build_docker_on_release.yml

name: build Docker image on release

on:
  release:
    types: [published]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v4
        # Some repos have submodules that need to be part of the Docker image
        with:
          submodules: recursive
      - 
        # The release event is a superset of the push tag event, 
        # so we expect two tags to be generated by docker/metadata-action 
        # based on the behaviour for the type=semver,pattern=... tag type:
        # 1. a semver tag vX.Y.Z (from the release Git tag; this is what will be used as the image version in the generated label)
        # 2. latest (as type=semver,pattern=... is part of the latest tag handling)
        # References:
        # - https://github.com/docker/metadata-action?tab=readme-ov-file#typesemver
        # - https://github.com/docker/metadata-action?tab=readme-ov-file#latest-tag
        # - https://github.com/docker/metadata-action/issues/103
        # - https://github.com/docker/metadata-action/issues/168
        name: Docker meta
        id: meta
        uses: docker/metadata-action@v5
        with:
          # TODO: Repos with this wf must have DOCKERHUB_REPO set in the repository variables
          images: ${{ secrets.DOCKERHUB_USERNAME }}/${{ vars.DOCKERHUB_REPO }}
          # NOTE: This input is probably not necessary as the action should generate the appropriate tags
          # based on the default type=ref,event=tag, but we define an explicit pattern here for clarity
          tags: |
            type=semver,pattern={{raw}}
      -
        name: Login to Docker Hub
        uses: docker/login-action@v3
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
      -
        name: Build and push
        uses: docker/build-push-action@v6
        with:
          context: .
          file: ./Dockerfile
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          # Select a subset of labels to apply from https://github.com/opencontainers/image-spec/blob/main/annotations.md#pre-defined-annotation-keys,
          # following https://github.com/docker/metadata-action/issues/303
          labels: |
            org.opencontainers.image.created=${{ fromJSON(steps.meta.outputs.json).labels['org.opencontainers.image.source'] }}
            org.opencontainers.image.revision=${{ fromJSON(steps.meta.outputs.json).labels['org.opencontainers.image.revision'] }}
            org.opencontainers.image.version=${{ fromJSON(steps.meta.outputs.json).labels['org.opencontainers.image.version'] }}