cast numpy scalars to arrays in NamedArray.from_array (#10008)

* check that aggregations result in array objects

* don't consider numpy scalars as arrays

* changelog [skip-ci]

* retrigger CI

* Update xarray/tests/test_namedarray.py

---------

Co-authored-by: Kai Mühlbauer <kmuehlbauer@wradlib.org>

Author: keewis

doc/whats-new.rst

@@ -106,6 +106,8 @@ Bug fixes
   By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_.
 - Fix weighted ``polyfit`` for arrays with more than two dimensions (:issue:`9972`, :pull:`9974`).
   By `Mattia Almansi <https://github.com/malmans2>`_.
+- Cast ``numpy`` scalars to arrays in :py:meth:`NamedArray.from_arrays` (:issue:`10005`, :pull:`10008`)
+  By `Justus Magin <https://github.com/keewis>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/namedarray/core.py

@@ -205,7 +205,7 @@ def from_array(
 
         return NamedArray(dims, data, attrs)
 
-    if isinstance(data, _arrayfunction_or_api):
+    if isinstance(data, _arrayfunction_or_api) and not isinstance(data, np.generic):
         return NamedArray(dims, data, attrs)
 
     if isinstance(data, tuple):

xarray/tests/test_namedarray.py

@@ -591,6 +591,13 @@ def test_warn_on_repeated_dimension_names(self) -> None:
         with pytest.warns(UserWarning, match="Duplicate dimension names"):
             NamedArray(("x", "x"), np.arange(4).reshape(2, 2))
 
+    def test_aggregation(self) -> None:
+        x: NamedArray[Any, np.dtype[np.int64]]
+        x = NamedArray(("x", "y"), np.arange(4).reshape(2, 2))
+
+        result = x.sum()
+        assert isinstance(result.data, np.ndarray)
+
 
 def test_repr() -> None:
     x: NamedArray[Any, np.dtype[np.uint64]]