#!/bin/sh
# CI's "nix flake check" job: the same coverage as `nix flake check` on
# x86_64-linux, as two processes so the evaluator has exited before any build
# starts and no single evaluator holds the whole suite's heap.
#
# 1. nix-eval-jobs evaluates every check, package, dev shell, the formatter
#    and each nixosConfiguration's toplevel, one worker at a time. A worker
#    past --max-memory-size is replaced after its current attribute, so the
#    peak is about the cap plus the heaviest single attribute.
# 2. nix build builds the checks' derivations. The other attributes are
#    evaluated only, as `nix flake check` does.
#
# nix-eval-jobs reports an evaluation error as an `error` field on that
# attribute's line, not as its exit status, so this script fails on any.
#
# Needs nix-eval-jobs and jq on PATH; ci.yml takes both from the flake's
# pinned nixpkgs.
set -eu

system=x86_64-linux
work="$(mktemp -d)"
trap 'rm -rf "$work"' EXIT

nix-eval-jobs \
  --workers 1 \
  --max-memory-size 4096 \
  --gc-roots-dir "$work/gcroots" \
  --flake . \
  --select "flake: let o = flake.outputs; group = s: s // { recurseForDerivations = true; }; in {
    checks = group o.checks.$system;
    packages = group o.packages.$system;
    devShells = group o.devShells.$system;
    formatter = o.formatter.$system;
    nixosConfigurations = group (builtins.mapAttrs (_: c: c.config.system.build.toplevel) o.nixosConfigurations);
  }" >"$work/jobs.json"

jq -r 'select(has("error")) | "\(.attr): \(.error)"' "$work/jobs.json" >"$work/errors"
if [ -s "$work/errors" ]; then
  echo "evaluation failed for $(jq -s 'map(select(has("error"))) | length' "$work/jobs.json") attribute(s):" >&2
  cat "$work/errors" >&2
  exit 1
fi

jq -r 'select(.attrPath[0] == "checks") | .drvPath + "^*"' "$work/jobs.json" >"$work/build"
if [ ! -s "$work/build" ]; then
  echo "nix-eval-jobs returned no checks; the --select expression matched nothing" >&2
  exit 1
fi
echo "evaluated $(jq -s length "$work/jobs.json") attributes; building $(wc -l <"$work/build") checks"

set --
while IFS= read -r drv; do
  set -- "$@" "$drv"
done <"$work/build"
nix build --no-link --keep-going "$@"