[shikanime]

Why

cachix daemon stop returns before the daemon's upload queue drains, so a large path can be reported as Pushing … in the post step, the job can go green, and the path can still be missing from the cache. Every job involved looks successful; the loss only shows up later as a cache miss. #221 has the evidence: a 4.07 GiB dockerTools.buildImage tarball logged Pushing at 23:51:04, the daemon was stopped at 23:51:17, and its narinfo answered 404 on both caches, while a small path from the same post step answered 200.

The CLI-level fix — draining the queue before daemon stop returns, or reporting what could not be pushed — is still the better one. This change makes the action correct regardless.

What

• Daemon mode now records the pre-build store listing, the same way store-scan mode does.
• After the daemon stops, the post step sweeps the store once with the existing push-paths.sh diff. cachix push skips paths already in the cache (narinfoExists → onAlreadyPresent in Cachix/Client/Push.hs), so this uploads only what the daemon dropped and costs one HEAD per new path when nothing was lost.
• The daemon stop moves into stopDaemon(), so the sweep also runs when the daemon never started or has no pid — cases that previously ended the push with nothing landed.
• Store-scan mode and the listing share pushNewPaths() and recordPreBuildPaths(), which removes the duplicated block from the switch.

Verification

pnpm build bundles the patch into dist/index.js. Same harness for both bundles, only the bundle differs: the post step runs with STATE_pushMode=Daemon and no daemon directory, a stub cachix records its calls, the listing before the build holds /nix/store/old, and the listing after it holds /nix/store/old and /nix/store/built.

baseline (v17): FAIL — nothing pushed, cache silently stays empty
  cachix calls: 0
patched: PASS — the sweep pushed the missing path
  cachix push -j8 smoke <<< /nix/store/built

Both runs log ::error::Cachix Daemon not started. Skipping push first; only the patched bundle reaches the sweep. The action's own fixture (nix-build tests) covers the daemon path end to end in CI.

References

• Daemon mode: a built path logs "Pushing" and then 404s in the cache #221 — report, with the same job before and after the push-mode change
• https://github.com/shikanime-labs/machines/actions/runs/39691368866/job/119541484591 — daemon run, arm tarball 404 after Pushing
• https://github.com/shikanime-labs/machines/actions/runs/39768072566 — store-scan run, same path 200 after 72 s
• https://github.com/cachix/cachix/blob/master/cachix/src/Cachix/Client/Push.hs — push skips cached paths

[sandydoo]

This is undesirable for several reasons, particularly in cases where the store is persisted between runs.