Publishing a Ruby Gem to the GitHub Package Registry

When trying to publish a new gem to the GitHub package registry I received the following error:

Unable to push RubyGem to Package Registry (The expected resource was not found)

After doing some digging, it looks as though you cannot publish gems with any name you like to the package registry.

If you're using the GITHUB_SECRET token in GitHub Actions, the gem name and repo name must match exactly. If your repo is michael-test-org/my_gem then the gem must be named my_gem.

If you're using a personal access token you have a little more flexibility. You can publish gems that match any repository within your organisation, not just the repository that the workflow is running for.

If you're looking for a workflow to publish gems, here are the relevant steps:

yaml
name: Publish Gem
on:
  push:
    tags:
      - "v*"
jobs:
  build:
    runs-on: ubuntu-18.04
    steps:
      - uses: actions/checkout@v2
      - name: Ruby gem cache
        uses: actions/cache@v2
        with:
          path: ${{ github.workspace }}/vendor/bundle
          key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
          restore-keys: |
            ${{ runner.os }}-gems-
      - name: Bundle Setup
        run: |
          gem install --no-document bundler
          bundle config path ${{ github.workspace }}/vendor/bundle
      - name: Bundle Install
        run: bundle install --jobs 4 --retry 3
      - name: Set Credentials
        run: |
          mkdir -p $HOME/.gem
          touch $HOME/.gem/credentials
          chmod 0600 $HOME/.gem/credentials
          printf -- "---\n:github: Bearer ${GITHUB_TOKEN}\n" > $HOME/.gem/credentials
        env:
          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
      - name: Publish to GitHub Packages
        run: |
          export OWNER=$( echo ${{ github.repository }} | cut -d "/" -f 1 )
          gem build station.gemspec
          gem push --KEY github --host https://rubygems.pkg.github.com/${OWNER} *.gem
          gem push *.gem