Fix xr.where(..., keep_attrs=True) bug (#6461)

* check for attrs on x

* ensure we only get attrs of x

* add whats-new

doc/whats-new.rst

@@ -76,6 +76,8 @@ Bug fixes
 - In the API for backends, support dimensions that express their preferred chunk sizes
   as a tuple of integers. (:issue:`6333`, :pull:`6334`)
   By `Stan West <https://github.com/stanwest>`_.
+- Fix bug in :py:func:`where` when passing non-xarray objects with ``keep_attrs=True``. (:issue:`6444`, :pull:`6461`)
+  By `Sam Levang <https://github.com/slevang>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/core/computation.py

@@ -1825,11 +1825,10 @@ def where(cond, x, y, keep_attrs=None):
     """
     if keep_attrs is None:
         keep_attrs = _get_keep_attrs(default=False)
-
     if keep_attrs is True:
         # keep the attributes of x, the second parameter, by default to
         # be consistent with the `where` method of `DataArray` and `Dataset`
-        keep_attrs = lambda attrs, context: attrs[1]
+        keep_attrs = lambda attrs, context: getattr(x, "attrs", {})
 
     # alignment for three arguments is complicated, so don't support it yet
     return apply_ufunc(

xarray/tests/test_computation.py

@@ -1928,6 +1928,10 @@ def test_where_attrs() -> None:
     expected = xr.DataArray([1, 0], dims="x", attrs={"attr": "x"})
     assert_identical(expected, actual)
 
+    # ensure keep_attrs can handle scalar values
+    actual = xr.where(cond, 1, 0, keep_attrs=True)
+    assert actual.attrs == {}
+
 
 @pytest.mark.parametrize("use_dask", [True, False])
 @pytest.mark.parametrize("use_datetime", [True, False])