Fix a bug introduced in #2087 (#2100)

* Bugfix introduced by #2087

* flake8

* Remove trailing whitespaces

Author: fujiisoup

xarray/core/merge.py

@@ -561,7 +561,7 @@ def dataset_update_method(dataset, other):
             coord_names = [c for c in obj.coords
                            if c not in obj.dims and c in dataset.coords]
             if coord_names:
-                other[k] = obj.drop(*coord_names)
+                other[k] = obj.drop(coord_names)
 
     return merge_core([dataset, other], priority_arg=1,
                       indexes=dataset.indexes)

xarray/tests/test_dataset.py

@@ -2366,6 +2366,13 @@ def test_setitem_with_coords(self):
         actual['numbers'] = other
         assert actual['numbers'][0] == 10
 
+        # GH: 2099
+        ds = Dataset({'var': ('x', [1, 2, 3])},
+                     coords={'x': [0, 1, 2], 'z1': ('x', [1, 2, 3]),
+                             'z2': ('x', [1, 2, 3])})
+        ds['var'] = ds['var'] * 2
+        assert np.allclose(ds['var'], [2, 4, 6])
+
     def test_setitem_align_new_indexes(self):
         ds = Dataset({'foo': ('x', [1, 2, 3])}, {'x': [0, 1, 2]})
         ds['bar'] = DataArray([2, 3, 4], [('x', [1, 2, 3])])