FIX Preserve the shape of empty object arrays

docs/changes.rst

@@ -11,6 +11,8 @@ skops Changelog
 
 v0.17
 -----
+- Fix loading empty NumPy object arrays: the recorded shape is preserved even
+  when a zero-length axis hides later dimensions from the nested list.
 - Fix ``skops update`` failing when a relative output path contains a
   directory, including updates with ``--inplace``.
 - Loading a skops file now checks that each part of the file holds the kind

skops/io/_numpy.py

@@ -110,6 +110,9 @@ def _construct(self):
             shape = self.shape.construct()
             tmp = [o.construct() for o in self.items]
 
+            if 0 in shape:
+                return np.empty(shape, dtype="O")
+
             # TODO: this is a hack to get the correct shape of the array. We
             # should find _a better way_ to do this.
             if len(shape) == 1:

skops/io/tests/test_persist.py

@@ -789,6 +789,25 @@ def test_numpy_object_dtype_2d_array(transpose):
     assert_params_equal(est.__dict__, loaded.__dict__)
 
 
+@pytest.mark.parametrize(
+    "shape", [(0,), (0, 3), (2, 0), (2, 0, 3), (2, 3, 0), (0, 2, 3), (2, 3)]
+)
+@pytest.mark.parametrize("use_file", [False, True])
+def test_numpy_object_dtype_empty_array(shape, use_file, tmp_path):
+    arr = np.full(shape, "value", dtype=object)
+
+    if use_file:
+        path = tmp_path / "array.skops"
+        dump(arr, path)
+        loaded = load(path)
+    else:
+        loaded = loads(dumps(arr))
+
+    assert loaded.shape == shape
+    assert loaded.dtype == arr.dtype
+    np.testing.assert_array_equal(loaded, arr)
+
+
 def test_metainfo():
     class MyEstimator(BaseEstimator):
         """Estimator with attributes of different supported types"""