What happened?

Sometimes I store info about coordinates in the attributes on the coordinate. It's useful for stuff like units or resolutions.
I noticed that these attributes can go missing from DataArrays that are used as the input to xr.where, which is a somewhat unexpected side-effect.

What did you expect to happen?

The input DataArray is left unmodified by xr.where.

Minimal Complete Verifiable Example

import xarray as xr
import numpy as np

values = xr.DataArray(np.linspace(0, 2), dims='x')
values = values.assign_coords(x=values.x.assign_attrs(attr=10))
print('attr' in values.x.attrs)  # True
nonzero = values != 0
print('attr' in values.x.attrs)  # True
xr.where(nonzero, values, np.nan, keep_attrs=False)
print('attr' in values.x.attrs)  # False

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

No response

Anything else we need to know?

No response

Environment