[Core feature request] Allow accessing step outputs

What feature do you need? Please add a link to GitHub docs (https://docs.github.com/en/actions/using-workflows/) which describes the desired feature. https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsid

Do you have an example usage? Best if a YAML snippet is pasted here, or if your project is open-source, an URL to your workflow.

- name: Build and push
  id: docker_build
  uses: docker/build-push-action@v2
  with:
    context: ./
    file: ./Dockerfile
    push: true
    tags: ${{ secrets.DOCKER_HUB_USERNAME }}/discordbot:latest
- name: Image digest
  run: echo ${{ steps.docker_build.outputs.digest }}

even better would be if we could use it somewhat like so:

fun variable(variable: String): String = "\${{ $variable }}"

val dockerBuild = uses(
    name = "Build and push",
    id = "docker_build_push",
    action = DockerBuildPush(
        context = ".",
        file = "./Dockerfile",
        push = true,
        tags = "${variable("secrets.DOCKER_HUB_USERNAME")}/discordbot:latest",
    )
)
run(
    name = "image digest",
    command ="echo ${dockerBuild.outputsVariable("digest")}",
//      command = "echo ${variable("steps.${dockerBuild.id}.outputs.digest")}",
)

but just having access to the id field would let me build the command echo ${{ steps.docker_build.outputs.digest }} myself too

[NikkyAI]

yes the unsafe access way looks good, this could either generate just the steps.docker_build.outputs.digest string… or the whole thing not sure if i might want to call more functions on things eg i might want to do call one of these functions https://docs.github.com/en/actions/learn-github-actions/expressions#functions on the output i could image format or join

[krzema12]

Sure, so I’ll go with dockerBuild.outputs.digest approach.

I was thinking about making dockerBuild.outputs.digest a string that would contain the placeholder, that is ${{steps.docker_build.outputs.digest }}. Would it work for your use case with set-output? If I’m missing something, I’d appreciate a minimal example in YAML and how would you like to do it in Kotlin DSL.

@edit

Now I got your idea about accessing the outputs in an unsafe way. I’ll add API like ${dockerBuild.outputs["yourOutputName"]}. Does it look good?

and would the Action need to implement extra code to map outputs to variables ?

Yes. I’ll come back with a draft implementation and we can discuss various approaches.