Generating tags for multiple bake targets

[Pesa]

Description

Let's say I have the following docker-bake.hcl:

group "default" {
  targets = ["foo", "bar"]
}

target "foo" {
  dockerfile = "Dockerfile.foo"
  tags = ["my/foo:latest"]
}

target "bar" {
  dockerfile = "Dockerfile.bar"
  tags = ["my/bar:latest"]
}

The tags listed above function a bit like defaults, i.e., they're used when I run bake locally for testing. On GitHub Actions, however, I'd like to use docker/metadata-action to generate a list of tags based on various criteria (semver, date, etc...). These generated tags should replace the :latest tag from docker-bake.hcl, but I still want to keep the base name of the two images (my/foo and my/bar).

This would be trivial to accomplish with a single target (using the images input), but I didn't find a way to do it for multiple targets, where each target has a distinct image name.

Apologies if I missed something obvious (seems odd that this use case isn't already supported, since the whole point of bake is orchestrating the build of multiple targets).

[crazy-max]

You can use the matrix feature for this purpose, like:

target "default" {
  name = "build-${tgt}"
  matrix = {
    tgt = ["foo", "bar"]
  }
  dockerfile = "Dockerfile.${tgt}"
  tags = ["my/${tgt}:latest"]
}

[Pesa]

@crazy-max sorry, I'm not sure I understand. How would I combine the matrix with the tags generated by docker/metadata-action? If I set:

inherits = ["docker-metadata-action"]

isn't that going to overwrite the whole tag my/${tgt}:latest?

[Pesa]

Basically, I would need something like this:

// docker-bake.hcl

target "default" {
  name = "${tgt}-${version}"
  matrix = {
    tgt = ["foo", "bar"]
    version = [...list of version tags generated by metadata-action...] // ???
  }
  dockerfile = "Dockerfile.${tgt}"
  tags = ["my/${tgt}:${version}"]
}

And then I'd call metadata-action with an empty images input so that it generates raw version tags without base name.

[int128]

I could generate the tags for each target using for expression. Here are examples.

Using string interpolation

      - uses: docker/metadata-action@v5
        id: metadata
      - uses: docker/bake-action@v5
        env:
          TAG_BASE: my/foo # something like ghcr.io/${{ github.repository }}
        with:
          push: true
          files: |
            ./docker-bake.hcl
            ${{ steps.metadata.outputs.bake-file }}

variable "TAG_BASE" {}

target "docker-metadata-action" {}

target "service1" {
  inherits = ["docker-metadata-action"]
  context = "."
  dockerfile = "service1.dockerfile"
  tags = [for tag in target.docker-metadata-action.tags : "${TAG_BASE}/service1:${tag}"]
}

target "service2" {
  inherits = ["docker-metadata-action"]
  context = "."
  dockerfile = "service2.dockerfile"
  tags = [for tag in target.docker-metadata-action.tags : "${TAG_BASE}/service2:${tag}"]
}

It will build the image tags of my/foo/service1:latest and my/foo/service2:latest.

Using replace function

      - uses: docker/metadata-action@v5
        id: metadata
        with:
          images: ghcr.io/${{ github.repository }}/__service__
      - uses: docker/bake-action@v5
        with:
          push: true
          files: |
            ./docker-bake.hcl
            ${{ steps.metadata.outputs.bake-file }}

target "docker-metadata-action" {}

target "service1" {
  inherits = ["docker-metadata-action"]
  context = "."
  dockerfile = "service1.dockerfile"
  tags = [for tag in target.docker-metadata-action.tags : replace(tag, "__service__", "service1")]
}

target "service2" {
  inherits = ["docker-metadata-action"]
  context = "."
  dockerfile = "service2.dockerfile"
  tags = [for tag in target.docker-metadata-action.tags : replace(tag, "__service__", "service2")]
}

[Pesa]

Thanks for the suggestion @int128, I will give it a try.