ExampleDataGenerator.java

package com.example.examplemod.datagen;

import com.example.examplemod.ExampleMod;
import net.fabricmc.fabric.api.datagen.v1.DataGeneratorEntrypoint;
import net.fabricmc.fabric.api.datagen.v1.FabricDataGenerator;
import net.fabricmc.fabric.api.datagen.v1.provider.FabricRecipeProvider;
import net.fabricmc.fabric.api.datagen.v1.provider.FabricTagProvider;
import net.minecraft.data.recipe.RecipeExporter;
import net.minecraft.data.recipe.RecipeGenerator;
import net.minecraft.item.Items;
import net.minecraft.recipe.book.RecipeCategory;
import net.minecraft.registry.RegistryKeys;
import net.minecraft.registry.tag.ItemTags;
import net.minecraft.registry.tag.TagKey;
import net.minecraft.registry.RegistryWrapper;
import net.minecraft.util.Identifier;

import java.util.concurrent.CompletableFuture;

/**
 * Datagen entrypoint - run via the "runDatagen" Gradle task. Generates
 * recipes and item tags automatically instead of hand-writing JSON.
 * Fabric's datagen API (v1) is the current standard for 1.21.7 - 1.21.11.
 *
 * Register in fabric.mod.json -> "entrypoints" -> "fabric-datagen":
 *   ["com.example.examplemod.datagen.ExampleDataGenerator"]
 */
public class ExampleDataGenerator implements DataGeneratorEntrypoint {

    @Override
    public void onInitializeDataGenerator(FabricDataGenerator generator) {
        FabricDataGenerator.Pack pack = generator.createPack();

        pack.addProvider(ExampleRecipeProvider::new);
        pack.addProvider(ExampleItemTagProvider::new);
    }

    /** Generates a shapeless recipe: 4x example_gem -> 1 example_block. */
    private static class ExampleRecipeProvider extends FabricRecipeProvider {
        ExampleRecipeProvider(FabricDataOutput output,
                              CompletableFuture<RegistryWrapper.WrapperLookup> registriesFuture) {
            super(output, registriesFuture);
        }

        @Override
        public RecipeGenerator getRecipeGenerator(RegistryWrapper.WrapperLookup lookup, RecipeExporter exporter) {
            return new RecipeGenerator(lookup, exporter) {
                @Override
                public void generate() {
                    createShapeless(RecipeCategory.BUILDING_BLOCKS, ExampleMod.EXAMPLE_BLOCK)
                            .input(ExampleMod.EXAMPLE_GEM, 4)
                            .criterion(hasItem(ExampleMod.EXAMPLE_GEM), conditionsFromItem(ExampleMod.EXAMPLE_GEM))
                            .offerTo(exporter);
                }
            };
        }

        @Override
        public String getName() {
            return "ExampleMod Recipes";
        }
    }

    /** Adds example_gem to the c:gems tag for cross-mod compatibility. */
    private static class ExampleItemTagProvider extends FabricTagProvider.ItemTagProvider {
        ExampleItemTagProvider(FabricDataOutput output,
                               CompletableFuture<RegistryWrapper.WrapperLookup> registriesFuture) {
            super(output, registriesFuture);
        }

        @Override
        protected void configure(RegistryWrapper.WrapperLookup lookup) {
            TagKey<net.minecraft.item.Item> gemsTag = TagKey.of(RegistryKeys.ITEM, Identifier.of("c", "gems"));
            getOrCreateTagBuilder(gemsTag).add(ExampleMod.EXAMPLE_GEM);
        }
    }
}

// Note: FabricDataOutput import resolves from net.fabricmc.fabric.api.datagen.v1.FabricDataOutput