Add constant ‘nixPath’

It contains the Nix expression search path as a list of { prefix, path
} sets, e.g.

  [ { path = "/nix/var/nix/profiles/per-user/root/channels/nixos"; prefix = ""; }
    { path = "/etc/nixos/configuration.nix"; prefix = "nixos-config"; }
    { path = "/home/eelco/Dev/nix/inst/share/nix/corepkgs"; prefix = "nix"; }
  ]

2 files changed, 9 insertions, 2 deletions

diff --git a/tests/lang.sh b/tests/lang.sh
index bb3b9ca775c3..7157a68c5ceb 100644
--- a/tests/lang.sh
+++ b/tests/lang.sh
@@ -46,7 +46,7 @@ for i in lang/eval-okay-*.nix; do
         if test -e lang/$i.flags; then
             flags=$(cat lang/$i.flags)
         fi
-        if ! NIX_PATH=lang/dir3:lang/dir4_PATH nix-instantiate $flags --eval --strict lang/$i.nix > lang/$i.out; then
+        if ! NIX_PATH=lang/dir3:lang/dir4 nix-instantiate $flags --eval --strict lang/$i.nix > lang/$i.out; then
             echo "FAIL: $i should evaluate"
             fail=1
         elif ! diff lang/$i.out lang/$i.exp; then
diff --git a/tests/lang/eval-okay-search-path.nix b/tests/lang/eval-okay-search-path.nix
index 9b711502336b..c9ea768a417d 100644
--- a/tests/lang/eval-okay-search-path.nix
+++ b/tests/lang/eval-okay-search-path.nix
@@ -1,3 +1,10 @@
-assert builtins.pathExists <nix/buildenv.nix>;
+with import ./lib.nix;
+with builtins;
+
+assert pathExists <nix/buildenv.nix>;
+
+assert length nixPath == 3;
+assert length (filter (x: x.prefix == "nix") nixPath) == 1;
+assert length (filter (x: baseNameOf x.path == "dir4") nixPath) == 1;
 
 import <a.nix> + import <b.nix> + import <c.nix> + import <dir5/c.nix>