RecursionError when reindexing Dataset with pandas extension arrays inside

[ilia-kats]

What happened?

When trying to reindex a Dataset that contains a Pandas extension array, I get a RecursionError: maximum recursion depth exceeded.

What did you expect to happen?

reindexing succeeds

Minimal Complete Verifiable Example

import xarray as xr
import pandas as pd
series = pd.Series([1, 2, pd.NA, 3], dtype=pd.Int32Dtype())
test = xr.Dataset({"test": series})
test.reindex(dim_0=series.index)

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

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/dataset.py:3571, in Dataset.reindex(self, indexers, method, tolerance, copy, fill_value, **indexers_kwargs)
   3373 """Conform this object onto a new set of indexes, filling in
   3374 missing values with ``fill_value``. The default fill value is NaN.
   3375 
   (...)
   3568 
   3569 """
   3570 indexers = utils.either_dict_or_kwargs(indexers, indexers_kwargs, "reindex")
-> 3571 return alignment.reindex(
   3572     self,
   3573     indexers=indexers,
   3574     method=method,
   3575     tolerance=tolerance,
   3576     copy=copy,
   3577     fill_value=fill_value,
   3578 )

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/structure/alignment.py:1000, in reindex(obj, indexers, method, tolerance, copy, fill_value, sparse, exclude_vars)
    981 # TODO: (benbovy - explicit indexes): uncomment?
    982 # --> from reindex docstrings: "any mismatched dimension is simply ignored"
    983 # bad_keys = [k for k in indexers if k not in obj._indexes and k not in obj.dims]
   (...)
    987 #         "or unindexed dimension in the object to reindex"
    988 #     )
    990 aligner = Aligner(
    991     (obj,),
    992     indexes=indexers,
   (...)
    998     exclude_vars=exclude_vars,
    999 )
-> 1000 aligner.align()
   1001 return aligner.results[0]

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/structure/alignment.py:583, in Aligner.align(self)
    581     self.results = self.objects
    582 else:
--> 583     self.reindex_all()

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/structure/alignment.py:558, in Aligner.reindex_all(self)
    557 def reindex_all(self) -> None:
--> 558     self.results = tuple(
    559         self._reindex_one(obj, matching_indexes)
    560         for obj, matching_indexes in zip(
    561             self.objects, self.objects_matching_indexes, strict=True
    562         )
    563     )

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/structure/alignment.py:559, in <genexpr>(.0)
    557 def reindex_all(self) -> None:
    558     self.results = tuple(
--> 559         self._reindex_one(obj, matching_indexes)
    560         for obj, matching_indexes in zip(
    561             self.objects, self.objects_matching_indexes, strict=True
    562         )
    563     )

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/structure/alignment.py:547, in Aligner._reindex_one(self, obj, matching_indexes)
    544 new_indexes, new_variables = self._get_indexes_and_vars(obj, matching_indexes)
    545 dim_pos_indexers = self._get_dim_pos_indexers(matching_indexes)
--> 547 return obj._reindex_callback(
    548     self,
    549     dim_pos_indexers,
    550     new_variables,
    551     new_indexes,
    552     self.fill_value,
    553     self.exclude_dims,
    554     self.exclude_vars,
    555 )

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/dataset.py:3270, in Dataset._reindex_callback(self, aligner, dim_pos_indexers, variables, indexes, fill_value, exclude_dims, exclude_vars)
   3268         reindexed = self._overwrite_indexes(new_indexes, new_variables)
   3269     else:
-> 3270         reindexed = self.copy(deep=aligner.copy)
   3271 else:
   3272     to_reindex = {
   3273         k: v
   3274         for k, v in self.variables.items()
   3275         if k not in variables and k not in exclude_vars
   3276     }

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/dataset.py:1042, in Dataset.copy(self, deep, data)
    945 def copy(self, deep: bool = False, data: DataVars | None = None) -> Self:
    946     """Returns a copy of this dataset.
    947 
    948     If `deep=True`, a deep copy is made of each of the component variables.
   (...)
   1040     pandas.DataFrame.copy
   1041     """
-> 1042     return self._copy(deep=deep, data=data)

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/dataset.py:1078, in Dataset._copy(self, deep, data, memo)
   1076         variables[k] = index_vars[k]
   1077     else:
-> 1078         variables[k] = v._copy(deep=deep, data=data.get(k), memo=memo)
   1080 attrs = copy.deepcopy(self._attrs, memo) if deep else copy.copy(self._attrs)
   1081 encoding = (
   1082     copy.deepcopy(self._encoding, memo) if deep else copy.copy(self._encoding)
   1083 )

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/variable.py:896, in Variable._copy(self, deep, data, memo)
    893         ndata = indexing.MemoryCachedArray(data_old.array)  # type: ignore[assignment]
    895     if deep:
--> 896         ndata = copy.deepcopy(ndata, memo)
    898 else:
    899     ndata = as_compatible_data(data)

File /usr/lib/python3.11/copy.py:172, in deepcopy(x, memo, _nil)
    170                 y = x
    171             else:
--> 172                 y = _reconstruct(x, memo, *rv)
    174 # If is its own copy, don't memoize.
    175 if y is not x:

File /usr/lib/python3.11/copy.py:272, in _reconstruct(x, memo, func, args, state, listiter, dictiter, deepcopy)
    270 if deep:
    271     state = deepcopy(state, memo)
--> 272 if hasattr(y, '__setstate__'):
    273     y.__setstate__(state)
    274 else:

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/extension_array.py:112, in PandasExtensionArray.__getattr__(self, attr)
    111 def __getattr__(self, attr: str) -> object:
--> 112     return getattr(self.array, attr)

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/extension_array.py:112, in PandasExtensionArray.__getattr__(self, attr)
    111 def __getattr__(self, attr: str) -> object:
--> 112     return getattr(self.array, attr)

    [... skipping similar frames: PandasExtensionArray.__getattr__ at line 112 (2971 times)]

File /data/ilia/envs/famo/lib/python3.11/site-packages/xarray/core/extension_array.py:112, in PandasExtensionArray.__getattr__(self, attr)
    111 def __getattr__(self, attr: str) -> object:
--> 112     return getattr(self.array, attr)

RecursionError: maximum recursion depth exceeded

Anything else we need to know?

No response

Environment

INSTALLED VERSIONS

commit: None
python: 3.11.2 (main, Nov 30 2024, 21:22:50) [GCC 12.2.0]
python-bits: 64
OS: Linux
OS-release: 6.12.12+bpo-amd64
machine: x86_64
processor:
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.14.4
libnetcdf: None

xarray: 2025.3.1
pandas: 2.2.3
numpy: 2.0.2
scipy: 1.14.1
netCDF4: None
pydap: None
h5netcdf: None
h5py: 3.12.1
zarr: 3.0.6
cftime: None
nc_time_axis: None
iris: None
bottleneck: None
dask: 2025.1.0
distributed: 2025.2.0
matplotlib: 3.9.2
cartopy: None
seaborn: 0.13.2
numbagg: None
fsspec: 2024.10.0
cupy: None
pint: None
sparse: 0.16.0
flox: None
numpy_groupies: None
setuptools: 66.1.1
pip: 23.0.1
conda: None
pytest: 8.3.3
mypy: None
IPython: 8.29.0
sphinx: 8.1.3