Nix workflow on ubuntu-latest fails at the cachix-action step:
$USER must be set. If running in a container, try setting USER=root.
Error: The process /home/runner/.nix-profile/bin/cachix failed
with exit code 1
cachix shells out to nix-env + cachix use, both of which require
HOME + USER set on the caller. On act_runner the job container does
not propagate USER from the host (it propagates HOME from /tmp/...
but not USER), so cachix exits 1 on a fresh container.
Although cachix-action has continue-on-error: true at the step
level, act_runner appears to bubble the failure up to the job
result anyway — possibly because the step exits before
continue-on-error catches it, or an act_runner deviation from
github-actions semantics. Either way the proper fix is to make
cachix not fail in the first place.
Add a pre-step to the composite action that exports USER for every
subsequent step. id -un resolves to root (the runner runs as root)
or whatever non-root user the container is configured for; falling
back to root if id -un is unavailable.
Test plan: re-run Nix / nix (ubuntu-latest) on the next push to
this branch; expect cachix-action to install + use the cache
successfully, and the job to pass overall.
Tracked next to fix/setup-uv-pin-version (PR #1) — separate concern,
separate PR.
079383e63b