Porting to Newer Minecraft Versions

Upgrading Pumpkin to support a newer Minecraft release—whether a minor patch (e.g., 1.21.4 to 1.21.5) or a major update (e.g., 1.21 to 26.1/26.2)—is a structured, multi-step process.

IMPORTANT

The Extractor mod must be ported first! Pumpkin cannot be ported in isolation. The primary source for Pumpkin's assets (blocks.json, items.json, entities.json, packets.json, tracked_data.json, synced_registries.json, etc.) is our dedicated Fabric mod: Pumpkin-MC/Extractor. You must first port and run the Extractor on the target Minecraft version before running pumpkin-codegen or updating server crates.

Porting Lifecycle at a Glance

Stage	Responsibility	Primary Crates / Tools
1. Port Extractor	Extract vanilla block states, entities, items, packets, and registries	`Pumpkin-MC/Extractor` (Fabric mod)
2. Update Datapacks	Ingest new data packs, tags, recipes, and Bedrock mappings	`assets/datapacks/<ver>`, `assets/bedrock`
3. Version Declarations	Register protocol version and ViaVersion/ViaBackwards remap nodes	`pumpkin-util`, `tools/pumpkin-codegen`
4. Code Generation	Regenerate zero-cost Rust data tables and registries	`pumpkin-codegen` -> `pumpkin-data`
5. Compiler Fixes	Update packet layouts, codecs, and data components	`pumpkin-protocol`, `pumpkin-inventory`
6. Gameplay Logic	Implement new block behaviors, item mechanics, and mob AI	`crates/pumpkin/src/block`, `item`, `entity`
7. Multi-Version QA	Validate backward compatibility, test suites, and client joins	`cargo test`, `pumpkin-gametest`

Phase 1: Port the Extractor Mod First (`Pumpkin-MC/Extractor`)

The Extractor is a Kotlin-based Fabric mod that boots an actual Minecraft client or server instance to introspect live game registries and extract data into the exact JSON formats Pumpkin expects.

1. Clone or Update the Extractor Repository

bash

git clone https://github.com/Pumpkin-MC/Extractor
cd Extractor

2. Update `gradle.properties`

Bump the dependency versions to match the target Minecraft version, Yarn mappings, and Fabric ecosystem:

properties

minecraft_version=26.2
yarn_mappings=26.2+build.1:v2
loader_version=0.16.10
fabric_version=0.115.0+26.2

3. Resolve Extractor Compilation Errors

Minecraft and Fabric internal APIs often change between releases. Check and fix any broken extractors in src/main/kotlin/de/snowii/extractor/extractors/:

Blocks.kt: Extracts block states, hardness, resistance, luminance, and collision box offsets.
Items.kt: Extracts item IDs, max stack sizes, and default components.
Entities.kt: Extracts entity IDs, dimensions (width, height), and eye heights.
Packets.kt: Extracts packet IDs for handshake, status, login, configuration, and play states.
SyncedRegistries.kt: Extracts dynamic registries synchronized to clients.
TrackedData.kt: Extracts entity tracked data indices and serializers.
MultiNoise.kt & Biome.kt: Extracts world generation biome trees and noise parameters.

4. Run the Extractor

Execute the server runner (or client runner for translation/screen dumps):

bash

./gradlew runServer

Once the extraction finishes, all dumped JSON files will be located in run/pumpkin_extractor_output/.

5. Replace the Old Asset Files in Pumpkin

Copy the newly generated JSON files from run/pumpkin_extractor_output/ and use them to replace the old asset files in Pumpkin:

Replace the core game assets in Pumpkin/assets/ (blocks.json, items.json, entities.json, packets.json, properties.json, synced_registries.json, tracked_data.json, en_us.json, etc.).
Replace the world generation test files in Pumpkin/crates/pumpkin-world/assets/.

