Dynamic selection of GitHub Runners - as GitHub Action matrix builds currently do not allow dynamic values

dynamic-runner-selection.yaml

name: CI
on:
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]

jobs:

  build:
    runs-on: ubuntu-latest
    outputs:
      runner: ${{ steps.runner.outputs.runner }}

    steps:
    - id: runner
      run: echo "::set-output name=runner::macos-latest"

  test:
    needs: [build]
    runs-on: ${{ needs.build.outputs.runner }}
    steps:
      - run: echo I Ran

Hi @jonico, can we do multiple tags? I tried the similar as above, the value of outouts.runner is [ tag1, tag2 ], but it treats outouts.runner as a whole string, instead of an array of tags.

@truonghuynguyen: you could experiment with outputs in list format similar to https://github.com/jonico/visualize-actions-matrix-builds-on-k8s/blob/master/.github/workflows/visualize-matrix-build-led.yml#L58

@truonghuynguyen, I have exactly same needs, and it works for me:

runs-on: [ self-hosted, "${{ needs.build.outputs.runner }}" ]

Unfortunately, I couldn't find how to attach several runners dynamically.
I didn't test but, If you have fixed number of runners, than you might try like this:

runs-on: [ self-hosted, "${{ needs.build.outputs.runner1 }}", "${{ needs.build.outputs.runner2 }}" ]

This was super helpful for a project I'm working on, thanks! 🎉

@truonghuynguyen, I have exactly same needs, and it works for me:

runs-on: [ self-hosted, "${{ needs.build.outputs.runner }}" ]

Unfortunately, I couldn't find how to attach several runners dynamically. I didn't test but, If you have fixed number of runners, than you might try like this:

runs-on: [ self-hosted, "${{ needs.build.outputs.runner1 }}", "${{ needs.build.outputs.runner2 }}" ]

Works fine for me, thanks!! 🎉🎉