nix-required-mounts: handle __structuredAttrs

nixos/tests/nix-required-mounts/default.nix

@@ -14,7 +14,8 @@ in
     system.extraDependencies = [ (pkgs.runCommand "deps" { } "mkdir $out").inputDerivation ];
     nix.nixPath = [ "nixpkgs=${../../..}" ];
     nix.settings.substituters = lib.mkForce [ ];
-    nix.settings.system-features = [ "supported-feature" ]; nix.settings.experimental-features = [ "nix-command" ];
+    nix.settings.system-features = [ "supported-feature" ];
+    nix.settings.experimental-features = [ "nix-command" ];
     programs.nix-required-mounts.enable = true;
     programs.nix-required-mounts.allowedPatterns.supported-feature = {
       onFeatures = [ "supported-feature" ];
@@ -40,5 +41,7 @@ in
     person_do("nix-build ${./ensure-path-not-present.nix} --argstr feature supported-feature")
     person_do("nix-build ${./test-require-feature.nix} --argstr feature supported-feature")
     person_do("nix-build ${./test-require-feature.nix} --argstr feature unsupported-feature", succeed=False)
+    person_do("nix-build ${./test-structured-attrs.nix} --argstr feature supported-feature")
+    person_do("nix-build ${./test-structured-attrs-empty.nix}")
   '';
 }

nixos/tests/nix-required-mounts/test-structured-attrs-empty.nix

@@ -0,0 +1,10 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+pkgs.runCommandNoCC "nix-required-mounts-structured-attrs-no-features"
+{
+  __structuredAttrs = true;
+} ''
+  touch $out
+''
+
+

nixos/tests/nix-required-mounts/test-structured-attrs.nix

@@ -0,0 +1,15 @@
+{ pkgs ? import <nixpkgs> { }, feature }:
+
+pkgs.runCommandNoCC "${feature}-present-structured"
+{
+  __structuredAttrs = true;
+  requiredSystemFeatures = [ feature ];
+} ''
+  if [[ -e /${feature}-files ]]; then
+    touch $out
+  else
+    echo "The host declares ${feature} support, but doesn't expose /${feature}-files" >&2
+    echo "Do we fail to parse __structuredAttrs=true derivations?" >&2
+  fi
+''
+

pkgs/by-name/ni/nix-required-mounts/main.py

@@ -47,6 +47,13 @@ def symlink_parents(p: Path) -> List[Path]:
     return out
 
 
+def get_strings(drv_env: dict, name: str) -> List[str]:
+    if "__json" in drv_env:
+        return list(json.loads(drv_env["__json"]).get(name, []))
+    else:
+        return drv_env.get(name, "").split()
+
+
 def entrypoint():
     args = parser.parse_args()
     drv_path = args.derivation_path
@@ -71,7 +78,7 @@ def entrypoint():
         capture_output=True,
     )
     try:
-        drv = json.loads(proc.stdout)
+        parsed_drv = json.loads(proc.stdout)
     except json.JSONDecodeError:
         print(
             "[E] Couldn't parse the output of"
@@ -85,7 +92,7 @@ def entrypoint():
         )
         print("[I] Exiting the nix-required-binds hook", file=stderr)
         return
-    [canon_drv_path] = drv.keys()
+    [canon_drv_path] = parsed_drv.keys()
 
     allowed_patterns = config["allowedPatterns"]
     known_features = set(
@@ -94,11 +101,9 @@ def entrypoint():
         )
     )
 
-    drv_env = drv[canon_drv_path].get("env", {})
-    features = drv_env.get("requiredSystemFeatures", [])
-    if isinstance(features, str):
-        features = features.split()
-
+    parsed_drv = parsed_drv[canon_drv_path]
+    drv_env = parsed_drv.get("env", {})
+    features = get_strings(drv_env, "requiredSystemFeatures")
     features = list(filter(known_features.__contains__, features))
 
     patterns = list(