tests: run flake-info in sandbox

Don't use sandboxing in Cirrus CI where namespace support is missing.

test/nixos-search/flake-info-sandboxed.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Run flake-info for the nix-bitcoin flake in a sandbox:
+# - Adds a consistent, reproducible runtime environment
+# - Removes the need to trust the flake-info binary
+#
+# Use bubblewrap instead of a sandboxed Nix build so that we don't have to copy
+# the whole repo to the sandbox when running this test.
+
+cd "${BASH_SOURCE[0]%/*}"
+
+nbFlake=$(realpath ../..)
+
+# shellcheck disable=SC2016
+PATH=$(nix shell -L .#{flake-info,bubblewrap} -c sh -c 'echo $PATH')
+
+tmpDir=$(mktemp -d /tmp/nix-bitcoin-flake-info.XXX)
+trap 'rm -rf $tmpDir' EXIT
+
+echo '
+experimental-features = nix-command flakes
+flake-registry = /dev/null
+' > "$tmpDir/nix.conf"
+
+echo "Running flake-info (nixos-search)"
+
+bwrap \
+  --unshare-all \
+  --clearenv \
+  --setenv PATH "$PATH" \
+  --setenv NIX_PATH "$NIX_PATH" \
+  --bind "$tmpDir" / \
+  --proc /proc \
+  --dev /dev \
+  --tmpfs /tmp \
+  --ro-bind "$nbFlake" "$nbFlake" \
+  --ro-bind /nix /nix \
+  --ro-bind /etc /etc \
+  --tmpfs /etc/nix \
+  --ro-bind "$tmpDir/nix.conf" /etc/nix/nix.conf \
+  --ro-bind /usr /usr \
+  --ro-bind-try /run /run \
+  -- flake-info flake "$nbFlake"

test/run-tests.sh

@@ -286,8 +286,7 @@ nixosSearch() {
         # Add gcroots for flake-info
         nix build "$scriptDir/nixos-search#flake-info" -o "$outLinkPrefix-flake-info"
     fi
-    echo "Running flake-info (nixos-search)"
-    nix run "$scriptDir/nixos-search#flake-info" -- flake "$scriptDir/.."
+    "$scriptDir/nixos-search/flake-info-sandboxed.sh"
 }
 
 # A basic subset of tests to keep the total runtime within