yarn-lockfile

Yarn now publishes an official lockfile package at @yarnpkg/lockfile!parse and/or write yarn.lock files

So it turns out...

...that even though yarn doesn't follow the node "small modules" philosophy in terms of making its guts available as packages in the registry, its guts are modules. I've been wanting to make something interoperable with yarn for ages but was put off by its 300 LOC handwritten parser for its proprietary yarn.lock file format.
I don't know why they would invent a new file format when we have working JSON and YAML libraries in every programming language known to man. But until such time they release a library package for working with yarn.lock files, the parser and stringifier can be accessed by directly requiring them from the yarn package:

module.exports = {
  parse: require('yarn/lib/lockfile/parse.js').default,
  stringify: require('yarn/lib/lockfile/stringify.js').default
}

And that's all this module does. It works as you might expect:

const fs = require('fs')
const lockfile = require('yarn-lockfile')

let file = fs.readFileSync('yarn.lock', 'utf8')
let json = lockfile.parse(file)

console.log(json)

let fileAgain = lockfile.stringify(json)

console.log(fileAgain)

Wait, if it's that easy why did you publish this module?

Because the first thing I did when I wanted to parse a yarn.lock was search for "yarn lockfile" on npmjs.org, and when I didn't find one and saw the parser in yarn was handwritten, I gave up. It wasn't until a year later someone made me realize you could do this. Now if someone searches npm for a yarn lockfile parser/stringifier, they will find one. Also, small modules!

License

Copyright 2017 William Hilton. Licensed under The Unlicense.