(fix): extension array indexers

xarray/core/dataarray.py

@@ -6873,7 +6873,7 @@ def groupby(
                [[nan, nan, nan],
                 [ 3.,  4.,  5.]]])
         Coordinates:
-          * x_bins   (x_bins) object 16B (5, 15] (15, 25]
+          * x_bins   (x_bins) interval[int64, right] 16B (5, 15] (15, 25]
           * letters  (letters) object 16B 'a' 'b'
         Dimensions without coordinates: y
 

xarray/core/dataset.py

@@ -10517,7 +10517,7 @@ def groupby(
         <xarray.Dataset> Size: 128B
         Dimensions:  (y: 3, x_bins: 2, letters: 2)
         Coordinates:
-          * x_bins   (x_bins) object 16B (5, 15] (15, 25]
+          * x_bins   (x_bins) interval[int64, right] 16B (5, 15] (15, 25]
           * letters  (letters) object 16B 'a' 'b'
         Dimensions without coordinates: y
         Data variables:

xarray/core/indexes.py

@@ -598,7 +598,10 @@ def __init__(
         self.index = index
         self.dim = dim
 
-        if coord_dtype is None:
+        if pd.api.types.is_extension_array_dtype(index.dtype):
+            cast(pd.api.extensions.ExtensionDtype, index.dtype)
+            coord_dtype = index.dtype
+        elif coord_dtype is None:
             coord_dtype = get_valid_numpy_dtype(index)
         self.coord_dtype = coord_dtype
 
@@ -695,6 +698,8 @@ def concat(
 
         if not indexes:
             coord_dtype = None
+        elif len(set(idx.coord_dtype for idx in indexes)) == 1:
+            coord_dtype = indexes[0].coord_dtype
         else:
             coord_dtype = np.result_type(*[idx.coord_dtype for idx in indexes])
 

xarray/core/indexing.py

@@ -10,10 +10,11 @@
 from dataclasses import dataclass, field
 from datetime import timedelta
 from html import escape
-from typing import TYPE_CHECKING, Any, overload
+from typing import TYPE_CHECKING, Any, cast, overload
 
 import numpy as np
 import pandas as pd
+from numpy.typing import DTypeLike
 from packaging.version import Version
 
 from xarray.core import duck_array_ops
@@ -33,8 +34,6 @@
 from xarray.namedarray.pycompat import array_type, integer_types, is_chunked_array
 
 if TYPE_CHECKING:
-    from numpy.typing import DTypeLike
-
     from xarray.core.indexes import Index
     from xarray.core.types import Self
     from xarray.core.variable import Variable
@@ -1707,27 +1706,44 @@ class PandasIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
     __slots__ = ("_dtype", "array")
 
     array: pd.Index
-    _dtype: np.dtype
+    _dtype: np.dtype | pd.api.extensions.ExtensionDtype
 
-    def __init__(self, array: pd.Index, dtype: DTypeLike = None):
+    def __init__(
+        self,
+        array: pd.Index,
+        dtype: DTypeLike | pd.api.extensions.ExtensionDtype | None = None,
+    ):
         from xarray.core.indexes import safe_cast_to_index
 
         self.array = safe_cast_to_index(array)
 
         if dtype is None:
-            self._dtype = get_valid_numpy_dtype(array)
+            if pd.api.types.is_extension_array_dtype(array.dtype):
+                cast(pd.api.extensions.ExtensionDtype, array.dtype)
+                self._dtype = array.dtype
+            else:
+                self._dtype = get_valid_numpy_dtype(array)
+        elif pd.api.types.is_extension_array_dtype(dtype):
+            self._dtype = cast(pd.api.extensions.ExtensionDtype, dtype)
         else:
-            self._dtype = np.dtype(dtype)
+            self._dtype = np.dtype(cast(DTypeLike, dtype))
 
