allow all np.ndarray subclasses

Author: slevang

xarray/core/variable.py

@@ -321,17 +321,15 @@ def convert_non_numpy_type(data):
         else:
             data = np.asarray(data)
 
-    _is_array_like = isinstance(data, np.ndarray | np.generic)
-    _is_nep18 = hasattr(data, "__array_function__")
-    _has_array_api = hasattr(data, "__array_namespace__")
-    _has_unit = hasattr(data, "_unit")
-
-    # Allow `astropy.units.Quantity`
-    if _is_array_like and (_is_nep18 or _has_array_api) and _has_unit:
-        return cast("T_DuckArray", data)
-
-    # immediately return array-like types except `numpy.ndarray` subclasses and `numpy` scalars
-    if not _is_array_like and (_is_nep18 or _has_array_api):
+    if isinstance(data, np.matrix):
+        data = np.asarray(data)
+
+    # immediately return array-like types except `numpy.ndarray` and `numpy` scalars
+    # compare types with `is` instead of `isinstance` to allow `numpy.ndarray` subclasses
+    is_numpy = type(data) is np.ndarray or isinstance(data, np.generic)
+    if not is_numpy and (
+        hasattr(data, "__array_function__") or hasattr(data, "__array_namespace__")
+    ):
         return cast("T_DuckArray", data)
 
     # validate whether the data is valid data types. Also, explicitly cast `numpy`

xarray/tests/test_variable.py

@@ -2746,6 +2746,19 @@ def test_ones_like(self) -> None:
         assert_identical(ones_like(orig), full_like(orig, 1))
         assert_identical(ones_like(orig, dtype=int), full_like(orig, 1, dtype=int))
 
+    def test_numpy_ndarray_subclass(self):
+        class SubclassedArray(np.ndarray):
+            def __new__(cls, array, foo):
+                obj = np.asarray(array).view(cls)
+                obj.foo = foo
+                return obj
+
+        data = SubclassedArray([1, 2, 3], foo="bar")
+        actual = as_compatible_data(data)
+        assert isinstance(actual, SubclassedArray)
+        assert actual.foo == "bar"
+        assert_array_equal(data, actual)
+
     def test_unsupported_type(self):
         # Non indexable type
         class CustomArray(NDArrayMixin):