clean_cache.yml

# https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#force-deleting-cache-entries
name: Cleanup caches for closed pull requests

on:
  pull_request:
    types:
      - closed
  schedule:
    - cron: "0 0 */3 * *"
  workflow_dispatch:

jobs:
  cleanup:
    runs-on: ubuntu-latest
    permissions:
      actions: write
      pull-requests: read

    steps:
      - name: Cleanup
        shell: bash
        run: |
          set -euo pipefail

          if [[ "$EVENT_NAME" == "pull_request" ]]; then
            ref="refs/pull/$PR_NUMBER/merge"
            echo "Deleting caches for closed pull request $PR_NUMBER"
            gh cache delete --all --succeed-on-no-caches --repo "$REPO" --ref "$ref"
            exit 0
          fi

          echo "Finding caches for closed pull requests"
          refs=$(gh cache list --repo "$REPO" --limit 1000 --json ref --jq '.[].ref' | sort -u)

          while IFS= read -r ref; do
            [[ "$ref" =~ ^refs/pull/([0-9]+)/merge$ ]] || continue
            pr_number="${BASH_REMATCH[1]}"
            state=$(gh pr view "$pr_number" --repo "$REPO" --json state --jq '.state')

            if [[ "$state" == "CLOSED" ]]; then
              echo "Deleting caches for closed pull request $pr_number"
              gh cache delete --all --succeed-on-no-caches --repo "$REPO" --ref "$ref"
            fi
          done <<< "$refs"
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          EVENT_NAME: ${{ github.event_name }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
          REPO: ${{ github.repository }}