Releasing a Library to NPM

Releasing software packages to a registry makes me nervous. My ideal workflow for releasing a library to npm involves several steps:

1. Bump the version number,
2. Create builds (if they are committed to the repository),
3. Commit the changes,
4. Create a Git tag, and
5. Publish the build to the registry.

Chances are, I forget one of these steps or I would carry them out in the wrong order. Fortunately, there are tools available to reduce the workload involved. You can combine them to a build pipeline that suits your needs.

For shipping software to NPM, npm-version gets you almost all the way to publish software using just one command. Used out-of-the-box, npm-version bumps the package’s version number and creates a commit and a git tag with the same version. npm-version also comes with additional scripts, which you can use to do additional things:

• preversion runs before the version is bumped. I use it to check if we’re trying to publish from master; otherwise, the script exits with an error. Other people use it to run tests or linting.
• version runs right after the version is bumped but before the version is committed. Normally, it’s used to create the builds.
• postversion runs after the version commit. You clean up the file system here or push the commit and tags to the Git repository.

The set up I’m using with Leaflet.Deflate looks like this:

{
  "scripts": {
    "preversion": "if [[ \"$(git rev-parse --abbrev-ref HEAD)\" != \"master\" ]]; then echo \"Not on master\" && exit 1; fi",
    "version": "npm run dist && git add -A ./dist",
    "postversion": "git push && git push --tags"
  }
}

Before the publication to NPM, I like to double-check that the build is OK on a clean machine. I hand off the publication of the release to TravisCI, which runs the tests before publishing. Then TravisCI releases the package to NPM.

For cases when I don’t stick to the process and create a tag manually on the GitHub website I added checks to verify that the version number matches the Git tag and that the build files are committed:

PACKAGE_VERSION=$(node -p -e "require('./package.json').version")
if [[ "$PACKAGE_VERSION" != "$TRAVIS_TAG" ]]; then
  echo "Git and NPM versions do not match. Have you updated package.json?"
  exit 1
fi;

npm run build
if [[ $(git diff) ]]; then
  echo "Looks like you haven't committed the new build yet."
  exit 1
fi;