The subclass of dict is not respected on >=2024.11.0

[emmaai]

Describe the issue:
The subclass is not respected. I noticed the issue on subclass of dict, not sure if it's more general. See below for details.

Minimal Complete Verifiable Example:

from dask.distributed import Client, as_completed

class TestDict(dict):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

    def __getattr__(self, key: str):
        """ Allow access to items as attributes. """
        v = self.get(key, self)
        if v is self:
            raise AttributeError("has no attribute '{}'".format(key))
        return v

    def __repr__(self) -> str:
        return "(TestDict{})".format(super().__repr__())


def test_subclass(test_dict):
    print(f'input type {type(test_dict)}')
    print(f'get val {test_dict.a}')
    return 0


def main():
    client = Client()
    test_dict = TestDict(a=1)
    futures = [client.submit(test_subclass, test_dict)]
    for f in as_completed(futures):
        res = f.result()
        print(f"result {res}")


if __name__ == "__main__":
    main()

Anything else we need to know?:

The test code works as expected on <2024.11.0, which outputs

input type <class '__main__.TestDict'>
get val 1
result 0

on >=2024.11.0 outputs

input type <class 'dict'>
2024-11-13 05:01:36,954 - distributed.worker - ERROR - Compute Failed
Key:       test_subclass-e8dd185fef44ec112f057d9b352f913f
State:     executing
Task:  <Task 'test_subclass-e8dd185fef44ec112f057d9b352f913f' test_subclass(...)>
Exception: 'AttributeError("\'dict\' object has no attribute \'a\'")'
Traceback: '  File "/home/ubuntu/data/home/ubuntu/test_dask.py", line 20, in test_subclass\n    print(f\'get val {test_dict.a}\')\n'

Traceback (most recent call last):
  File "/home/ubuntu/data/home/ubuntu/test_dask.py", line 34, in <module>
    main()
  File "/home/ubuntu/data/home/ubuntu/test_dask.py", line 29, in main
    res = f.result()
  File "/home/ubuntu/.local/lib/python3.10/site-packages/distributed/client.py", line 402, in result
    return self.client.sync(self._result, callback_timeout=timeout)
  File "/home/ubuntu/data/home/ubuntu/test_dask.py", line 20, in test_subclass
    print(f'get val {test_dict.a}')

Environment:

• Dask version: 2024.11.0
• Python version: 3.10
• Operating System: ubuntu 22.04
• Install method (conda, pip, source): pip

[templiert]

I am experiencing the same issue with DotMap objects, which are a dict subclass with dot-access.
It is probably covered by the good general MCVE exposed by @emmaai.
Below is a MCVE modified from @emmaai that breaks with DotMap objects.

from distributed import Client
from dotmap import DotMap


def test_subclass(test_dict):
    print(f"input type {type(test_dict)}")
    print(f"get val {test_dict.a}")
    return 0


def main():
    with Client() as client:
        print(client.submit(test_subclass, DotMap({"a": 1})).result())


if __name__ == "__main__":
    main()

input type <class 'dict'>
2024-11-18 12:33:05,966 - distributed.worker - ERROR - Compute Failed
Key:       test_subclass-fc48deb6364566a152c9e2cd5c01bf6d
State:     executing
Task:  <Task 'test_subclass-fc48deb6364566a152c9e2cd5c01bf6d' test_subclass(...)>
Exception: 'AttributeError("\'dict\' object has no attribute \'a\'")'
Traceback: '  File "C:\\software\\repos\\myapp\\tests\\dotmap_dask_202411.py", line 7, in test_subclass\n    print(f"get val {test_dict.a}")\n                     ^^^^^^^^^^^\n'

Traceback (most recent call last):
  File "C:\software\repos\myapp\tests\dotmap_dask_202411.py", line 17, in <module>
    main()
  File "C:\software\repos\myapp\tests\dotmap_dask_202411.py", line 13, in main
    print(client.submit(test_subclass, DotMap({"a": 1})).result())
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\software\miniforge\envs\ibeammsem\Lib\site-packages\distributed\client.py", line 402, in result
    return self.client.sync(self._result, callback_timeout=timeout)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\software\repos\myapp\tests\dotmap_dask_202411.py", line 7, in test_subclass
    print(f"get val {test_dict.a}")
      ^^^^^^^^^^^^^^^^^
AttributeError: 'dict' object has no attribute 'a'

INSTALLED VERSIONS
------------------
commit: None
python: 3.12.5 | packaged by conda-forge | (main, Aug  8 2024, 18:24:51) [MSC v.1940 64 bit (AMD64)]
python-bits: 64
OS: Windows
OS-release: 11
machine: AMD64
processor: Intel64 Family 6 Model 186 Stepping 2, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: ('English_United States', '1252')
libhdf5: None
libnetcdf: None

xarray: 2024.10.0
pandas: 2.2.2
numpy: 1.26.4
scipy: 1.14.0
netCDF4: None
pydap: None
h5netcdf: None
h5py: None
zarr: 2.18.3
cftime: None
nc_time_axis: None
iris: None
bottleneck: 1.4.2
dask: 2024.11.2
distributed: 2024.11.2
matplotlib: 3.9.2
cartopy: None
seaborn: None
numbagg: None
fsspec: 2024.6.1
cupy: None
pint: None
sparse: None
flox: None
numpy_groupies: None
setuptools: 72.1.0
pip: 24.2
conda: None
pytest: None
mypy: None
IPython: 8.26.0
sphinx: None

[jacobtomlinson]

Looks like this bug was introduced in #8797. cc @fjetter