_indexes of DataArray are not deep copied #3899
Description
In DataArray.copy, the _indexes attributes is not deep copied. After pull request #3840, this causes deleting a coordinate of a copy will also delete that coordinate from the original, even for deep copies.
MCVE Code Sample
a0 = xr.DataArray(
np.array([[1, 2, 3], [4, 5, 6]]),
dims=["y", "x"],
coords={"x": ["a", "b", "c"], "y": [-1, 1]},
)
a1 = a0.copy()
del a1.coords["y"]
xr.tests.assert_identical(a0, a0)The result is:
xarray/testing.py:272: in _assert_internal_invariants
_assert_dataarray_invariants(xarray_obj)
xarray/testing.py:222: in _assert_dataarray_invariants
_assert_indexes_invariants_checks(da._indexes, da._coords, da.dims)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
indexes = {'x': Index(['a', 'b', 'c'], dtype='object', name='x')}, possible_coord_variables = {'x': <xarray.IndexVariable 'x' (x: 3)>
array(['a', 'b', 'c'], dtype='<U1'), 'y': <xarray.IndexVariable 'y' (y: 2)>
array([-1, 1])}
dims = ('y', 'x')
def _assert_indexes_invariants_checks(indexes, possible_coord_variables, dims):
assert isinstance(indexes, dict), indexes
assert all(isinstance(v, pd.Index) for v in indexes.values()), {
k: type(v) for k, v in indexes.items()
}
index_vars = {
k for k, v in possible_coord_variables.items() if isinstance(v, IndexVariable)
}
assert indexes.keys() <= index_vars, (set(indexes), index_vars)
# Note: when we support non-default indexes, these checks should be opt-in
# only!
defaults = default_indexes(possible_coord_variables, dims)
> assert indexes.keys() == defaults.keys(), (set(indexes), set(defaults))
E AssertionError: ({'x'}, {'y', 'x'})
xarray/testing.py:185: AssertionError
Expected Output
The test should pass.
Problem Description
Doing a deep copy should make a copy of everything. Changing a deep copy should not alter the original in any way.