RuntimeError when formatting sparse-backed DataArray in f-string

[khaeru]

What happened?

On upgrading from xarray 2022.3.0 to 2022.6.0, f-string formatting of sparse-backed DataArray raises an exception.

What did you expect to happen?

• Code does not error, or
• A breaking change is listed in the “Breaking changes” section of the docs.

Minimal Complete Verifiable Example

import pandas as pd
import xarray as xr

s = pd.Series(
    range(4),
    index=pd.MultiIndex.from_product([list("ab"), list("cd")]),
)

da = xr.DataArray.from_series(s, sparse=True)

print(f"{da}")

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.

Relevant log output

# xarray 2022.3.0:

<xarray.DataArray (level_0: 2, level_1: 2)>
<COO: shape=(2, 2), dtype=float64, nnz=4, fill_value=nan>                                         
Coordinates:                                     
  * level_0  (level_0) object 'a' 'b'
  * level_1  (level_1) object 'c' 'd'

# xarray 2022.6.0:

Traceback (most recent call last):                                                                
  File "/home/khaeru/bug.py", line 11, in <module>
    print(f"{da}")
  File "/home/khaeru/.local/lib/python3.10/site-packages/xarray/core/common.py", line 168, in __format__                                           
    return self.values.__format__(format_spec)
  File "/home/khaeru/.local/lib/python3.10/site-packages/xarray/core/dataarray.py", line 685, in values                                            
    return self.variable.values
  File "/home/khaeru/.local/lib/python3.10/site-packages/xarray/core/variable.py", line 527, in values                                             
    return _as_array_or_item(self._data)
  File "/home/khaeru/.local/lib/python3.10/site-packages/xarray/core/variable.py", line 267, in _as_array_or_item                                                                                   
    data = np.asarray(data)
  File "/home/khaeru/.local/lib/python3.10/site-packages/sparse/_sparse_array.py", line 229, in __array__                                                                                           
    raise RuntimeError(
RuntimeError: Cannot convert a sparse array to dense automatically. To manually densify, use the todense method.

Anything else we need to know?

Along with the versions below, I have confirmed the error occurs with both sparse 0.12 and sparse 0.13.

Environment

INSTALLED VERSIONS ------------------ commit: None python: 3.10.4 (main, Jun 29 2022, 12:14:53) [GCC 11.2.0] python-bits: 64 OS: Linux OS-release: 5.15.0-41-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_CA.UTF-8 LOCALE: ('en_CA', 'UTF-8') libhdf5: 1.10.7 libnetcdf: 4.8.1

xarray: 2022.6.0
pandas: 1.4.2
numpy: 1.22.4
scipy: 1.8.0
netCDF4: 1.5.8
pydap: None
h5netcdf: 0.12.0
h5py: 3.6.0
Nio: None
zarr: None
cftime: 1.5.2
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: 1.3.2
dask: 2022.01.0+dfsg
distributed: 2022.01.0+ds.1
matplotlib: 3.5.1
cartopy: 0.20.2
seaborn: 0.11.2
numbagg: None
fsspec: 2022.01.0
cupy: None
pint: 0.18
sparse: 0.13.0
flox: None
numpy_groupies: None
setuptools: 62.1.0
pip: 22.0.2
conda: None
pytest: 6.2.5
IPython: 7.31.1
sphinx: 4.5.0

[Illviljan]

This comes from #5981, I think it's better to just let the backend array (numpy, dask, sparse etc.) determine how to handle string formatting instead of forcing to numpy arrays.

[khaeru]

Thanks @Illviljan for the fix! 🙏🏾