Making add-ons (.mastlib)

An add-on packages reusable MAST (consoles, comms trees, prefabs, routes) so other missions can load it. sbs_utils ships the Legendary Missions add-ons this way. An add-on is a module: a folder with an __init__.mast that imports the rest.

Lay out the module

MyAddon/                 # a dev mission that hosts the add-on
├── script.py            # standard boilerplate
├── story.mast           # minimal test harness (not the add-on)
├── story.json           # sbslib + any mastlibs the add-on needs
├── __lib__.json         # declares the add-on folder for the packager
└── my_addon/            # THE ADD-ON -> becomes my_addon.mastlib
    ├── __init__.mast    # entry point - imports the rest
    ├── panels.mast
    └── helpers.py       # Python helpers are fine too

my_addon/__init__.mast just imports its files:

import panels.mast
import helpers.py

__lib__.json names the folder(s) to package:

{
    "version": "v1.0.0",
    "mastlib": ["my_addon"]
}

Develop, then package

While developing, keep the add-on folder inside a mission — the mission directory is on the MAST search path, so its labels load automatically. When ready to share:

sbs lib MyAddon -u your-github-user      # builds your-github-user.my_addon.v1.0.0.mastlib

Drop the .mastlib in __lib__/ and add it to another mission's story.json:

{ "mastlib": ["your-github-user.my_addon.v1.0.0.mastlib"] }

Its labels, routes, and prefabs are now available globally in that mission. Add-ons are a great way to share partial missions — Gamemaster comms, custom consoles, prefab libraries, and so on. See Sharing reusable Python for the .sbslib side.