Broken compatibility with Python 3.8, since 2.30.0 release

[kdluzews]

Describe the bug
Since 2.30.0 release fakeredis stopped working with python 3.8. Based on my investigation the breaking changes have been introduced #388.

Given that python 3.8 is already EOL, I don't think that losing this compatibility is a problem by itself. Yet I think it should be reflected in metadata where currently required version is set to >= 3.7 to prevent installation of latest version on systems still using python 3.8 or older.

I can provide a PR if needed.

To Reproduce

(venv) ➜  /tmp/fakeredis_report_sample uv run --python 3.8 --with fakeredis==2.30.1 --with redis python
Installed 5 packages in 7ms
Python 3.8.20 (default, Sep  7 2024, 18:35:07)
[GCC 13.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import fakeredis
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/JMGy-t0wLnTZY2K0UrNGm/lib/python3.8/site-packages/fakeredis/__init__.py", line 3, in <module>
    from ._connection import (
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/JMGy-t0wLnTZY2K0UrNGm/lib/python3.8/site-packages/fakeredis/_connection.py", line 8, in <module>
    from fakeredis._fakesocket import FakeSocket
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/JMGy-t0wLnTZY2K0UrNGm/lib/python3.8/site-packages/fakeredis/_fakesocket.py", line 3, in <module>
    from fakeredis.commands_mixins import (
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/JMGy-t0wLnTZY2K0UrNGm/lib/python3.8/site-packages/fakeredis/commands_mixins/__init__.py", line 3, in <module>
    from .acl_mixin import AclCommandsMixin
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/JMGy-t0wLnTZY2K0UrNGm/lib/python3.8/site-packages/fakeredis/commands_mixins/acl_mixin.py", line 7, in <module>
    from fakeredis.model import AccessControlList
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/JMGy-t0wLnTZY2K0UrNGm/lib/python3.8/site-packages/fakeredis/model/__init__.py", line 4, in <module>
    from ._timeseries_model import TimeSeries, TimeSeriesRule, AGGREGATORS
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/JMGy-t0wLnTZY2K0UrNGm/lib/python3.8/site-packages/fakeredis/model/_timeseries_model.py", line 191, in <module>
    AGGREGATORS: Dict[bytes, Callable[[List[float]], float]] = {
TypeError: 'ABCMeta' object is not subscriptable
>>>

Expected behavior
I would expect similar behavior when trying to install latest redis-py with python 3.8, which officially dropped support for python 3.8 already:

(venv) ➜  /tmp/fakeredis_report_sample uv run --python 3.8 --with redis==6.2.0 python
  × No solution found when resolving `--with` dependencies:
  ╰─▶ Because the current Python version (3.8.20) does not satisfy Python>=3.9 and redis==6.2.0 depends on Python>=3.9, we can conclude that redis==6.2.0 cannot be used.
      And because you require redis==6.2.0, we can conclude that your requirements are unsatisfiable.

Desktop (please complete the following information):

• OS: Ubuntu 24.04
• python version: 3.8.20
• redis-py version: 6.1.1

[cunla]

python 3.8 is in EOL
I don't really see a reason to have a different error message for this, since then we would need to support poetry/uv/pip/...

[kdluzews]

Even though the 3.8 is EOL, there will be still some people using it for a while. So it is a best practice to bump the Requires-Python field in metadata, when dropping the support. Please check out official guidance how to deal outdated python versions for reference.

The Requires-Python field is part of core metadata, so we don't need to worry about the tools support.

[cunla]

python 3.8 is supported. the issue comes from redis-py

[kdluzews]

Why do you think redis-py is the problem? On the stacktrace provided you can only see fakeredis involved.

If Python 3.8 is meant to be supported, I guess there is a minor problem related to type annotations added in #388.
In _timeseries_model.py collections.abc.Callable is used for AGGREGATORS annotation, but collections.abc.Callable didn't support subscripting until Python 3.9 (PEP585 introduced it).
I would suggest switching from collections.abc.Callable to typing.Callable, which would work for all python versions. I can prepare PR with such change if you find it acceptable as a solution.

[cunla]

You are right. I fixed it in this commit

[kdluzews]

I'm afraid it not yet fixed unfortunately. Now it fails on line 24 on GenericCommandsMixin:

➜  /tmp uv run --python 3.8 --with fakeredis==2.30.2 --with redis python
Installed 5 packages in 8ms
Python 3.8.20 (default, Sep  7 2024, 18:35:07)
[GCC 13.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import fakeredis
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/Fgj81HYD0S68x2e5VesqP/lib/python3.8/site-packages/fakeredis/__init__.py", line 3, in <module>
    from ._connection import (
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/Fgj81HYD0S68x2e5VesqP/lib/python3.8/site-packages/fakeredis/_connection.py", line 8, in <module>
    from fakeredis._fakesocket import FakeSocket
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/Fgj81HYD0S68x2e5VesqP/lib/python3.8/site-packages/fakeredis/_fakesocket.py", line 3, in <module>
    from fakeredis.commands_mixins import (
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/Fgj81HYD0S68x2e5VesqP/lib/python3.8/site-packages/fakeredis/commands_mixins/__init__.py", line 6, in <module>
    from .generic_mixin import GenericCommandsMixin
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/Fgj81HYD0S68x2e5VesqP/lib/python3.8/site-packages/fakeredis/commands_mixins/generic_mixin.py", line 22, in <module>
    class GenericCommandsMixin:
  File "/home/karol.dluzewski@dynatrace.com/.cache/uv/archive-v0/Fgj81HYD0S68x2e5VesqP/lib/python3.8/site-packages/fakeredis/commands_mixins/generic_mixin.py", line 24, in GenericCommandsMixin
    _scan: Callable[[Sequence[bytes], int, bytes, ...], List[Union[bytes, List[bytes]]]]
  File "/usr/lib/python3.8/typing.py", line 816, in __getitem__
    return self.__getitem_inner__(params)
  File "/usr/lib/python3.8/typing.py", line 261, in inner
    return func(*args, **kwds)
  File "/usr/lib/python3.8/typing.py", line 839, in __getitem_inner__
    args = tuple(_type_check(arg, msg) for arg in args)
  File "/usr/lib/python3.8/typing.py", line 839, in <genexpr>
    args = tuple(_type_check(arg, msg) for arg in args)
  File "/usr/lib/python3.8/typing.py", line 149, in _type_check
    raise TypeError(f"{msg} Got {arg!r:.100}.")
TypeError: Callable[[arg, ...], result]: each arg must be a type. Got Ellipsis.
>>>

[kdluzews]

After fixing it locally, I found that there are also problems in hash_mixin.py and set_mixin.py.
Yet I see you already have found it and fixed in db2ac39. With this commit I'm able to import fakeredis with Python 3.8 without any issues.
Sorry for not verifying your changes locally, before 2.30.2 release.