Create an Addon Core

An addon core is an ordinary script folder owned by your extension. It centralizes behavior shared by several machines without changing DoriosCore.

The template calls this folder ExampleCore so its purpose is visible. Rename it for a real project, for example:

ExampleCore       -> MYADDON_CORE
ThermalMachine    -> keep this name or choose an addon-specific class name

MYADDON_CORE is a naming convention, not another required dependency. It is compiled and distributed as part of your Behavior Pack.

What belongs in it

Put in the addon core	Keep in a concrete feature folder
Classes reused by multiple addon machines	One block's component registration
Addon-wide processing helpers	One machine's recipe table
Shared formulas and validation	Block, item, and entity JSON
Addon-owned storage mechanics	UI JSON and localization
Small public exports	Registrations that must run at startup

Registration modules normally stay outside the core because importing a class should not unexpectedly register blocks or content.

1. Create the folder structure

Use the template structure as a starting point:

BP/scripts/MYADDON_CORE

MYADDON_CORE/
├── index.js
├── README.md
├── machinery/
│   ├── ThermalMachine.js
│   └── MyGasGenerator.js
└── processing/
    ├── processCycle.js
    └── recipeTemplates.js

The folder name should be unique enough that it cannot be confused with DoriosCore. Do not rename or replace the BP/scripts/DoriosCore dependency folder.

2. Define one public entry point

Only export modules intended for other addon scripts:

BP/scripts/MYADDON_CORE/index.js

export * from "./machinery/ThermalMachine.js";
export * from "./machinery/MyGasGenerator.js";
export * from "./processing/processCycle.js";
export * from "./processing/recipeTemplates.js";

This gives concrete machines one stable import path:

import { ThermalMachine, advanceProcessCycle } from "../../MYADDON_CORE/index.js";

The relative path depends on where the importing file is located. DoriosCore remains a package import because Regolith exposes it as a dependency:

import { Machine } from "DoriosCore/index.js";

3. Document the boundary

Add a short README that tells future contributors where changes belong:

BP/scripts/MYADDON_CORE/README.md

# MYADDON_CORE

This folder contains reusable behavior owned by this addon.

- Classes may extend public exports from `DoriosCore/index.js`.
- Helpers may use public exports from `DoriosLib/index.js`.
- Concrete blocks and registrations stay in their feature folders.
- DoriosCore and DoriosLib are read-only dependencies.

This is especially useful when the project is used as a team template.

4. Update imports after renaming

Find every old folder reference:

rg "ExampleCore" BP/scripts

Then update only your addon imports. A template path such as:

import { ThermalMachine } from "../../ExampleCore/index.js";

becomes:

import { ThermalMachine } from "../../MYADDON_CORE/index.js";

Do not change imports like DoriosCore/index.js or DoriosLib/index.js.

5. Keep startup explicit

The Behavior Pack entry point should load registrations and concrete examples deliberately:

BP/scripts/main.js

import "./config/index.js";
import "./examples/index.js";

Concrete modules can import classes from MYADDON_CORE, but main.js does not need to import the core by itself. An exported class has no startup effect until another module uses it.

Dependency direction

Keep imports flowing in one direction:

main.js
  -> config and feature modules
       -> MYADDON_CORE
            -> DoriosCore and DoriosLib public entry points

Avoid importing concrete feature modules back into MYADDON_CORE. That circular dependency makes initialization order harder to understand and can run registrations before their configuration is ready.

Checklist

• The addon-owned folder has a project-specific name.
• index.js exports only reusable public modules.
• Concrete block registration stays outside the core.
• Imports from the core use a correct relative path.
• DoriosCore imports always use DoriosCore/index.js.
• DoriosLib imports always use DoriosLib/index.js.
• No shared dependency file was modified.

Continue with Create a Custom Machine Class.