Fix stateful-sensor crash on GetStatus; add explicit Status API

resources/statefulsensor/statefulsensor.go

@@ -49,7 +49,6 @@ type statefulSensor struct {
 	resource.AlwaysRebuild
 	resource.Named
 
-	name   resource.Name
 	logger logging.Logger
 	cfg    *Config
 
@@ -91,7 +90,7 @@ func New(ctx context.Context, deps resource.Dependencies, name resource.Name, co
 	}
 
 	s := &statefulSensor{
-		name:       name,
+		Named:      name.AsNamed(),
 		logger:     logger,
 		cfg:        conf,
 		filePath:   filePath,
@@ -169,10 +168,6 @@ func (s *statefulSensor) saveToFile() error {
 	return nil
 }
 
-func (s *statefulSensor) Name() resource.Name {
-	return s.name
-}
-
 func (s *statefulSensor) Readings(ctx context.Context, extra map[string]interface{}) (map[string]interface{}, error) {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
@@ -185,6 +180,22 @@ func (s *statefulSensor) Readings(ctx context.Context, extra map[string]interfac
 	return readings, nil
 }
 
+// Status reports operational metadata for the sensor, served via the sensor
+// service's GetStatus RPC. It is defined explicitly (rather than relying on the
+// empty default promoted from the embedded resource.Named) so the model both
+// exposes useful state and is guaranteed to have a non-nil receiver. Unlike
+// Readings, which returns the stored value itself, Status reports where the
+// value is persisted and how many keys it holds.
+func (s *statefulSensor) Status(ctx context.Context) (map[string]interface{}, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	return map[string]interface{}{
+		"file_path": s.filePath,
+		"num_keys":  len(s.value),
+	}, nil
+}
+
 // DoCommand supports a "set" command that replaces the value the sensor holds.
 //
 // Example:

resources/statefulsensor/statefulsensor_test.go

@@ -93,6 +93,40 @@ func TestDefaultPathUsesModuleDataDir(t *testing.T) {
 	}
 }
 
+// TestStatus verifies the explicit Status API. It also guards against a
+// regression where the embedded resource.Named was left uninitialized: the
+// sensor service's GetStatus RPC calls Status on the resource, and with a nil
+// embedded Named the promoted default Status dereferenced a nil receiver and
+// crashed the module (SIGSEGV).
+func TestStatus(t *testing.T) {
+	ctx := context.Background()
+	path := filepath.Join(t.TempDir(), "state.json")
+	s := newTestSensor(t, path)
+
+	status, err := s.Status(ctx)
+	if err != nil {
+		t.Fatalf("Status: %v", err)
+	}
+	if status["file_path"] != path {
+		t.Fatalf("Status file_path = %v, want %q", status["file_path"], path)
+	}
+	if status["num_keys"] != 0 {
+		t.Fatalf("Status num_keys = %v, want 0", status["num_keys"])
+	}
+
+	if _, err := s.DoCommand(ctx, map[string]interface{}{"set": map[string]interface{}{"a": 1.0, "b": 2.0}}); err != nil {
+		t.Fatalf("DoCommand set: %v", err)
+	}
+
+	status, err = s.Status(ctx)
+	if err != nil {
+		t.Fatalf("Status after set: %v", err)
+	}
+	if status["num_keys"] != 2 {
+		t.Fatalf("Status num_keys = %v, want 2", status["num_keys"])
+	}
+}
+
 func TestDoCommandRejectsUnknownCommand(t *testing.T) {
 	ctx := context.Background()
 	s := newTestSensor(t, filepath.Join(t.TempDir(), "state.json"))