remove datetime tests with pint (#3788)

* don't try to wrap datetime objects in pint

* make sure we actually decide based on dask.array.Array

* update whats-new.rst

* directly use isnat

* always use numpy's isnat

Author: keewis

doc/whats-new.rst

@@ -58,6 +58,8 @@ Internal Changes
 - Removed the internal ``import_seaborn`` function which handled the deprecation of
   the ``seaborn.apionly`` entry point (:issue:`3747`).
   By `Mathias Hauser <https://github.com/mathause>`_.
+- Don't test pint integration in combination with datetime objects. (:issue:`3778`, :pull:`3788`)
+  By `Justus Magin <https://github.com/keewis>`_.
 - Changed test_open_mfdataset_list_attr to only run with dask installed
   (:issue:`3777`, :pull:`3780`).
   By `Bruno Pagani <https://github.com/ArchangeGabriel>`_.

xarray/core/duck_array_ops.py

@@ -71,14 +71,7 @@ def fail_on_dask_array_input(values, msg=None, func_name=None):
 isclose = _dask_or_eager_func("isclose")
 
 
-if hasattr(np, "isnat") and (
-    dask_array is None or hasattr(dask_array_type, "__array_ufunc__")
-):
-    # np.isnat is available since NumPy 1.13, so __array_ufunc__ is always
-    # supported.
-    isnat = np.isnat
-else:
-    isnat = _dask_or_eager_func("isnull", eager_module=pd)
+isnat = np.isnat
 isnan = _dask_or_eager_func("isnan")
 zeros_like = _dask_or_eager_func("zeros_like")
 

xarray/tests/test_units.py

@@ -1335,6 +1335,7 @@ def wrapper(cls):
     "test_index_0d_datetime",
     "test_index_0d_timedelta64",
     "test_0d_time_data",
+    "test_index_0d_not_a_time",
     "test_datetime64_conversion",
     "test_timedelta64_conversion",
     "test_pandas_period_index",
@@ -1357,6 +1358,15 @@ def cls(dims, data, *args, **kwargs):
             dims, unit_registry.Quantity(data, unit_registry.m), *args, **kwargs
         )
 
+    def example_1d_objects(self):
+        for data in [
+            range(3),
+            0.5 * np.arange(3),
+            0.5 * np.arange(3, dtype=np.float32),
+            np.array(["a", "b", "c"], dtype=object),
+        ]:
+            yield (self.cls("x", data), data)
+
     @pytest.mark.parametrize(
         "func",
         (