Phase 2: Update Assets & Datapacks

Once the raw extractor assets are in place, update the versioned datapacks and supplemental files in Pumpkin:

1. Add the Versioned Datapack

Extract the internal vanilla data pack from the new Minecraft server JAR and place it under assets/datapacks/<version>/:

assets/datapacks/<version>/
└── data/
    ├── minecraft/
    │   ├── advancement/
    │   ├── chat_type/
    │   ├── damage_type/
    │   ├── dimension_type/
    │   ├── enchantment/
    │   ├── item_modifier/
    │   ├── loot_table/
    │   ├── recipe/
    │   ├── tags/
    │   └── worldgen/
    └── c/
        └── tags/ (Conventional / Common Tags)

2. Update Versioned Assets

Update or generate the corresponding versioned metadata files:

assets/registry/<version>_synced_registries.json: Dynamic registries streamed to the client during the Configuration network state.
assets/tags/<version>_tags.json: Tag collections.
assets/tracked_data/<version>_tracked_data.json: Entity metadata indices.

3. Update Bedrock Mappings

If porting Bedrock Edition support simultaneously, update the files in assets/bedrock/ using the latest mappings from GeyserMC and Bedrock Dedicated Server (BDS).

4. Decompile Sources for Reverse Engineering (Optional but Recommended)

For complex changes—such as worldgen noise router formulas and custom block collision shapes—decompile the matching vanilla JAR into minecraft-sources-<version>/ (using Vineflower or Fabric Loom with official Mojang mappings) for reference.

Phase 3: Register Version Constants & ViaVersion Mappings

Pumpkin supports multi-version clients through automated protocol remapping powered by ViaBackwards / ViaRewind mapping tables.

1. Declare Version in `pumpkin-util`

Open crates/pumpkin-util/src/version.rs and add the new version to JavaMinecraftVersion:

rust

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub enum JavaMinecraftVersion {
    // ... existing versions ...
    V_1_21_4,
    V_1_21_11,
    V_26_2, // New target version
}

impl JavaMinecraftVersion {
    pub const fn protocol_version(&self) -> i32 {
        match self {
            // ...
            Self::V_26_2 => 770, // Protocol version number
        }
    }

    pub const fn version_name(&self) -> &'static str {
        match self {
            // ...
            Self::V_26_2 => "26.2",
        }
    }
}

2. Declare Version in `pumpkin-codegen`

Open tools/pumpkin-codegen/src/version.rs and add the identical enum variant to the codegen AST.

3. Add ViaVersion / ViaBackwards Mappings

To enable clients on older versions to connect to the updated server (e.g., a 1.21.4 client connecting to a 26.2 server):

Obtain the NBT mapping file from the ViaBackwards repository: mappings-<new_version>to<previous_version>.nbt
Save it to: assets/viabackwards/data/mappings-<new_version>to<previous_version>.nbt
In tools/pumpkin-codegen/src/remap/mod.rs, link the new node into the remap_nodes! macro:

rust

let node_26_2 = $crate::remap::MappingNode {
    version: $crate::version::JavaMinecraftVersion::V_26_2,
    value: "../../assets/viabackwards/data/mappings-26.2to26.1.nbt",
    child: Some(&node_26_1),
};
$remapper.process(&node_26_2)

Check tools/pumpkin-codegen/src/remap/ to ensure specific remap builders (block_state.rs, item_id.rs, entity_id.rs, sound_id.rs, argument_type.rs) correctly process any new remapping structures introduced by ViaVersion.