     @property
-    def dtype(self) -> np.dtype:
+    def dtype(self) -> np.dtype | pd.api.extensions.ExtensionDtype:  # type: ignore[override]
         return self._dtype
 
     def __array__(
-        self, dtype: np.typing.DTypeLike = None, /, *, copy: bool | None = None
+        self,
+        dtype: np.typing.DTypeLike | pd.api.extensions.ExtensionDtype | None = None,
+        /,
+        *,
+        copy: bool | None = None,
     ) -> np.ndarray:
         if dtype is None:
             dtype = self.dtype
+        if pd.api.types.is_extension_array_dtype(dtype):
+            dtype = get_valid_numpy_dtype(self.array)
+        dtype = cast(np.dtype, dtype)
         array = self.array
         if isinstance(array, pd.PeriodIndex):
             with suppress(AttributeError):
@@ -1746,7 +1762,7 @@ def get_duck_array(self) -> np.ndarray:
     def shape(self) -> _Shape:
         return (len(self.array),)
 
-    def _convert_scalar(self, item):
+    def _convert_scalar(self, item) -> np.ndarray:
         if item is pd.NaT:
             # work around the impossibility of casting NaT with asarray
             # note: it probably would be better in general to return
@@ -1762,7 +1778,10 @@ def _convert_scalar(self, item):
             # numpy fails to convert pd.Timestamp to np.datetime64[ns]
             item = np.asarray(item.to_datetime64())
         elif self.dtype != object:
-            item = np.asarray(item, dtype=self.dtype)
+            dtype = self.dtype
+            if pd.api.types.is_extension_array_dtype(dtype):
+                dtype = get_valid_numpy_dtype(self.array)
+            item = np.asarray(item, dtype=cast(np.dtype, dtype))
 
         # as for numpy.ndarray indexing, we always want the result to be
         # a NumPy array.
@@ -1877,23 +1896,28 @@ class PandasMultiIndexingAdapter(PandasIndexingAdapter):
     __slots__ = ("_dtype", "adapter", "array", "level")
 
     array: pd.MultiIndex
-    _dtype: np.dtype
+    _dtype: np.dtype | pd.api.extensions.ExtensionDtype
     level: str | None
 
     def __init__(
         self,
         array: pd.MultiIndex,
-        dtype: DTypeLike = None,
+        dtype: DTypeLike | pd.api.extensions.ExtensionDtype | None = None,
         level: str | None = None,
     ):
         super().__init__(array, dtype)
         self.level = level
 
     def __array__(
-        self, dtype: np.typing.DTypeLike = None, /, *, copy: bool | None = None
+        self,
+        dtype: DTypeLike | pd.api.extensions.ExtensionDtype | None = None,
+        /,
+        *,
+        copy: bool | None = None,
     ) -> np.ndarray:
         if dtype is None:
             dtype = self.dtype
+        dtype = cast(np.dtype, dtype)
         if self.level is not None:
             return np.asarray(
                 self.array.get_level_values(self.level).values, dtype=dtype

xarray/core/variable.py

@@ -13,7 +13,6 @@
 import numpy as np
 import pandas as pd
 from numpy.typing import ArrayLike
-from pandas.api.types import is_extension_array_dtype
 
 import xarray as xr  # only for Dataset and DataArray
 from xarray.core import common, dtypes, duck_array_ops, indexing, nputils, ops, utils
@@ -412,6 +411,10 @@ def data(self):
         if is_duck_array(self._data):
             return self._data
         elif isinstance(self._data, indexing.ExplicitlyIndexed):
+            if pd.api.types.is_extension_array_dtype(self._data) and isinstance(
+                self._data, PandasIndexingAdapter
+            ):
+                return self._data.array
             return self._data.get_duck_array()
         else:
             return self.values
@@ -2592,11 +2595,6 @@ def chunk(  # type: ignore[override]
         dask.array.from_array
         """
 
