Allow selecting variables using a list with mixed data types (pydata#…

…5394)

* force object dtype in asarray

* remove asarray

xarray/core/dataset.py

@@ -1487,7 +1487,7 @@ def __getitem__(self, key):
         if hashable(key):
             return self._construct_dataarray(key)
         else:
-            return self._copy_listed(np.asarray(key))
+            return self._copy_listed(key)
 
     def __setitem__(self, key: Union[Hashable, List[Hashable], Mapping], value) -> None:
         """Add an array to this dataset.

xarray/tests/test_dataset.py

@@ -3305,6 +3305,11 @@ def test_getitem_hashable(self):
         with pytest.raises(KeyError, match=r"('var1', 'var2')"):
             data[("var1", "var2")]
 
+    def test_getitem_multiple_dtype(self):
+        keys = ["foo", 1]
+        dataset = Dataset({key: ("dim0", range(1)) for key in keys})
+        assert_identical(dataset, dataset[keys])
+
     def test_virtual_variables_default_coords(self):
         dataset = Dataset({"foo": ("x", range(10))})
         expected = DataArray(range(10), dims="x", name="x")