Phase 4: Run Code Generation (`pumpkin-codegen`)

With all extractor assets, datapacks, and mapping nodes in place, execute the codegen tool from the workspace root:

bash

cargo run -p pumpkin-codegen

What Gets Regenerated?

pumpkin-codegen generates zero-cost Rust data tables into crates/pumpkin-data/src/generated/:

block.rs: All block IDs, properties, state masks, and collision shapes.
item.rs: Items, default components, and tool tiers.
entity_type.rs & tracked_data.rs: Entity type IDs, default bounding boxes, and metadata serializers.
packet.rs: Serverbound and clientbound packet ID constants across protocol states.
recipes.rs: All crafting, cooking, and stonecutting recipes parsed from the new datapack.
tag.rs: Tag lookups (#minecraft:mineable/axe, #c:iron_ingots).
remap/*.rs: State remap lookup tables (block_state_remap.rs, item_id_remap.rs, entity_id_remap.rs, sound_id_remap.rs).

Phase 5: Resolve Workspace Compilation Errors

After regenerating pumpkin-data, the Rust compiler will flag breaking changes across the workspace. Run:

bash

cargo check --workspace

Common Compiler Breakages & Fixes:

1. Packet ID & Layout Changes (`pumpkin-protocol`)

Mojang frequently adds, moves, or alters packet IDs and payloads:

Update pumpkin-protocol/src/java/client/ and pumpkin-protocol/src/java/server/.
Inspect packets like LoginSuccess, PlayLogin, Respawn, and PlayerSpawnData for newly added fields (e.g., new game mode flags, dimension attributes, or teleportation IDs).
For Bedrock Edition, check StartGame, NetworkItem, and container transaction packets in pumpkin-protocol/src/bedrock/.

2. Data Component Changes

If items switched from older NBT structures to new Data Components (or if components were renamed/restructured):

Update crates/pumpkin-data/src/data_component.rs.
Update serialization and deserialization in pumpkin-inventory.

3. Registry Synchronization

During the Configuration phase, servers send dynamic registry contents to Java clients. If new registries were added to vanilla Minecraft (e.g., trim materials, banner patterns, instrument sounds):

Verify crates/pumpkin-data/src/generated/registry.rs.
Ensure pumpkin/src/net/java/config.rs streams all required registry codecs to the client.

Phase 6: Implement Logic for New Blocks, Items & Entities

Once the server compiles, any newly introduced gameplay content must be implemented.

1. New Blocks

Locate new block identifiers in pumpkin-data::Block.

Create a behavior module under crates/pumpkin/src/block/blocks/<block_name>.rs implementing BlockBehaviour:

rust

pub struct NewBlockBehaviour;

impl BlockBehaviour for NewBlockBehaviour {
    fn on_use(&self, block: &Block, player: &Arc<Player>, location: BlockPos, world: &Arc<World>) {
        // Interaction logic
    }
}

2. New Items

Locate new item identifiers in pumpkin-data::Item.
If the item has unique right-click or use behavior (e.g., weapons, projectiles, instruments), create an item behavior in crates/pumpkin/src/item/items/<item_name>.rs implementing ItemBehaviour.
If the item places entities (e.g., spawn eggs, boats, minecarts), configure entity spawning logic in pumpkin/src/item/items/spawn_egg.rs.
Register the behavior in crates/pumpkin/src/item/mod.rs.

3. New Entities

Check pumpkin-data::entity_type::EntityType for new entity IDs.
Create an entity struct in crates/pumpkin/src/entity/mob/ or living/ extending LivingEntity.
Implement TrackedData fields to match vanilla client expectations (e.g., poses, animations, glowing states).
Assign AI goals and navigation tasks using the Mob AI & Goals system.
Add spawn packet construction in crates/pumpkin/src/entity/spawning.rs.

Phase 7: Multi-Version & ViaVersion Verification

Ensure that older clients can still connect seamlessly:

Verify Generated Remap Tables: Check crates/pumpkin-data/src/generated/block_state_remap.rs and item_id_remap.rs. Ensure that novel block states fall back gracefully to compatible equivalents on older client versions (e.g., new wood variants mapping to oak or spruce).
Packet Translation: Verify that packet writers in pumpkin-protocol apply remap functions when serializing data for a connection whose negotiated protocol_version is older than the server's native version.

