Autogenerating data jsons in minecraft forge

AutoGeneratingDataJsonsInMinecraftForge.java

// generating data jsons from code can take advantage of the java compiler to enforce correctness,
// as well as potentially taking advantage of helper functions and classes to deal with repetitive bits of json (not demonstrated here)
// this is done by subscribing to the GatherDataEvent MOD event

// this refers to a few things from this gist:
// https://gist.github.com/Commoble/407716790fc1d3717b1a3eaac29f7423

// let's say we want to generate this loot table from code:
{
	"type": "minecraft:chest",
	"pools": 
	[
		{
			"rolls": 
			{
				"min": 3,
				"max": 10,
				"type": "minecraft:uniform"
			},
			"entries": 
			[
				{
					"type": "minecraft:loot_table",
					"name": "dungeonfist:subtables/enchanted_weapons",
					"weight": 1,
					"functions":
					[
						{
							"function": "dungeonfist:apply_functions_if_item_has_tag",
							"tag": "dungeonfist:wooden_tools",
							"functions":
							[
								{
									"function": "minecraft:set_name",
									"name": "Yep, it's wood"
								}
							]
						}
					]
				}
			]
		}
	]
}


// this event only fires when you launch runData from your IDE or wherever
// the intended use case is that you generate the data ahead-of-time and ship the mod with the generated data
// the launch config generated by the default build.gradle generates them in yourmod/src/generated/resources,
// this folder isn't read by minecraft so you'll need to move them manually or just change the launch config
// if your file path has any spaces in it, you'll need to put quotes around the path in the args as well,
// or it'll ignore everything in the path after the first space and generate them somewhere weird
// if your IDE doesn't auto-refresh when files are added externally, make sure to refresh it after you do this
@SubscribeEvent
public static void onGatherData(GatherDataEvent event)
{
	// so anything that is needed by the data gatherer must go here, such as registering custom loot functions/conditions
	// in particular, FMLCommonSetupEvent does not fire
	// if you registered any loot functions/conditions there, you'll need them here as well

	// register custom loot table functions/conditions
	LootFunctionManager.registerFunction(new ApplyFunctionsIfItemHasTag.Serializer());

	// add loot table generators
	event.getGenerator().addProvider(new DungeonLootTableProvider(event.getGenerator()));
}

////////////////
// that event needs a LootTableProvider, so we'll make one of those
////////////////

public class DungeonLootTableProvider extends LootTableProvider
{
	// if you're familiar with the top-level property "type" in loot tables
	// e.g. "type": "minecraft:chest" or "type": "minecraft:generic"
	// this determines what sorts of parameters are available to the loot table for conditions, etc
	// and when we generate loot tables, we define them with their parameter sets in this list here
	// technically, loot table builders have a method to set it in the builder
	// but this seems to be ALWAYS overridden but what we define here
	private final List<Pair<Supplier<Consumer<BiConsumer<ResourceLocation, LootTable.Builder>>>, LootParameterSet>> loot_tables =
			ImmutableList.of(Pair.of(DungeonChestLootTables::new, LootParameterSets.CHEST));
	
	public DungeonLootTableProvider(DataGenerator dataGenerator)
	{
		super(dataGenerator);
	}

	@Override
	protected List<Pair<Supplier<Consumer<BiConsumer<ResourceLocation, LootTable.Builder>>>, LootParameterSet>> getTables()
	{
		return this.loot_tables;
	}

	@Override
	public String getName()
	{
		// TODO Auto-generated method stub
		return DungeonFist.MODID + ":loot_tables";
	}

	@Override
	protected void validate(Map<ResourceLocation, LootTable> map, ValidationResults validationresults)
	{
		map.forEach((resourceLocation, lootTable) -> {
			LootTableManager.func_215302_a(validationresults, resourceLocation, lootTable, map::get);
		});
	}

}

////////////////
// We need one more thing: that DungeonChestLootTables class we referred to above
// this is where the actual loot table objects are built
// Now, when we autogenerate a loot table that pulls from other loot tables,
// we'll need those other loot tables to have been generated first
// so we'll create a few of them here
////////////////

public class DungeonChestLootTables implements Consumer<BiConsumer<ResourceLocation, LootTable.Builder>>
{
	public ResourceLocation TEST_CHEST = new ResourceLocation(DungeonFist.MODID, "chests/test");
	
	// subtable locations
	public ResourceLocation ENCHANTED_WEAPONS = new ResourceLocation(DungeonFist.MODID, "subtables/enchanted_weapons");
	public ResourceLocation WEAPONS = new ResourceLocation(DungeonFist.MODID, "subtables/weapons");
	
	public ResourceLocation WOODEN_TOOLS_TAG = new ResourceLocation(DungeonFist.MODID, "wooden_tools");
	
	@Override
	public void accept(BiConsumer<ResourceLocation, Builder> builderConsumer)
	{
		builderConsumer.accept(
			this.WEAPONS,
			LootTable.builder().addLootPool(
				LootPool.builder().rolls(ConstantRange.of(1))
				.addEntry(ItemLootEntry.builder(Items.IRON_SWORD).weight(40))
				.addEntry(ItemLootEntry.builder(Items.IRON_AXE).weight(40))
				.addEntry(ItemLootEntry.builder(Items.BOW).weight(11))
				.addEntry(ItemLootEntry.builder(Items.GOLDEN_SWORD).weight(1))
				.addEntry(ItemLootEntry.builder(Items.GOLDEN_AXE).weight(1))
				.addEntry(ItemLootEntry.builder(Items.WOODEN_SWORD).weight(40))
				.addEntry(ItemLootEntry.builder(Items.WOODEN_AXE).weight(1))
				.addEntry(ItemLootEntry.builder(Items.DIAMOND_SWORD).weight(1))
				.addEntry(ItemLootEntry.builder(Items.DIAMOND_AXE).weight(1))
				.addEntry(ItemLootEntry.builder(Items.TRIDENT).weight(1))
			)
		);
		
		builderConsumer.accept(
			this.ENCHANTED_WEAPONS,
			LootTable.builder().addLootPool(
				LootPool.builder().rolls(ConstantRange.of(1)).addEntry(
					TableLootEntry.builder(this.WEAPONS).weight(1).acceptFunction(
						// unmapped function names: This gets the builder for EnchantWithLevels,
						// sets the random level range to between 1 and 5, and enables treasure enchantments
						EnchantWithLevels.func_215895_a(RandomValueRange.func_215837_a(1F, 5F)).func_216059_e()
					)
				).addEntry(
					TableLootEntry.builder(this.WEAPONS).weight(1).acceptFunction(
						EnchantWithLevels.func_215895_a(RandomValueRange.func_215837_a(10F, 20F)).func_216059_e()
					)
				)
			)
		);
		
		builderConsumer.accept(
			this.TEST_CHEST,
			LootTable.builder().addLootPool(
				LootPool.builder().rolls(RandomValueRange.func_215837_a(3F, 10F)).addEntry(
					TableLootEntry.builder(this.ENCHANTED_WEAPONS).acceptFunction(
						ApplyFunctionsIfItemHasTag.getBuilder(
							this.WOODEN_TOOLS_TAG, 
							ApplyFunctionsIfItemHasTag.getSetNameBuilder(new StringTextComponent("Yep, it's wood"), null).build()
						)
					)
				)
			)
		);
	}
}