BUG: when attrs lost on original dataframe, copy loses the attrs as well

[snowman2]

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

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

• (optional) I have confirmed this bug exists on the master branch of pandas.

---

Possibly related to:

• Various methods don't call call __finalize__ #28283
• BUG: attrs lost for Series in DataFrame #35425

Code Sample, a copy-pastable example

df = pandas.DataFrame({"a": [1]})
df.a.attrs = {"test": "test"}
df2 = df.copy()  # same behavior for  df.reset_index()

df2.a.attrs

{}

df.a.attrs

{}

Problem description

Ideally, when making a copy, the attributes will be preserved on both dataframes.

Expected Output

df2.a.attrs

 {"test": "test"}

df.a.attrs

 {"test": "test"}

Output of pd.show_versions()

INSTALLED VERSIONS

commit : 1963b81
python : 3.7.9.final.0
python-bits : 64
OS : Linux
OS-release : 5.4.0-73-generic
Version : #82-Ubuntu SMP Wed Apr 14 17:39:42 UTC 2021
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.3.0.dev0+1660.g1963b810b3
numpy : 1.20.1
pytz : 2020.1
dateutil : 2.8.1
pip : 21.0.1
setuptools : 49.1.0
Cython : 0.29.23
pytest : 6.2.2
hypothesis : 6.13.0
sphinx : 3.5.4
blosc : 1.10.2
feather : None
xlsxwriter : 1.4.3
lxml.etree : 4.6.2
html5lib : 1.1
pymysql : None
psycopg2 : 2.8.6 (dt dec pq3 ext lo64)
jinja2 : 2.11.3
IPython : 7.20.0
pandas_datareader: None
bs4 : 4.9.3
bottleneck : 1.3.2
fsspec : 2021.05.0
fastparquet : 0.6.3
gcsfs : 2021.05.0
matplotlib : 3.3.4
numexpr : 2.7.3
odfpy : None
openpyxl : 3.0.7
pandas_gbq : None
pyarrow : 4.0.0
pyxlsb : None
s3fs : 2021.05.0
scipy : 1.6.0
sqlalchemy : 1.3.23
tables : 3.6.1
tabulate : 0.8.7
xarray : 0.17.1.dev149+g49aa235f.d20210518
xlrd : 2.0.1
xlwt : 1.3.0
numba : 0.53.1

​

[louvervecken]

I had the same issue and just opened a stackoverflow question about it.
The DataFrame attrs (empty in your example) actually seems to overwrite the Series attrs.

This seems like a serious bug as not only the result is not correct but also the instance where is copied from gets mutated. Is there any work being planned or done on this?