Data Generation Setup

Data Generation is used by many mods, and mojang themselves, to quickly create JSON files such as blockstates, translations and other various files that can be found in the assets/<namespace>/data folder of your project.

Why should you use Data Generation?

Although Data Generation is not really quicker for small projects with 1-2 JSON files, when you start expanding your mod and adding more blocks, biomes, dimensions etc. you might find yourself overwhelmed with JSON files.

Data Generation ensures those JSON files are kept in the correct format between game versions, and is easier to edit. It also allows you to create complex algorithms that would have been impossible to do by hand, eg: generating 100s of variants of a model due to different combinations of materials used to craft a block.

What are Data Providers?

Data Providers are where the actual data is consumed and converted into JSON, some examples include:

• FabricTranslationProvider
• FabricAdvancementProvider
• FabricCodecProvider

A full list of providers that Fabric API provides hah pun! can be found here on their GitHub repository.

Vanilla also has it's own providers, from the ModelProvider to the bare-bones DataProvider which can be used to produce custom JSON files.

Creating the Loom run configuration

Loom doesn't create the data generation run configuration by default, so you'll need to create it in your build.gradle like so:

INFO

Make sure to replace <mod-id-here> with your mod's ID!

// Add the datagen output to the jar resources.
sourceSets {
    main {
        resources {
            srcDirs += [
                    'src/main/generated'
            ]
        }
    }
}

// Create the datagen runs.
loom {
    // ...
    runs {
        datagenClient {
            client()
            name "Data Generation Client"
            vmArg "-Dfabric-api.datagen"
            vmArg "-Dfabric-api.datagen.output-dir=${file("src/main/generated")}"
            vmArg "-Dfabric-api.datagen.modid=<mod-id-here>"

            ideConfigGenerated = true
            runDir "build/datagen"
        }
    }
    // ...
}

Creating the Entrypoint

You'll need to create a class that implements the DataGeneratorEntrypoint interface, this is an entrypoint, similar to the ModInitializer and ClientModInitializer entrypoints.

It's recommended you keep this in a sub-package called datagen to stay organized.

public class MyModDatagen implements DataGeneratorEntrypoint {
    @Override
    public void onInitializeDataGenerator(FabricDataGenerator fabricDataGenerator) {
 
    }
}

As with all entrypoints, you'll need to register it in your fabric.mod.json file.

{
    // ...
    "entrypoints": {
        "fabric-datagen": [
            "com.examplemod.datagen.MyModDatagen"
        ],
    },
    // ...
}

Testing

Before continuing, it is really helpful to quickly test the Data Generation entrypoint without any providers registered, this can prevent you scratching your head in the future when you don't realize you have messed up the configuration.

To check if you have implemented Data Generation correctly into your project, run the runDatagenClient command, after it has completed, the src/main/generated folder should appear.

Registering Data Providers

To register any provider, you must first create a Pack instance using the fabricDataGenerator.createPack(); method in your entrypoint:

@Override
public void onInitializeDataGenerator(FabricDataGenerator fabricDataGenerator) {
    final FabricDataGenerator.Pack pack = dataGenerator.createPack();

    // ...
}

INFO

You should check the sidebar for a full list of providers, the MyModSoundProvider does not exist, and is used here for example purposes.

This pack can be used to register (add) providers, any providers added to the pack will be executed during data generation. You can then call the addProvider method to add providers.

final FabricDataGenerator.Pack pack = dataGenerator.createPack();

// MyModSoundProvider will be executed on data generation, and should produce a lovely sound.json file!
pack.addProvider(new MyModSoundProvider(fabricDataGenerator));