examplemod:entity_tag_empty",
      "tag": "minecraft:zombies"
    }
  ],
  // The rest of the data file
}

Datagen​

While any datapack JSON file can use load conditions, only a few data providers have been modified to be able to generate them. These include:

For the conditions themselves, the IConditionBuilder interface provides static helpers for each of the built-in condition types that return the corresponding IConditions.