guillaumearm/cc-libs
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
a127a7693e
cc-libs/docs/adrs/adr-0005-craftos-pc-harness.md

4.7 KiB
Raw Blame History

ADR 0005: CraftOS-PC As The Local Harness

Status

Accepted

Date

2026-06-08

Context

This repository targets CC:Tweaked on Minecraft 1.21. The Lua we ship runs inside the ComputerCraft sandbox: it depends on os.pullEventRaw, peripheral, rednet, textutils.serializeJSON, modem channels, and a handful of CC-specific globals. Standard Lua (or LuaJIT) cannot execute this code as-is, so a normal local test harness was never a serious option.

In practice contributors have been running the code in two places:

  • In-game on a real Minecraft server, which is slow to iterate on.
  • In CraftOS-PC (https://www.craftos-pc.cc/), a desktop emulator that ships the same ROM/BIOS as CC:Tweaked, supports modem peripherals via periphemu, and can run fully headless (--cli --headless --script <file>).

CraftOS-PC has been the de facto local harness for months, but that fact lived only as a single line in CLAUDE.md. There was no install guide, no minimum version, and just install did not check that the binary was present. The recent upgrade from v2.6.6 → v2.8.3 (the first one in years) made it obvious that this dependency needed to be made explicit.

Decision

Treat CraftOS-PC as a first-class local development dependency.

  • Minimum version v2.8.3 — recent enough to have the current CC:Tweaked ROM, old enough that contributors already on a 2.8.x build will not be forced to upgrade again immediately.
  • Documented install in docs/install-craftos-pc.md, with a SHA-256-verified macOS flow and pointers to the official Windows/Linux artifacts.
  • Documented upstream navigation in docs/craftos_pc_glossary.md, covering CLI flags, mounts, periphemu, save data, and troubleshooting pages.
  • Verified by just install via a check-craftos recipe that runs craftos --version and requires v2.8.3 or newer. Failure prints a one-line pointer to the install guide instead of a long stack trace.
  • just ci is the local verification entry point. Today it runs check-craftos, check, and test. The installed pre-commit hook invokes just ci directly, and just test owns CraftOS-PC-driven smoke tests.

The existing CLAUDE.md constraint ("Do not run Lua locally or add a test harness unless asked") is reframed rather than removed: there is still no standalone Lua harness, and we are not adding a Busted-style test runner. The harness is CraftOS-PC, invoked deliberately.

Consequences

  • Contributors must install CraftOS-PC before just install succeeds. The install guide makes this a 4-step copy/paste on macOS.
  • Contributors should use the local CraftOS-PC glossary first when researching emulator behavior, then follow the linked upstream pages for details.
  • Headless smoke tests live under tests/ and are driven by just test. Today there are two: tests/boot.lua (prints a marker and shuts down — proves the BIOS started) and tests/ready.lua (round-trips a craftos-ready event through os.queueEvent / os.pullEventRaw — proves the CC event queue works). Each is invoked as craftos --headless --script <file> and its stdout is grepped for __READY__. Adding a third test means dropping a Lua file in tests/ and adding it to the loop in the test: recipe.
  • The macOS install symlinks the binary into /usr/local/bin, which makes CraftOS-PC unable to auto-discover the ROM that ships inside the .app bundle (Could not mount ROM). The test: recipe works around this by passing --rom /Applications/CraftOS-PC.app/Contents/Resources on Darwin. Linux (AppImage) and Windows (installer) auto-discover correctly, so no flag is passed there.
  • The harness version becomes a project-level concern. When CC:Tweaked ships breaking changes that require a newer CraftOS-PC build, we bump the minimum version in docs/install-craftos-pc.md and check-craftos keeps contributors honest.
  • No CI integration yet. Running CraftOS-PC headless in GitHub Actions is feasible (the AppImage works on Ubuntu runners) but is out of scope here; the contract is local-only for now.

Future Work

  • API-loading smoke test. Extend the tests/ set with a script that mounts the repo into the VM (--mount-ro /cc-libs=.) and requires /apis/eventloop, /apis/net, and the router, asserting the wiring loads without errors. Today's smokes only prove CraftOS-PC itself works, not that our code loads inside it.
  • CI. Run just test on push using the Linux AppImage.
  • Pinned ROM. CraftOS-PC ships its own copy of the CC:Tweaked ROM per release. If we ever need to test against a specific in-game version, point CraftOS-PC at a vendored ROM via --rom (the same flag we already pass on macOS for a different reason).