name: CI repro (readLinkAt)

# Throwaway workflow to reproduce the determinate-nix `readLinkAt.works` unit
# test failure seen in the master CI build, and capture the full gtest log.
# Runs only on this branch; delete the branch when done.

on:
  push:
    branches: [ci-repro-readlinkat]

jobs:
  repro:
    name: Reproduce determinate-nix test failure
    runs-on: ubuntu-26.04
    steps:
      - uses: actions/checkout@v6
      - uses: DeterminateSystems/determinate-nix-action@v3
        with:
          github-token: ${{ secrets.GH_PULL_TOKEN }}
          extra-conf: |
            sandbox-fallback = false
            cores = 6

            lazy-trees = true
            eval-cores = 0

            accept-flake-config = true
            extra-substituters = https://nix-cache.nul.ie
            extra-trusted-public-keys = nix-cache.nul.ie-1:BzH5yMfF4HbzY1C977XzOxoPhEc9Zbu39ftPkUbH+m4=

      - name: Nix build-dir / store settings
        run: |
          echo "===== nix config (build-dir / store / sandbox) ====="
          nix config show 2>/dev/null | grep -iE 'build-dir|store|sandbox|temp' || true
          echo "===== TMPDIR/env ====="
          echo "TMPDIR=$TMPDIR RUNNER_TEMP=$RUNNER_TEMP GITHUB_WORKSPACE=$GITHUB_WORKSPACE HOME=$HOME"

      - name: Mount table
        run: |
          echo "===== df -T ====="
          df -T || df -h
          echo "===== mount ====="
          mount 2>/dev/null | grep -iE 'overlay|tmpfs|/nix|ext4|xfs|btrfs|9p|fuse' || mount

      - name: Symlink-length probe
        run: |
          # Determine, per candidate dir, the longest symlink target that can be
          # created (the test needs PATH_MAX/2 = 2048 and PATH_MAX-1 = 4095).
          probe() {
            local d="$1"
            [ -d "$d" ] || { echo "  $d: (absent)"; return; }
            local fstype; fstype=$(stat -f -c %T "$d" 2>/dev/null || echo '?')
            local res=""
            for n in 256 1000 2048 3000 4095; do
              local tgt; tgt=$(head -c "$n" < /dev/zero | tr '\0' 'y')
              if ln -sf "$tgt" "$d/.symtest.$n" 2>/dev/null; then res="$res $n"; else res="$res !$n"; fi
              rm -f "$d/.symtest.$n" 2>/dev/null || true
            done
            echo "  $d [$fstype]:$res"
          }
          echo "===== max symlink target length per dir (n = ok, !n = ENAMETOOLONG) ====="
          for d in /tmp /var/tmp /dev/shm /nix /nix/var "$HOME" "$RUNNER_TEMP" "$GITHUB_WORKSPACE" /root /build; do
            probe "$d"
          done