Datageneration/Tags

Tags can be generated for a mod by subclassing TagsProvider and implementing #addTags. After implementation, the provider must be added to the DataGenerator.

TagsProvider

The tags provider typically generates tags via #tag.

There is another method called #getOrCreateRawBuilder, but this is typically used only in cases when two registries represent the same object but in different forms (block and items).

When #tag is called, a builder is created to which the following methods can be chained:

Method	Description
#add	Adds an object to a tag.
#addOptional	Adds an object to a tag through its name. If the object is not present, then the object will be skipped when loading.
#addTag	Adds a tag to a tag. All elements within the inner tag are now a part of the outer tag.
#addOptionalTag	Adds a tag to a tag through its name. If the tag is not present, then the tag will be skipped when loading.
#replace	When true, all previously loaded entries added to this tag from other datapacks will be discarded. If a datapack is loaded after this one, then it will still append the entries to the tag.
#remove	Removes an object or all objects within a tag from a tag. If the object is not present in the tag, nothing happens.

Java

// In some TagProvider#addTags
this.tag(EXAMPLE_TAG)
  .add(EXAMPLE_OBJECT) // Adds an object to the tag
  .addOptional(new ResourceLocation("othermod", "other_object")); // Adds an object from another mod to the tag

this.tag(EXAMPLE_TAG_2)
  .addTag(EXAMPLE_TAG) // Adds a tag to the tag
  .remove(EXAMPLE_OBJECT); // Removes an object from this tag

Important

If the mod's tags softly depends on another mod's tags (the other mod may or may not be present at runtime), the other mods' tags should be referenced using the optional methods.

Using Existing Tag Providers

Vanilla contains a few tag providers for certain registries that can be subclassed for ease of implementation.

Registry Object Type	Tag Provider
Block	BlockTagsProvider
Item	ItemTagsProvider
EntityType	EntityTypeTagsProvider
Fluid	FluidTagsProvider
GameEvent	GameEventTagsProvider
Biome	BiomeTagsProvider
FlatLevelGeneratorPreset	FlatLevelGeneratorPresetTagsProvider
WorldPreset	WorldPresetTagsProvider
Structure	StructureTagsProvider
PoiType	PoiTypeTagsProvider
BannerPattern	BannerPatternTagsProvider
CatVariant	CatVariantTagsProvider
PaintingVariant	PaintingVariantTagsProvider
Instrument	InstrumentTagsProvider

Java

public class ExampleBlockTagsProvider extends BlockTagsProvider {
    
    public ExampleBlockTagsProvider(DataGenerator gen, String modId, ExistingFileHelper efh) {
        // ...
    }

    @Override
    public void addTags() {
        // Add block tags here
    }
}

ItemTagsProvider#copy

Blocks have item representations such that they can be obtained within an inventory. As such, a number of block tags can also be applied to a similar item tag. To easily generate an item tag with the same entries as a block tag, the #copy method can be used.

Java

// In #addTags within a ItemTagsProvider subclass
this.copy(EXAMPLE_BLOCK_TAG, EXAMPLE_ITEM_TAG);

Custom Tag Providers

A custom tag provider can be created via a TagsProvider subclass which takes in the Registry to generate tags for.

Java

public RecipeTypeTagsProvider(DataGenerator gen, String modId, ExistingFileHelper efh) {
  super(gen, Registry.RECIPE_TYPE, modId, efh);
}

Forge Registry Tag Providers

If a registry is wrapped by Forge or created by a mod, a provider can be created via a ForgeRegistryTagsProvider subclass instead:

Java

public AttributeTagsProvider(DataGenerator gen, String modId, ExistingFileHelper efh) {
  super(gen, ForgeRegistries.ATTRIBUTES, modId, efh);
}