BUG: `isna` on pyarrow backed Series is returning Series with `bool` dtype instead of `bool[pyarrow]`

[thesword53]

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

>>> s = pd.Series([0, None, 4, 5], dtype="u1[pyarrow]")
>>> s
0       0
1    <NA>
2       4
3       5
dtype: uint8[pyarrow]

>>> s.isna()
0    False
1     True
2    False
3    False
dtype: bool

Issue Description

s.isna().dtype is BoolDType (bool) instead of ArrowDtype(pa.bool_()) (bool[pyarrow])

Expected Behavior

>>> s.isna()
0    False
1     True
2    False
3    False
dtype: bool[pyarrow]

Installed Versions

INSTALLED VERSIONS

commit : d9cdd2e
python : 3.11.9.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19045
machine : AMD64
processor : AMD64 Family 23 Model 113 Stepping 0, AuthenticAMD
byteorder : little
LC_ALL : None
LANG : fr_FR.UTF-8
LOCALE : fr_FR.cp1252

pandas : 2.2.2
numpy : 2.0.1
pytz : 2024.1
dateutil : 2.9.0
setuptools : 70.2.0
pip : None
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 5.2.2
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 3.1.4
IPython : 8.22.2
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.9.0
numba : None
numexpr : 2.10.1
odfpy : None
openpyxl : 3.1.5
pandas_gbq : None
pyarrow : 17.0.0
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.14.0
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2024.1
qtpy : None
pyqt5 : None

[loicdiridollou]

Hey @thesword53,
I realized that issue also affected something I am working on so I went down the rabbit hole and it seems like what is happening is that the Series gets cast to a np.ndarray then the is isna operation gets applied and when they rebuild the Series object, we lose the original type (pyarrow) and it seems like it just rebuilds without any assumption of type (as we pass an np.ndarray of bool it just set the type of the Series to bool and not bool[pyarrow]).

pandas/pandas/core/dtypes/missing.py

Lines 208 to 210 in aa134bb

	# box
	result = obj._constructor(result, index=obj.index, name=obj.name, copy=False)
	return result

This also affects if you create a Dataframe where the type of the column was originally uint8[pyarrow] and it gets cast into bool and not bool[pyarrow].

[KevsterAmp]

I'd like to work on this

[KevsterAmp]

take

[KevsterAmp]

take

[KevsterAmp]

take

[KevsterAmp]

Can't seem to assign the issue to myself, but I'll be opening a PR for this in a bit. Thanks @loicdiridollou for further investigating

[KevsterAmp]

Take