ci: add flake test

- Check flake
- Check nixos-search doc generation

.cirrus.yml

@@ -29,3 +29,10 @@ task:
         - echo "sandbox = true" >> /etc/nix/nix.conf
         - export NIX_PATH="nixpkgs=$(nix eval --raw -f pkgs/nixpkgs-pinned.nix nixpkgs)"
         - nix run -f '<nixpkgs>' bash coreutils cachix -c ./test/ci/build.sh
+
+    - name: flake
+      container:
+        image: nixpkgs/nix-flakes
+      build_script:
+        - nix flake check
+        - ./test/nixos-search/ci-test.sh

test/nixos-search/ci-test.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "${BASH_SOURCE[0]%/*}"
+
+# Use cachix to cache the `flake-info` build
+cachixCache=nix-bitcoin
+
+nix run .#cachix -- use $cachixCache
+
+# We're running in a basic, unprivileged container that doesn't support sandboxing.
+# Sandboxing is unnneeded because we're only building the 3rd-party `flake-info` tool.
+echo "sandbox = false" >> /etc/nix/nix.conf
+export PATH=$(nix shell -L .#flake-info .#cachix -c sh -c 'echo $PATH')
+
+if [[ ${CACHIX_SIGNING_KEY:-} ]]; then
+    cachix push $cachixCache $(type -P flake-info);
+fi
+
+# flake-info requires '<nixpkgs>'
+export NIX_PATH=nixpkgs=$(nix eval --raw .#nixpkgsPath)
+echo "Running flake-info (nixos-search)"
+flake-info flake ./.

test/nixos-search/flake.nix

@@ -5,5 +5,9 @@
   inputs.nixos-search.url = "github:nixos/nixos-search";
   outputs = { self, nixos-search }: {
     inherit (nixos-search) packages;
+
+    # Used by ./ci-test.sh
+    inherit (nixos-search.inputs.nixpkgs) legacyPackages;
+    nixpkgsPath = toString nixos-search.inputs.nixpkgs;
   };
 }