It took me way too long and far too many Travis-CI builds to figure out the right configuration for Travis-CI to run lerna publish with everything it needed. I'm still not 100% sure if everything I'm doing is necessary, but perhaps it will help others to share my findings. Even better if there was some documentation around this.

My goals

1. Automatically npm publish each relevant package in the monorepo when a PR is merged into master.
2. Automatically cut a release by pushing a publish commit via git push.
3. Only do the above on Travis-CI builds on the master branch.

Solution

Add .npmrc to .gitignore.

.travis.yml

after_success:
  - echo "//registry.npmjs.org/:_authToken=${NPM_TOKEN}" > ~/.npmrc
  - git remote add pub https://${GH_TOKEN}@github.com/${TRAVIS_REPO_SLUG}.git
  - git fetch pub master # needed?
  - git checkout master # got an error w/o this one

deploy:
  - provider: script
    script: npx lerna publish --git-remote pub
    skip_cleanup: true
    keep_history: true
    on:
      branch: master

Shouldn't the GH_TOKEN and TRAVIS_REPO_SLUG automatically be used in the first place? I'm hoping there's an easier way to compress these steps.

lerna.json

{
  "packages": ["packages/*"],
  "version": "independent",
  "command": {
    "publish": {
      "conventionalCommits": true,
      "yes": true // Needed in the CI env? I don't want to wait for another build to find out.
    }
  }
}

Conclusion

Be great if there was some documentation around all these steps together.