Follow keep_attrs in Dataset binary ops (#7391)

* honor keep_attrs option durig Dataset binary ops

* add test for Dataset binary ops keep_attrs

* fix mypy assignment error

* Apply suggestions from code review

accept non-boolean keep_attrs arguments

Co-authored-by: Justus Magin <keewis@users.noreply.github.com>

* test all cases for binary_ops keep_attrs

* fix import

* add keep_attrs bugfix to whats-new.rst

* accept only boolean keep_attrs in binary_ops

* Update whats-new.rst

Co-authored-by: Justus Magin <keewis@users.noreply.github.com>
Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

Author: 3 people

doc/whats-new.rst

@@ -53,6 +53,8 @@ Bug fixes
 - :py:func:`xarray.concat` can now concatenate variables present in some datasets but
   not others (:issue:`508`, :pull:`7400`).
   By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_ and `Scott Chamberlin <https://github.com/scottcha>`_.
+- Handle ``keep_attrs`` option in binary operators of :py:meth:`Dataset` (:issue:`7390`, :pull:`7391`).
+  By `Aron Gergely <https://github.com/arongergely>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/core/dataset.py

@@ -6585,6 +6585,9 @@ def _binary_op(self, other, f, reflexive=False, join=None) -> Dataset:
             self, other = align(self, other, join=align_type, copy=False)  # type: ignore[assignment]
         g = f if not reflexive else lambda x, y: f(y, x)
         ds = self._calculate_binary_op(g, other, join=align_type)
+        keep_attrs = _get_keep_attrs(default=False)
+        if keep_attrs:
+            ds.attrs = self.attrs
         return ds
 
     def _inplace_binary_op(self: T_Dataset, other, f) -> T_Dataset:

xarray/tests/test_dataset.py

@@ -5850,6 +5850,21 @@ def test_binary_op_join_setting(self) -> None:
             actual = ds1 + ds2
             assert_equal(actual, expected)
 
+    @pytest.mark.parametrize(
+        ["keep_attrs", "expected"],
+        (
+            pytest.param(False, {}, id="False"),
+            pytest.param(True, {"foo": "a", "bar": "b"}, id="True"),
+        ),
+    )
+    def test_binary_ops_keep_attrs(self, keep_attrs, expected) -> None:
+        ds1 = xr.Dataset({"a": 1}, attrs={"foo": "a", "bar": "b"})
+        ds2 = xr.Dataset({"a": 1}, attrs={"foo": "a", "baz": "c"})
+        with xr.set_options(keep_attrs=keep_attrs):
+            ds_result = ds1 + ds2
+
+        assert ds_result.attrs == expected
+
     def test_full_like(self) -> None:
         # For more thorough tests, see test_variable.py
         # Note: testing data_vars with mismatched dtypes