name: release-please-sha-drift

# Guards against the failure mode fixed in PR #9517: release-please's
# `last-release-sha` in release-please-config.json is a STATIC pin that floors
# release-please's GraphQL "fetch merge commits" walk. Nobody advances it
# automatically, so the scan window grows every release and eventually the
# GraphQL query times out ("Something went wrong while executing your query"),
# failing the release-please job.
#
# This check measures how far last-release-sha is behind HEAD and fails loudly
# while there is still plenty of headroom, turning a silent release-breaking
# timeout into an early, obvious signal. The fix when it fires is a one-line
# bump of last-release-sha to the OLDEST current package release commit (never
# newer than any package's last release, or that package's unreleased commits
# get dropped).

on:
  schedule:
    # Mondays 14:00 UTC — proactive, since drift accrues with no config change.
    - cron: '0 14 * * 1'
  workflow_dispatch:
  pull_request:
    branches:
      - main
    paths:
      - 'release-please-config.json'

permissions:
  contents: read

concurrency:
  group: release-please-sha-drift-${{ github.ref }}
  cancel-in-progress: true

jobs:
  check-drift:
    runs-on: ubuntu-latest
    timeout-minutes: 10
    permissions:
      contents: read
    steps:
      - name: Checkout (full history)
        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
        with:
          # Need full history to measure the distance from last-release-sha to HEAD.
          fetch-depth: 0

      - name: Check last-release-sha drift
        env:
          # Fail before the GraphQL scan gets near the size that timed out (~468
          # commits in the #9517 incident; 144 still scanned fine). 250 leaves
          # margin to bump the pin without a fire drill.
          MAX_DRIFT: '250'
        run: |
          set -euo pipefail

          sha="$(jq -r '."last-release-sha" // empty' release-please-config.json)"
          if [[ -z "$sha" ]]; then
            echo "::notice::no last-release-sha configured in release-please-config.json; nothing to check"
            exit 0
          fi

          if ! git cat-file -e "${sha}^{commit}" 2>/dev/null; then
            echo "::error file=release-please-config.json::last-release-sha ${sha} is not a reachable commit"
            exit 1
          fi

          behind="$(git rev-list --count "${sha}..HEAD")"
          echo "last-release-sha ${sha} is ${behind} commits behind HEAD (threshold ${MAX_DRIFT})"

          if (( behind > MAX_DRIFT )); then
            echo "::error file=release-please-config.json::release-please last-release-sha is ${behind} commits behind HEAD (> ${MAX_DRIFT}). The release-please merge-commit scan will eventually time out (see PR #9517). Advance last-release-sha to the OLDEST current package release commit — never newer than any package's last release, or that package loses its unreleased commits."
            exit 1
          fi

          echo "::notice::release-please last-release-sha drift OK (${behind} <= ${MAX_DRIFT})"