Packages

Milo's registry is GitHub. There is no central index to sign up for — milo add takes a repository, resolves the highest tag, and writes the exact commit and tree hash into milo.lock.

milo add github.com/milo-language/milo-postgres          # highest release
milo add github.com/milo-language/milo-postgres@v0.1.0   # or pin a tag

Then import it by its package name, which is the repository name minus the milo- prefix:

from "postgres" import { Conn }

Published

Package	Install	What it is
postgres	milo add github.com/milo-language/milo-postgres	PostgreSQL client — wire protocol v3, SCRAM-SHA-256, extended query with real bind parameters, TLS
redis	milo add github.com/milo-language/milo-redis	Redis client — RESP2/RESP3, pipelining, pub/sub, transactions
markdown	milo add github.com/milo-language/milo-markdown	CommonMark + GFM parser and HTML renderer, with a walkable AST
toml	milo add github.com/milo-language/milo-toml	TOML v1.0.0 parser and serializer
yaml	milo add github.com/milo-language/milo-yaml	YAML 1.2 subset parser
json-rpc	milo add github.com/milo-language/milo-json-rpc	JSON-RPC 2.0 over Content-Length framing — the LSP/DAP base protocol
gl	milo add github.com/milo-language/milo-gl	OpenGL 3.3 core bindings and a safe layer
sdl	milo add github.com/milo-language/milo-sdl	SDL2 bindings — video, input, gamepad, audio

How they are graded

Every package here is tested against something that is not itself — an independent implementation, a published test vector, or the real server. A test suite that only compares a library to its own expectations proves that it is self-consistent, not that it is correct.

Package	Graded against
markdown	all 655 CommonMark spec examples, plus byte-identical output to cmark over the whole spec document
toml	Python's tomllib over a 78-file corpus, comparing values and types
postgres	a real PostgreSQL requiring SCRAM, with psql reading back what the client wrote
redis	a real Redis requiring AUTH, with redis-cli cross-checking, and RESP2 vs RESP3 asserted as a differential
yaml	ruamel.yaml

Why these live outside the standard library

std carries JSON, because the toolchain itself reads milo.json and because the slot has one obvious winner. Formats with credible competitors, and clients that track someone else's release cycle, are packages instead — so a fix ships the same day on its own tag rather than waiting for a compiler release.

See the standard library for what is built in.

Publishing your own

A package is a repository with a milo.json and a lib entry point:

{
  "name": "mylib",
  "version": "0.1.0",
  "license": "MIT",
  "repository": "github.com/you/milo-mylib",
  "lib": "lib.milo",
  "targets": ["darwin", "linux", "windows"],
  "exclude": ["tests/**", "examples/**"]
}

Tag a release (git tag v0.1.0 && git push origin v0.1.0) and it is installable. Tag it — without a tag, milo add tracks whatever main happens to be at install time, so two people adding your package on different days get different code.

Then install what you published

A package's own tests import "./lib" or "../lib" — the local path. Nobody who installs your package takes that path; they take the package path, which mangles names per package. The two can disagree, and when they do your CI is green and your users cannot compile at all.

Both failures have happened here, from different causes:

• milo-postgres v0.1.0 shipped with 32 passing tests and did not compile for anyone, because a capitalised global was unresolvable under package mangling.
• milo-yaml v0.2.1 shipped without a fix that was already sitting on main, so the tag milo add resolved to was older than the working code.

Neither is catchable by a package's own test suite. The check that catches both takes ten seconds:

mkdir /tmp/verify && cd /tmp/verify
echo '{ "name": "verify", "version": "0.0.1" }' > milo.json
milo add github.com/you/milo-mylib          # the published artifact, not your checkout
printf 'from "mylib" import { thing }\nfn main() { print(thing()) }\n' > main.milo
milo run main.milo

Run it after tagging, from a directory that is not your repo.