cumsum drops coordinate in Dataset but not DataArray

[delgadom]

What happened?

Inconsistent behavior between cumulative sum on Dataset and DataArrray - Dataset.cumsum drops coordinate along reduction dim (even though cumsum is not actually a reduction).

DataArray does not do this. The dimension is still there, but as a dimension without a coordinate.

What did you expect to happen?

Expected Dataset to behave like DataArray, without dropping the coordinate.

Minimal Complete Verifiable Example

import xarray as xr

ds = xr.Dataset({"var1": (('dim1', ), [0, 1, 2])}, coords={"dim1": ['a', 'b', 'c']})
print(ds)

print("\n\nDataset cumsum:\n")
print(ds.cumsum(dim="dim1"))

print("\n\nDataArray cumsum:\n")
print(ds["var1"].cumsum(dim="dim1"))

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

<xarray.Dataset> Size: 36B
Dimensions:  (dim1: 3)
Coordinates:
  * dim1     (dim1) <U1 12B 'a' 'b' 'c'
Data variables:
    var1     (dim1) int64 24B 0 1 2


Dataset cumsum:

<xarray.Dataset> Size: 24B
Dimensions:  (dim1: 3)
Dimensions without coordinates: dim1
Data variables:
    var1     (dim1) int64 24B 0 1 3


DataArray cumsum:

<xarray.DataArray 'var1' (dim1: 3)> Size: 24B
array([0, 1, 3])
Coordinates:
  * dim1     (dim1) <U1 12B 'a' 'b' 'c'

Anything else we need to know?

No response

Environment

INSTALLED VERSIONS

commit: None
python: 3.11.4 | packaged by conda-forge | (main, Jun 10 2023, 18:08:41) [Clang 15.0.7 ]
python-bits: 64
OS: Darwin
OS-release: 24.0.0
machine: arm64
processor: arm
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.14.0
libnetcdf: 4.9.2

xarray: 2024.10.0
pandas: 2.2.3
numpy: 1.24.3
scipy: 1.14.1
netCDF4: 1.6.4
pydap: None
h5netcdf: None
h5py: 3.8.0
zarr: 2.18.3
cftime: 1.6.2
nc_time_axis: None
iris: None
bottleneck: 1.3.7
dask: 2024.8.0
distributed: 2024.8.0
matplotlib: 3.7.1
cartopy: 0.24.0
seaborn: 0.12.2
numbagg: None
fsspec: 2023.6.0
cupy: None
pint: None
sparse: None
flox: 9.11
numpy_groupies: 0.11.2
setuptools: 67.7.2
pip: 23.1.2
conda: None
pytest: None
mypy: None
IPython: 8.14.0
sphinx: None

[dcherian]

Dupe of #6528