Add suggested changes to make apply_ufunc keep attrs

Author: max-sixty

xarray/core/computation.py

@@ -433,6 +433,7 @@ def apply_dict_of_variables_vfunc(
     join="inner",
     fill_value=None,
     on_missing_core_dim: MissingCoreDimOptions = "raise",
+    keep_attrs="override",
 ):
     """Apply a variable level function over dicts of DataArray, DataArray,
     Variable and ndarray objects.
@@ -445,7 +446,7 @@ def apply_dict_of_variables_vfunc(
     for name, variable_args in zip(names, grouped_by_name):
         core_dim_present = _check_core_dims(signature, variable_args, name)
         if core_dim_present is True:
-            result_vars[name] = func(*variable_args)
+            result_vars[name] = func(*variable_args, keep_attrs=keep_attrs)
         else:
             if on_missing_core_dim == "raise":
                 raise ValueError(core_dim_present)
@@ -522,6 +523,7 @@ def apply_dataset_vfunc(
         join=dataset_join,
         fill_value=fill_value,
         on_missing_core_dim=on_missing_core_dim,
+        keep_attrs=keep_attrs,
     )
 
     out: Dataset | tuple[Dataset, ...]

xarray/tests/test_rolling.py

@@ -772,18 +772,13 @@ def test_rolling_exp_keep_attrs(self, ds) -> None:
         # discard attrs
         result = ds.rolling_exp(time=10).mean(keep_attrs=False)
         assert result.attrs == {}
-        # TODO: from #8114 — this arguably should be empty, but `apply_ufunc` doesn't do
-        # that at the moment. We should change in `apply_func` rather than
-        # special-case it here.
-        #
-        # assert result.z1.attrs == {}
+        assert result.z1.attrs == {}
 
         # test discard attrs using global option
         with set_options(keep_attrs=False):
             result = ds.rolling_exp(time=10).mean()
         assert result.attrs == {}
-        # See above
-        # assert result.z1.attrs == {}
+        assert result.z1.attrs == {}
 
         # keyword takes precedence over global option
         with set_options(keep_attrs=False):
@@ -794,8 +789,7 @@ def test_rolling_exp_keep_attrs(self, ds) -> None:
         with set_options(keep_attrs=True):
             result = ds.rolling_exp(time=10).mean(keep_attrs=False)
         assert result.attrs == {}
-        # See above
-        # assert result.z1.attrs == {}
+        assert result.z1.attrs == {}
 
         with pytest.warns(
             UserWarning,