Invalidate metadata cache on scene switch

src/ndevio/nimage.py

@@ -146,6 +146,26 @@ def _initialize_source_state(self, image: ImageLike) -> None:
         self.path = source
         self._is_remote = True
 
+    def set_scene(self, scene_id: str | int) -> None:
+        """Switch the operating scene, invalidating cached layer data.
+
+        Extends :meth:`BioImage.set_scene` so that switching scenes clears
+        this image's lazy ``reference_xarray`` / ``layer_data`` /
+        ``_layer_metadata`` caches, which are scene-specific.  Callers (scene
+        widget, reader's open-all-scenes path) get correct reload behaviour
+        without reaching into privates.
+
+        Parameters
+        ----------
+        scene_id : str | int
+            The scene id (string) or scene index (integer) to switch to.
+
+        """
+        super().set_scene(scene_id)
+        self._reference_xarray = None
+        self._layer_data = None
+        self._layer_metadata = None
+
     def _fits_in_memory(self) -> bool:
         """Return True if the uncompressed image fits comfortably in RAM."""
         if self.path is None:

src/ndevio/widgets/_scene_widget.py

@@ -114,10 +114,6 @@ def open_scene(self) -> None:
             scene_index = int(scene.split(DELIMITER)[0])
             self.img.set_scene(scene_index)
 
-            # Clear cached data so new scene is loaded
-            self.img._reference_xarray = None
-            self.img._layer_data = None
-
             # Get layer tuples and add to viewer using napari's Layer.create()
             from napari.layers import Layer
 

tests/test_nimage.py

@@ -514,6 +514,36 @@ def test_colormap_three_plus_channels_uses_multi_channel_cycle(
         assert colormaps[2] == MULTI_CHANNEL_CYCLE[2]  # yellow
         assert colormaps[3] == MULTI_CHANNEL_CYCLE[3]  # blue
 
+
+def test_set_scene_invalidates_cached_layer_data(resources_dir: Path):
+    """Switching scenes clears the lazy reference_xarray / layer_data caches.
+
+    Regression test: the scene widget previously had to clear these privates
+    by hand, and the reader's open-all-scenes path never did — returning
+    stale scene-0 data for every scene. ``set_scene`` now owns the
+    invalidation so every caller reloads the new scene.
+    """
+    img = nImage(resources_dir / CZI_FILE)
+    assert len(img.scenes) > 1
+
+    # Prime the caches on the current scene
+    img.get_layer_data_tuples()
+    assert img._reference_xarray is not None
+    assert img._layer_data is not None
+    assert img._layer_metadata is not None
+
+    img.set_scene(1)
+
+    # Caches must be invalidated so the next access reloads the new scene
+    assert img._reference_xarray is None
+    assert img._layer_data is None
+    assert img._layer_metadata is None
+
+    # And data reloads lazily for the new scene
+    assert img.reference_xarray is not None
+    assert img.layer_scale is not None
+    assert img._layer_metadata is not None
+
     def test_auto_detect_labels_from_channel_name(self, resources_dir: Path):
         """Test that channels with label-like names are detected as labels."""
         import numpy as np