Phase 8: Testing & Verification Checklist

Before opening a Pull Request for a version port, complete the following QA checklist:

Automated Tests:
bash
```
cargo test --workspace
```
Game Test Suite:
bash
```
cargo test -p pumpkin-gametest
```

Strict Linter Rules:

bash

cargo clippy --workspace --all-targets -- -D warnings

Spellcheck:
bash
```
typos
```
In-Game Java Client Test:
- Connect with the native new Minecraft client version.
- Test login, world loading, chunk generation, and player movement.
- Place and break new blocks; verify collision boxes and redstone reactivity.
- Use and equip new items; test attack speed, durability, and animations.
- Spawn and fight new entities; test animations, hurt sounds, and drops.
In-Game Older Version Client Test:
- Connect with an older supported client version (e.g., 1.21.x).
- Verify that blocks, items, and entities translate without causing client crashes or desyncs.
In-Game Bedrock Client Test:
- Verify that Bedrock clients can authenticate, join, load world chunks, and view custom items.

Java Edition

Bedrock Edition

プロキシ転送

コマンド

Porting to Newer Minecraft Versions ​

Porting Lifecycle at a Glance ​

Phase 1: Port the Extractor Mod First (Pumpkin-MC/Extractor) ​

1. Clone or Update the Extractor Repository ​

2. Update gradle.properties ​

3. Resolve Extractor Compilation Errors ​

4. Run the Extractor ​

5. Replace the Old Asset Files in Pumpkin ​

Phase 2: Update Assets & Datapacks ​

1. Add the Versioned Datapack ​

2. Update Versioned Assets ​

3. Update Bedrock Mappings ​

4. Decompile Sources for Reverse Engineering (Optional but Recommended) ​

Phase 3: Register Version Constants & ViaVersion Mappings ​

1. Declare Version in pumpkin-util ​

2. Declare Version in pumpkin-codegen ​

3. Add ViaVersion / ViaBackwards Mappings ​

Phase 4: Run Code Generation (pumpkin-codegen) ​

What Gets Regenerated? ​

Phase 5: Resolve Workspace Compilation Errors ​

Common Compiler Breakages & Fixes: ​

1. Packet ID & Layout Changes (pumpkin-protocol) ​

2. Data Component Changes ​

3. Registry Synchronization ​

Phase 6: Implement Logic for New Blocks, Items & Entities ​

1. New Blocks ​

2. New Items ​

3. New Entities ​

Phase 7: Multi-Version & ViaVersion Verification ​

Phase 8: Testing & Verification Checklist ​

Porting to Newer Minecraft Versions

Porting Lifecycle at a Glance

Phase 1: Port the Extractor Mod First (`Pumpkin-MC/Extractor`)

1. Clone or Update the Extractor Repository

2. Update `gradle.properties`

3. Resolve Extractor Compilation Errors

4. Run the Extractor

5. Replace the Old Asset Files in Pumpkin

Phase 2: Update Assets & Datapacks

1. Add the Versioned Datapack

2. Update Versioned Assets

3. Update Bedrock Mappings

4. Decompile Sources for Reverse Engineering (Optional but Recommended)

Phase 3: Register Version Constants & ViaVersion Mappings

1. Declare Version in `pumpkin-util`

2. Declare Version in `pumpkin-codegen`

3. Add ViaVersion / ViaBackwards Mappings

Phase 4: Run Code Generation (`pumpkin-codegen`)

What Gets Regenerated?

Phase 5: Resolve Workspace Compilation Errors

Common Compiler Breakages & Fixes:

1. Packet ID & Layout Changes (`pumpkin-protocol`)

2. Data Component Changes

3. Registry Synchronization

Phase 6: Implement Logic for New Blocks, Items & Entities

1. New Blocks

2. New Items

3. New Entities

Phase 7: Multi-Version & ViaVersion Verification

Phase 8: Testing & Verification Checklist