install-nix-action/install-nix.sh

#!/usr/bin/env bash
set -euo pipefail

if type -p nix &>/dev/null ; then
  echo "Aborting: Nix is already installed at $(type -p nix)"
  exit
fi

# GitHub command to put the following log messages into a group which is collapsed by default
echo "::group::Installing Nix"

# Create a temporary workdir
workdir=$(mktemp -d)
trap 'rm -rf "$workdir"' EXIT

# Configure Nix
add_config() {
  echo "$1" | tee -a "$workdir/nix.conf" >/dev/null
}
# Set jobs to number of cores
add_config "max-jobs = auto"
# Allow binary caches for user
add_config "trusted-users = root $USER"
# Append extra nix configuration if provided
if [[ $INPUT_EXTRA_NIX_CONFIG != "" ]]; then
  add_config "$INPUT_EXTRA_NIX_CONFIG"
fi
if [[ ! $INPUT_EXTRA_NIX_CONFIG =~ "experimental-features" ]]; then
  add_config "experimental-features = nix-command flakes"
fi

# Nix installer flags
installer_options=(
  --no-channel-add
  --darwin-use-unencrypted-nix-store-volume
  --nix-extra-conf-file "$workdir/nix.conf"
)

# only use the nix-daemon settings if on darwin (which get ignored) or systemd is supported
if [[ $OSTYPE =~ darwin || -e /run/systemd/system ]]; then
  installer_options+=(
    --daemon
    --daemon-user-count "$(python3 -c 'import multiprocessing as mp; print(mp.cpu_count() * 2)')"
  )
else
  # "fix" the following error when running nix*
  # error: the group 'nixbld' specified in 'build-users-group' does not exist
  add_config "build-users-group ="
  sudo mkdir -p /etc/nix
  sudo chmod 0755 /etc/nix
  sudo cp $workdir/nix.conf /etc/nix/nix.conf
fi

if [[ $INPUT_INSTALL_OPTIONS != "" ]]; then
  IFS=' ' read -r -a extra_installer_options <<< "$INPUT_INSTALL_OPTIONS"
  installer_options=("${extra_installer_options[@]}" "${installer_options[@]}")
fi

echo "installer options: ${installer_options[*]}"

# There is --retry-on-errors, but only newer curl versions support that
curl_retries=5
while ! curl -sS -o "$workdir/install" -v --fail -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}"
do
  sleep 1
  ((curl_retries--))
  if [[ $curl_retries -le 0 ]]; then
    echo "curl retries failed" >&2
    exit 1
  fi
done

sh "$workdir/install" "${installer_options[@]}"

if [[ $OSTYPE =~ darwin ]]; then
  # macOS needs certificates hints
  cert_file=/nix/var/nix/profiles/default/etc/ssl/certs/ca-bundle.crt
  echo "NIX_SSL_CERT_FILE=$cert_file" >> "$GITHUB_ENV"
  export NIX_SSL_CERT_FILE=$cert_file
  sudo launchctl setenv NIX_SSL_CERT_FILE "$cert_file"
fi

# Set paths
echo "/nix/var/nix/profiles/default/bin" >> "$GITHUB_PATH"
echo "/nix/var/nix/profiles/per-user/$USER/profile/bin" >> "$GITHUB_PATH"

if [[ $INPUT_NIX_PATH != "" ]]; then
  echo "NIX_PATH=${INPUT_NIX_PATH}" >> "$GITHUB_ENV"
fi

# Close the log message group which was opened above
echo "::endgroup::"