-        if is_extension_array_dtype(self):
-            raise ValueError(
-                f"{self} was found to be a Pandas ExtensionArray.  Please convert to numpy first."
-            )
-
         if from_array_kwargs is None:
             from_array_kwargs = {}
 

xarray/namedarray/core.py

@@ -5,6 +5,7 @@
 import sys
 import warnings
 from collections.abc import Callable, Hashable, Iterable, Mapping, Sequence
+from importlib.util import find_spec
 from types import EllipsisType
 from typing import (
     TYPE_CHECKING,
@@ -261,7 +262,7 @@
         attrs: _AttrsLike = None,
     ):
         self._data = data
         self._dims = self._parse_dimensions(dims)
         self._attrs = dict(attrs) if attrs else None
 
     def __init_subclass__(cls, **kwargs: Any) -> None:
@@ -834,7 +835,18 @@
         if chunkmanager.is_chunked_array(data_old):
             data_chunked = chunkmanager.rechunk(data_old, chunks)  # type: ignore[arg-type]
         else:
-            if not isinstance(data_old, ExplicitlyIndexed):
+            if find_spec("pandas"):
+                from pandas.api.types import is_extension_array_dtype
+            else:
+
+                def is_extension_array_dtype(dtype: Any) -> Literal[False]:  # type: ignore[misc]
+                    return False
+
+            ndata: duckarray[Any, Any]
+            if is_extension_array_dtype(data_old.dtype):
+                # One of PandasExtensionArray or PandasIndexingAdapter?
+                ndata = np.asarray(data_old)
+            elif not isinstance(data_old, ExplicitlyIndexed):
                 ndata = data_old
             else:
                 # Unambiguously handle array storage backends (like NetCDF4 and h5py)

xarray/plot/dataarray_plot.py

@@ -524,7 +524,7 @@ def line(
         assert hueplt is not None
         ax.legend(handles=primitive, labels=list(hueplt.to_numpy()), title=hue_label)
 
-    if np.issubdtype(xplt.dtype, np.datetime64):
+    if isinstance(xplt.dtype, np.dtype) and np.issubdtype(xplt.dtype, np.datetime64):  # type: ignore[redundant-expr]
         _set_concise_date(ax, axis="x")
 
     _update_axes(ax, xincrease, yincrease, xscale, yscale, xticks, yticks, xlim, ylim)

xarray/tests/test_dataset.py

@@ -4317,8 +4317,13 @@ def test_setitem_pandas(self) -> None:
         ds = self.make_example_math_dataset()
         ds["x"] = np.arange(3)
         ds_copy = ds.copy()
-        ds_copy["bar"] = ds["bar"].to_pandas()
-
+        series = ds["bar"].to_pandas()
+        # to_pandas will actually give the result where the internal array of the series is a NumpyExtensionArray
+        # but ds["bar"] is a numpy array.
+        # TODO: should assert_equal be updated to handle?
+        assert (ds["bar"] == series).all()
+        del ds["bar"]
+        del ds_copy["bar"]
         assert_equal(ds, ds_copy)
 
     def test_setitem_auto_align(self) -> None:
@@ -4909,6 +4914,16 @@ def test_to_and_from_dataframe(self) -> None:
         expected = pd.DataFrame([[]], index=idx)
         assert expected.equals(actual), (expected, actual)
 
+    def test_from_dataframe_categorical_dtype_index(self) -> None:
+        cat = pd.CategoricalIndex(list("abcd"))
+        df = pd.DataFrame({"f": [0, 1, 2, 3]}, index=cat)
+        ds = df.to_xarray()
+        restored = ds.to_dataframe()
+        df.index.name = (
+            "index"  # restored gets the name because it has the coord with the name
+        )
+        pd.testing.assert_frame_equal(df, restored)
+
     def test_from_dataframe_categorical_index(self) -> None:
         cat = pd.CategoricalDtype(
             categories=["foo", "bar", "baz", "qux", "quux", "corge"]
@@ -4933,7 +4948,7 @@ def test_from_dataframe_categorical_index_string_categories(self) -> None:
         )
         ser = pd.Series(1, index=cat)
         ds = ser.to_xarray()
-        assert ds.coords.dtypes["index"] == np.dtype("O")
+        assert ds.coords.dtypes["index"] == ser.index.dtype
 
