name: Cache Service Probe

# Temporary diagnostic for #178, to be deleted once it has answered its
# question. actions/cache refuses to run here, printing its GHES warning, on
# both v3 and v4. Two explanations remain and they need different fixes:
#
#   1. Cache is off in act_runner's config, so no ACTIONS_CACHE_URL is exported
#      and the runner has nothing to point a patched bundle at. Fix is
#      cache.enabled in config.yaml.
#   2. Cache is served, but the runner's bundle patcher does not recognise
#      these bundles and so leaves the GHES gate shut. That is a runner bug
#      worth reporting upstream.
#
# An exported cache URL tells the two apart.

on:
  pull_request:
  workflow_dispatch:

jobs:
  probe:
    name: Cache Service Probe
    runs-on: ubuntu-latest
    steps:
      # Values for the URLs, which are plain endpoints, and presence only for
      # the tokens, which are credentials and must not reach the log.
      - name: Report cache-related environment
        run: |
          echo "GITHUB_SERVER_URL        = ${GITHUB_SERVER_URL:-<unset>}"
          echo "ACTIONS_CACHE_URL        = ${ACTIONS_CACHE_URL:-<unset>}"
          echo "ACTIONS_RESULTS_URL      = ${ACTIONS_RESULTS_URL:-<unset>}"
          echo "ACTIONS_CACHE_SERVICE_V2 = ${ACTIONS_CACHE_SERVICE_V2:-<unset>}"
          for t in ACTIONS_RUNTIME_TOKEN ACTIONS_CACHE_TOKEN GITHUB_TOKEN; do
            if [ -n "${!t:-}" ]; then echo "$t: set"; else echo "$t: unset"; fi
          done

      # Names only, never values — catches any endpoint variable the runner
      # exports under a name this probe did not think to ask for.
      - name: List ACTIONS_/GITHUB_ variable names
        run: env | grep -E '^(ACTIONS_|GITHUB_)' | sed 's/=.*//' | sort

      # Run the real thing alongside, so the warning and the environment that
      # produced it sit in one log.
      - name: Try actions/cache
        uses: actions/cache@v4
        with:
          path: /tmp/cache-probe
          key: cache-probe-${{ github.run_id }}

      - name: Runner and version context
        run: |
          echo "runner.arch = ${{ runner.arch }}"
          echo "runner.os   = ${{ runner.os }}"

  # The first probe showed ACTIONS_CACHE_URL unset but ACTIONS_RESULTS_URL set,
  # i.e. the runner serves the v2 cache service and not v1. actions/cache v4.3
  # can speak v2, but only when ACTIONS_CACHE_SERVICE_V2 is set, and it is not.
  # These three variants test the ways round that.
  variant-v4-flag:
    name: cache@v4 + ACTIONS_CACHE_SERVICE_V2
    runs-on: ubuntu-latest
    env:
      ACTIONS_CACHE_SERVICE_V2: "true"
    steps:
      - run: mkdir -p /tmp/probe && head -c 1048576 /dev/urandom > /tmp/probe/blob
      - uses: actions/cache@v4
        with:
          path: /tmp/probe
          key: probe-v4flag-${{ github.run_id }}

  variant-v6:
    name: cache@v6
    runs-on: ubuntu-latest
    steps:
      - run: mkdir -p /tmp/probe && head -c 1048576 /dev/urandom > /tmp/probe/blob
      - uses: actions/cache@v6
        with:
          path: /tmp/probe
          key: probe-v6-${{ github.run_id }}

  variant-v6-flag:
    name: cache@v6 + ACTIONS_CACHE_SERVICE_V2
    runs-on: ubuntu-latest
    env:
      ACTIONS_CACHE_SERVICE_V2: "true"
    steps:
      - run: mkdir -p /tmp/probe && head -c 1048576 /dev/urandom > /tmp/probe/blob
      - uses: actions/cache@v6
        with:
          path: /tmp/probe
          key: probe-v6flag-${{ github.run_id }}