tests: add a test for command line ordering

tests/functional/shell-hello.nix

@@ -23,4 +23,20 @@ with import ./config.nix;
         chmod +x $dev/bin/hello2
       '';
   };
+
+  salve-mundi = mkDerivation {
+    name = "salve-mundi";
+    outputs = [ "out" ];
+    meta.outputsToInstall = [ "out" ];
+    buildCommand =
+      ''
+        mkdir -p $out/bin
+
+        cat > $out/bin/hello <<EOF
+        #! ${shell}
+        echo "Salve Mundi from $out/bin/hello"
+        EOF
+        chmod +x $out/bin/hello
+      '';
+  };
 }

tests/functional/shell.sh

@@ -10,6 +10,14 @@ nix shell -f shell-hello.nix hello -c hello NixOS | grep 'Hello NixOS'
 nix shell -f shell-hello.nix hello^dev -c hello2 | grep 'Hello2'
 nix shell -f shell-hello.nix 'hello^*' -c hello2 | grep 'Hello2'
 
+
+if isDaemonNewer "2.20.0pre20231220"; then
+    # Test that command line attribute ordering is reflected in the PATH
+    # https://github.com/NixOS/nix/issues/7905
+    nix shell -f shell-hello.nix hello salve-mundi -c hello | grep 'Hello World'
+    nix shell -f shell-hello.nix salve-mundi hello -c hello | grep 'Salve Mundi'
+fi
+
 requireSandboxSupport
 
 chmod -R u+w $TEST_ROOT/store0 || true