Fixing data_setitem function of label layer (#6618)

Labels layer bug fix. Adapting the test now

# References and relevant issues
This PR closes an new issue that hasn't been noticed yet.

# Description
This fixes a bug. The following error arises if the "value" input is an
array and there are unchanged values in the indices.
*** ValueError: shape mismatch: value array of shape (855416,) could not
be broadcast to indexing result of shape (88060,)

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

napari/layers/labels/_tests/test_labels.py

@@ -701,7 +701,8 @@ def test_data_setitem_multi_dim():
     data = zarr.zeros((10, 10, 10), chunks=(5, 5, 5), dtype=np.uint32)
     labels = Labels(data)
     labels.data_setitem(
-        (np.array([0, 1]), np.array([1, 1]), np.array([0, 0])), [1, 2]
+        (np.array([0, 1, 1]), np.array([1, 1, 2]), np.array([0, 0, 0])),
+        [1, 2, 0],
     )
 
 

napari/layers/labels/labels.py

@@ -1578,6 +1578,10 @@ def data_setitem(self, indices, value, refresh=True):
         else:
             value = self._slice.image.raw.dtype.type(value)
 
+        # Resize value array to remove unchanged elements
+        if isinstance(value, np.ndarray):
+            value = value[changed_indices]
+
         if not indices or indices[0].size == 0:
             return