go-versions.yml

# The following chunk of yml boils down to pulling two Go version numbers out of a file and
# making them available to the other workflows in a convenient fashion.
#
# It's a reusable workflow instead of an action so that its output can be used in a matrix strategy
# of another job.
#
# The idea is to define the most recent, and penultimate, Go versions that should be used to test Relay.
# Ideally we'd define these in a single place - otherwise we'd need to update many different places in
# each workflow. This single place is .github/variables/go-versions.env.
#
# This reusable workflow grabs them out of the file, then sets them as outputs. As a convenience, it
# also wraps each version in an array, so it can be directly used in a matrix strategy. Single-item matrices
# are nice because you can tell instantly in the Github UI which version is being tested without needing
# to inspect logs.
#
# To use a matrix output, e.g. latest version, do:
#  strategy:
#    matrix: ${{ fromJSON(this-job.outputs.latest-matrix) }}
#
name: Go Versions
on:
  workflow_call:
    outputs:
      latest:
        description: 'The most recent Go version to test'
        value: ${{ jobs.go-versions.outputs.latest }}
      penultimate:
        description: 'The second most recent Go version to test'
        value: ${{ jobs.go-versions.outputs.penultimate }}
      min:
        description: 'The minimum Go version to test'
        value: ${{ jobs.go-versions.outputs.min }}
      matrix:
        description: 'All Go versions to test as a matrix'
        value: ${{ jobs.go-versions.outputs.all }}

jobs:
  go-versions:
    runs-on: ubuntu-latest
    outputs:
      latest: ${{ steps.set-env.outputs.latest }}
      penultimate: ${{ steps.set-env.outputs.penultimate }}
      all: ${{ steps.set-matrix.outputs.all }}
    steps:
      - uses: actions/checkout@v4
      - name: Set Go Versions
        id: set-env
        run:  cat ./.github/variables/go-versions.env > $GITHUB_OUTPUT
      - name: Set Go Version Matrices
        id: set-matrix
        run: |
          echo "all=[\"${{ steps.set-env.outputs.latest }}\",\"${{ steps.set-env.outputs.penultimate }}\",\"${{ steps.set-env.outputs.min }}\"]" >> $GITHUB_OUTPUT