graceful fallback if no nixpkgs is in NIX_PATH

direnvrc

@@ -252,27 +252,29 @@ use_flake() {
 use_nix() {
   _nix_direnv_preflight
 
-  local layout_dir path
-  path=$(_nix_direnv_realpath "$("${NIX_BIN_PREFIX}nix-instantiate" --find-file nixpkgs)")
+  local layout_dir path version
   layout_dir=$(direnv_layout_dir)
+  path=$("${NIX_BIN_PREFIX}nix-instantiate" --find-file nixpkgs 2>/dev/null)
+  if [[ -n "$path" ]]; then
+    path=$(_nix_direnv_realpath "$path")
 
-  local version
-  if [[ -f "${path}/.version-suffix" ]]; then
-    version=$(< "${path}/.version-suffix")
-  elif [[ -f "${path}/.git/HEAD" ]]; then
-    local head
-    read -r head < "${path}/.git/HEAD"
-    local regex="ref: (.*)"
-    if [[ "$head" =~  $regex ]]; then
-      read -r version < "${path}/.git/${BASH_REMATCH[1]}"
-    else
-      version="$head"
+    if [[ -f "${path}/.version-suffix" ]]; then
+      version=$(< "${path}/.version-suffix")
+    elif [[ -f "${path}/.git/HEAD" ]]; then
+      local head
+      read -r head < "${path}/.git/HEAD"
+      local regex="ref: (.*)"
+      if [[ "$head" =~  $regex ]]; then
+        read -r version < "${path}/.git/${BASH_REMATCH[1]}"
+      else
+        version="$head"
+      fi
+    elif [[ -f "${path}/.version" && "${path}" == "/nix/store/"* ]]; then
+      # borrow some bits from the store path
+      local version_prefix
+      read -r version_prefix < "${path}/.version"
+      version="${version_prefix}-${path:11:16}"
     fi
-  elif [[ -f "${path}/.version" && "${path}" == "/nix/store/"* ]]; then
-    # borrow some bits from the store path
-    local version_prefix
-    read -r version_prefix < "${path}/.version"
-    version="${version_prefix}-${path:11:16}"
   fi
 
   local profile

tests/direnv_project.py

@@ -40,6 +40,8 @@ def direnv_project(test_root: Path, project_root: Path) -> Iterator[DirenvProjec
     with TemporaryDirectory() as _dir:
         dir = Path(_dir) / "proj"
         shutil.copytree(test_root / "testenv", dir)
+        shutil.copyfile(project_root / "flake.nix", dir / "flake.nix")
+        shutil.copyfile(project_root / "flake.lock", dir / "flake.lock")
         nix_direnv = project_root / "direnvrc"
 
         c = DirenvProject(Path(dir), nix_direnv)

tests/procs.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 
 import subprocess
-from typing import List, Union, IO, Any
+from typing import List, Union, IO, Any, Optional
 from pathlib import Path
 
 
@@ -16,10 +16,11 @@ def run(
     cwd: _DIR = None,
     stderr: _FILE = None,
     stdout: _FILE = None,
+    env: Optional[dict[str, str]] = None,
 ) -> subprocess.CompletedProcess:
     if cwd is not None:
         print(f"cd {cwd}")
     print("$ " + " ".join(cmd))
     return subprocess.run(
-        cmd, text=text, check=check, cwd=cwd, stderr=stderr, stdout=stdout
+        cmd, text=text, check=check, cwd=cwd, stderr=stderr, stdout=stdout, env=env
     )

tests/test_use_nix.py

@@ -1,20 +1,27 @@
 #!/usr/bin/env python2
 
 import sys
+import os
 import subprocess
 import unittest
+from typing import Optional
 
 from procs import run
 from direnv_project import DirenvProject
 
 
-def direnv_exec(direnv_project: DirenvProject, cmd: str) -> None:
+def direnv_exec(
+    direnv_project: DirenvProject, cmd: str, env: Optional[dict[str, str]] = None
+) -> None:
+    args = ["direnv", "exec", str(direnv_project.dir), "sh", "-c", cmd]
+    print("$ " + " ".join(args))
     out = run(
-        ["direnv", "exec", str(direnv_project.dir), "sh", "-c", cmd],
+        args,
         stderr=subprocess.PIPE,
         stdout=subprocess.PIPE,
         check=False,
         cwd=direnv_project.dir,
+        env=env,
     )
     sys.stdout.write(out.stdout)
     sys.stderr.write(out.stderr)
@@ -28,6 +35,13 @@ def test_attrs(direnv_project: DirenvProject) -> None:
     direnv_exec(direnv_project, "echo $THIS_IS_A_SUBSHELL")
 
 
+def test_no_nix_path(direnv_project: DirenvProject) -> None:
+    direnv_project.setup_envrc("use nix --argstr someArg OK")
+    env = os.environ.copy()
+    del env["NIX_PATH"]
+    direnv_exec(direnv_project, "echo $SHOULD_BE_SET", env=env)
+
+
 def test_args(direnv_project: DirenvProject) -> None:
     direnv_project.setup_envrc("use nix --argstr someArg OK")
     direnv_exec(direnv_project, "echo $SHOULD_BE_SET")

tests/testenv/shell.nix

@@ -1,6 +1,9 @@
-{ pkgs ? import <nixpkgs> { }, someArg ? null, shellHook ? ''
+{ pkgs ? import (builtins.getFlake (toString ./.)).inputs.nixpkgs { }
+, someArg ? null
+, shellHook ? ''
   echo "Executing shellHook."
-'' }:
+''
+}:
 pkgs.mkShellNoCC {
   inherit shellHook;