From 7faa01070b1be9f34215cb6fd3909751397eee60 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io>
Date: Sat, 2 Jan 2021 11:31:14 +0100
Subject: [PATCH] only set experimental features in old nix

---
 direnvrc | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/direnvrc b/direnvrc
index 05819921..8a2c8ef6 100644
--- a/direnvrc
+++ b/direnvrc
@@ -122,6 +122,10 @@ use_nix() {
   local path layout_dir
   path=$("${NIX_BIN_PREFIX}nix-instantiate" --find-file nixpkgs)
   layout_dir=$(direnv_layout_dir)
+  local experimental_flags=()
+  if nix-shell --experimental-features '' --version 2>/dev/null; then
+    experimental_flags+=('--experimental-features' 'nix-command flakes')
+  fi
 
   if [[ "${direnv:-}" == "" ]]; then
     log_status "\$direnv environment variable was not defined. Was this script run inside direnv?"
@@ -155,7 +159,7 @@ use_nix() {
     local dump_cmd tmp
     dump_cmd="echo -n _____direnv_____; \"$direnv\" dump bash"
     tmp=$("${NIX_BIN_PREFIX}nix-shell" \
-      --experimental-features "nix-command flakes" \
+      "${experimental_flags[@]}" \
       --show-trace --pure "$@" --run "$dump_cmd")
     # show original shell hook output
     echo "$tmp" | grep -vP '(?<=_____direnv_____).*'
@@ -173,7 +177,7 @@ use_nix() {
   if [[ "${out:-}" != "" ]] && (( update_drv )); then
     local drv_link="${layout_dir}/drv" drv
     drv=$("${NIX_BIN_PREFIX}nix" show-derivation "$out" \
-      --experimental-features "nix-command flakes" \
+      "${experimental_flags[@]}" \
       | grep -E -o -m1 '/nix/store/.*.drv')
     _nix_add_gcroot "$drv" "$drv_link"
     log_status renewed cache and derivation link