Code Generation (pumpkin-codegen)

Minecraft is a massive game with thousands of block states, items, packet IDs, sound events, recipes, and biome parameters. These registries frequently change between Minecraft updates.

To maintain 100% fidelity without manually maintaining tens of thousands of error-prone constants, Pumpkin utilizes an automated code generation tool: tools/pumpkin-codegen.

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Purpose & Workflow

pumpkin-codegen parses official Minecraft server data generator reports, asset files, and version specifications, and outputs zero-cost, strongly-typed Rust files directly into crates/pumpkin-data.

The pipeline operates in three distinct stages:

1. Ingestion: Reads raw JSON assets and vanilla server reports from assets/ and assets/datapacks/.
2. Transformation: Normalizes states, calculates bitsets, processes ViaVersion remappings, and optimizes lookup tables.
3. Emission: Emits compiled Rust constants and structs into crates/pumpkin-data/src/generated.

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Generated Datasets

pumpkin-codegen generates the following components in pumpkin-data:

Category	Description	Generated Source
Packets	Serverbound and clientbound packet IDs for all protocol states across supported Minecraft versions.	packet.rs
Blocks	Block definitions, default states, state properties (facing, powered, waterlogged, etc.), and block collision boxes.	block.rs
Items	Item definitions, stack sizes, durability, data components, food properties, and equipment slots.	item.rs
Registries	Dynamic registries for biomes, dimensions, chat types, damage types, trim materials, and banner patterns.	registry.rs
Biomes & Noise	Climate parameters, noise router configurations, 3D noise settings, and surface rules.	biome.rs, noise_router.rs
Entities	Entity types, default bounding boxes, attributes, and tracked entity metadata schemas.	entity_type.rs, tracked_data.rs
Recipes & Crafting	Shaped, shapeless, smelting, blasting, smoking, and stonecutting recipes.	recipes.rs
Tags	Block tags, item tags, fluid tags, and entity type tags (e.g., #minecraft:mineable/pickaxe).	tag.rs
Enchantments & Potions	Enchantment definitions, potion effects, and brewing stand recipes.	enchantments.rs, potion.rs
Translations	Official localization keys for chat messages and item names.	translations.rs
Plugin WIT	WebAssembly Component Model WIT files defining plugin interfaces.	wit/

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Running Code Generation

To run the code generator locally:

# Navigate to the workspace root
cd Pumpkin

# Run the codegen tool
cargo run -p pumpkin-codegen

When Should You Run Codegen?

• Upgrading to a New Minecraft Version: When porting Pumpkin to a new minor or major Minecraft release.
• Adding Protocol Mappings: When adding support for an older or newer client protocol version.
• Updating WIT Definitions: When adding new functions or types to the WebAssembly plugin API.

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Data Sources

pumpkin-codegen reads data from several primary sources:

1. Minecraft Data Generator Reports: Generated by running java -DbundlerMainClass=net.minecraft.data.Main -jar server.jar --reports.
2. Minecraft Client Assets: Extracted from client .jar files for translation keys, model shapes, and sound mappings.
3. Minecraft Protocol Wiki: Cross-referenced with protocol specifications for packet IDs.