     @requires_sparse
     def test_from_dataframe_sparse(self) -> None:

xarray/tests/test_groupby.py

@@ -1118,7 +1118,8 @@ def test_groupby_math_nD_group() -> None:
     expected = da.isel(x=slice(30)) - expanded_mean
     expected["labels"] = expected.labels.broadcast_like(expected.labels2d)
     expected["num"] = expected.num.broadcast_like(expected.num2d)
-    expected["num2d_bins"] = (("x", "y"), mean.num2d_bins.data[idxr])
+    # mean.num2d_bins.data is a pandas IntervalArray so needs to be put in `numpy` to allow indexing
+    expected["num2d_bins"] = (("x", "y"), mean.num2d_bins.data.to_numpy()[idxr])
     actual = g - mean
     assert_identical(expected, actual)
 

xarray/tests/test_variable.py

@@ -656,7 +656,7 @@ def test_pandas_categorical_dtype(self):
         data = pd.Categorical(np.arange(10, dtype="int64"))
         v = self.cls("x", data)
         print(v)  # should not error
-        assert v.dtype == "int64"
+        assert v.dtype == data.dtype
 
     def test_pandas_datetime64_with_tz(self):
         data = pd.date_range(
@@ -667,9 +667,12 @@ def test_pandas_datetime64_with_tz(self):
         )
         v = self.cls("x", data)
         print(v)  # should not error
-        if "America/New_York" in str(data.dtype):
-            # pandas is new enough that it has datetime64 with timezone dtype
-            assert v.dtype == "object"
+        if v.dtype == np.dtype("O"):
+            import dask.array as da
+
+            assert isinstance(v.data, da.Array)
+        else:
+            assert v.dtype == data.dtype
 
     def test_multiindex(self):
         idx = pd.MultiIndex.from_product([list("abc"), [0, 1]])
@@ -1592,14 +1595,6 @@ def test_pandas_categorical_dtype(self):
         print(v)  # should not error
         assert pd.api.types.is_extension_array_dtype(v.dtype)
 
-    def test_pandas_categorical_no_chunk(self):
-        data = pd.Categorical(np.arange(10, dtype="int64"))
-        v = self.cls("x", data)
-        with pytest.raises(
-            ValueError, match=r".*was found to be a Pandas ExtensionArray.*"
-        ):
-            v.chunk((5,))
-
     def test_squeeze(self):
         v = Variable(["x", "y"], [[1]])
         assert_identical(Variable([], 1), v.squeeze())
@@ -2414,8 +2409,8 @@ def test_pad(self, mode, xr_arg, np_arg):
 
     def test_pandas_categorical_dtype(self):
         data = pd.Categorical(np.arange(10, dtype="int64"))
-        with pytest.raises(ValueError, match="was found to be a Pandas ExtensionArray"):
-            self.cls("x", data)
+        v = self.cls("x", data)
+        assert (v.data.compute() == data.to_numpy()).all()
 
 
 @requires_sparse
@@ -3019,7 +3014,7 @@ def test_datetime_conversion(values, unit) -> None:
     # todo: check for redundancy (suggested per review)
     dims = ["time"] if isinstance(values, np.ndarray | pd.Index | pd.Series) else []
     var = Variable(dims, values)
-    if var.dtype.kind == "M":
+    if var.dtype.kind == "M" and isinstance(var.dtype, np.dtype):
         assert var.dtype == np.dtype(f"datetime64[{unit}]")
     else:
         # The only case where a non-datetime64 dtype can occur currently is in
@@ -3061,8 +3056,12 @@ def test_pandas_two_only_datetime_conversion_warnings(
     # todo: check for redundancy (suggested per review)
     var = Variable(["time"], data.astype(dtype))  # type: ignore[arg-type]
 
-    if var.dtype.kind == "M":
+    # we internally convert series to numpy representations to avoid too much nastiness with extension arrays
+    # when calling data.array e.g., with NumpyExtensionArrays
+    if isinstance(data, pd.Series):
         assert var.dtype == np.dtype("datetime64[s]")
+    elif var.dtype.kind == "M":
+        assert var.dtype == dtype
     else:
         # The only case where a non-datetime64 dtype can occur currently is in
         # the case that the variable is backed by a timezone-aware