Prevent edge cases in XArrayInterface from crashing (#5809)

holoviews/core/data/xarray.py

@@ -144,7 +144,7 @@ def retrieve_unit_and_label(dim):
                     packed = True
                 else:
                     data = {d: v for d, v in zip(dimensions, data)}
-            elif isinstance(data, list) and data == []:
+            elif isinstance(data, (list, np.ndarray)) and len(data) == 0:
                 dimensions = [d.name for d in kdims + vdims]
                 data = {d: np.array([]) for d in dimensions[:ndims]}
                 data.update({d: np.empty((0,) * ndims) for d in dimensions[ndims:]})

holoviews/core/sheetcoords.py

@@ -517,7 +517,6 @@ def _boundsspec2slicespec(boundsspec,scs):
 
         l_idx = int(np.ceil(l_m-0.5))
         t_idx = int(np.ceil(t_m-0.5))
-        # CBENHANCEMENT: Python 2.6's math.trunc()?
         r_idx = int(np.floor(r_m+0.5))
         b_idx = int(np.floor(b_m+0.5))
 

holoviews/tests/core/data/test_xarrayinterface.py

@@ -11,7 +11,7 @@
 except ImportError:
     raise SkipTest("Could not import xarray, skipping XArrayInterface tests.")
 
-from holoviews.core.data import Dataset, concat
+from holoviews.core.data import Dataset, concat, XArrayInterface
 from holoviews.core.dimension import Dimension
 from holoviews.core.spaces import HoloMap
 from holoviews.element import Image, RGB, HSV, QuadMesh
@@ -258,6 +258,18 @@ def test_mask_2d_array_transposed(self):
         expected[mask] = np.nan
         self.assertEqual(masked_array, expected)
 
+    def test_from_empty_numpy(self):
+        """
+        Datashader sometimes pass an empty array to the interface
+        """
+        kdims = ["dim_0", "dim_1"]
+        vdims = ["dim_2"]
+        ds = XArrayInterface.init(Image, np.array([]), kdims, vdims)
+        assert isinstance(ds[0], xr.Dataset)
+        assert ds[0][vdims[0]].size == 0
+        assert ds[1]["kdims"] == kdims
+        assert ds[1]["vdims"] == vdims
+
     # Disabled tests for NotImplemented methods
     def test_dataset_array_init_hm(self):
         "Tests support for arrays (homogeneous)"