Summary

BREAKING: init-pants now restores caches only (via actions/cache/restore@v5). A new save-pants-cache companion action must be added at the end of the job to persist caches.

Why: actions/cache@v5 saves via a post-step hook that does not run on workflow cancellation. Workflows using cancel-in-progress: true enter a cold-cache cycle — every cancelled run loses its cache save, so the next run starts cold.

Fix: Split restore and save into separate actions. The save step uses if: always() which fires even on cancellation, breaking the cycle.

Changes

• init-pants/action.yaml — Switch actions/cache@v5 → actions/cache/restore@v5, add outputs for cache keys/paths
• save-pants-cache/action.yaml — New companion action using actions/cache/save@v5
• READMEs updated with migration guide

Usage

      - uses: pantsbuild/actions/init-pants@main
        id: pants-init
        with:
          named-caches-hash: ${{ hashFiles('lockfiles/*.json') }}

      # ... build/test steps ...

      - uses: pantsbuild/actions/save-pants-cache@main
        if: always()
        with:
          setup-cache-path: ${{ steps.pants-init.outputs.setup-cache-path }}
          setup-cache-key: ${{ steps.pants-init.outputs.setup-cache-key }}
          named-caches-path: ${{ steps.pants-init.outputs.named-caches-path }}
          named-caches-key: ${{ steps.pants-init.outputs.named-caches-key }}
          named-caches-hash: ${{ steps.pants-init.outputs.named-caches-hash }}
          lmdb-store-path: ${{ steps.pants-init.outputs.lmdb-store-path }}
          lmdb-store-key: ${{ steps.pants-init.outputs.lmdb-store-key }}
          cache-lmdb-store: ${{ steps.pants-init.outputs.cache-lmdb-store }}

Context

Discovered in CI where persistent cold caches occurred despite no code changes between runs. GHA cache keys are immutable, so actions/cache/save is a safe no-op when the key already exists.

Test plan

• init-pants restores caches correctly (setup, named, LMDB)
• save-pants-cache with if: always() saves caches on normal completion
• Cache saves survive cancel-in-progress cancellation
• Cache keys match between init-pants outputs and save-pants-cache inputs