BUG: sort_values raises error about Categorical categories must be unique when no categorical types used

[rohanjain101]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

>>> s1 = pd.Series([-0.0, 0.0], dtype="float[pyarrow]")
>>> s2 = pd.Series([False, False], dtype="bool[pyarrow]")
>>> df = pd.DataFrame({"A": s1, "B": s2})
>>> df.sort_values(list(df.columns))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\ps_311_0722\Lib\site-packages\pandas\core\frame.py", line 6751, in sort_values
    indexer = lexsort_indexer(
              ^^^^^^^^^^^^^^^^
  File "C:\ps_311_0722\Lib\site-packages\pandas\core\sorting.py", line 341, in lexsort_indexer
    cat = Categorical(k, ordered=True)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\ps_311_0722\Lib\site-packages\pandas\core\arrays\categorical.py", line 438, in __init__
    dtype = CategoricalDtype(categories, dtype.ordered)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\ps_311_0722\Lib\site-packages\pandas\core\dtypes\dtypes.py", line 187, in __init__
    self._finalize(categories, ordered, fastpath=False)
  File "C:\ps_311_0722\Lib\site-packages\pandas\core\dtypes\dtypes.py", line 344, in _finalize
    categories = self.validate_categories(categories, fastpath=fastpath)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\ps_311_0722\Lib\site-packages\pandas\core\dtypes\dtypes.py", line 540, in validate_categories
    raise ValueError("Categorical categories must be unique")
ValueError: Categorical categories must be unique
>>>

Issue Description

There's no categorical types used in the above example, so error is unexpected.

Expected Behavior

df is already sorted, so I expect it to be returned without raising an error.

Installed Versions

INSTALLED VERSIONS

commit : ba1cccd
python : 3.11.2.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.22621
machine : AMD64
processor : Intel64 Family 6 Model 85 Stepping 7, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_United States.1252

pandas : 2.1.0
numpy : 1.25.2
pytz : 2023.3
dateutil : 2.8.2
setuptools : 68.0.0
pip : 23.2.1
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader : None
bs4 : None
bottleneck : None
dataframe-api-compat: None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 13.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None

[lukemanley]

Thanks for the report. It looks like this is raising in Categorical:

import pandas as pd

ser = pd.Series([-0.0, 0.0], dtype="float[pyarrow]")
pd.Categorical(ser)

[lukemanley]

More specifically, this looks like the disconnect:

In [1]: import pandas as pd

In [2]: arr = pd.array([-0.0, 0.0], dtype="float[pyarrow]")

In [3]: pd.Series(arr).is_unique
Out[3]: True

In [4]: pd.Index(arr).is_unique
Out[4]: False

[lukemanley]

xref: apache/arrow#26214

[mroeschke]

Closing as awaiting resolution in apache/arrow#26214