gh-88427: Deprecate socket.SocketType

[rruuaanng]

I propose to deprecate socket.SocketType. There's no reason to publicly expose _socket.socket separately from socket.socket, the only type that moat users should care about.
SocketType isn't needed for type checking; socket.socket is itself a class and can be used in type annotations.

cc @JelleZijlstra

• Issue: SocketType documentation misleading #88427

[ZeroIntensity]

SocketType isn't deprecated right now, so we can't remove it yet.

Please update the PR to raise a DeprecationWarning when accessing a SocketType (you can do this via a PEP-562 __getattr__), and then add the documentation notes.

[rruuaanng]

Maybe we can wait for the promoter to answer. I won't open this PR before I decide whether to abandon or remove it.

[JelleZijlstra]

I looked at the code again and agree with my opinion from 2021: it should be deprecated and eventually removed.

It could be useful to do a code search (e.g., GitHub code search, Hugo's top 5k pypi packages tool) to see how the name is being used.

A possible approach to deprecation could be to remove the current line adding it to _socket, and add a module __getattr__ to both the _socket and socket modules that raises a DeprecationWarning and then returns _socket.socket.

[rruuaanng]

Okay, I'll re-revise this PR so that it throws a warning when calling this type. Call me back in this PR when we consider removing it in the future :)

[rruuaanng]

It seems that the module __getattr__ only works for attributes that do not exist, which makes it necessary to remove the export in socketmodule. But it triggers a deprecation warning. Emmm...

[picnixz]

It seems that the module getattr only works for attributes that do not exist, which makes it necessary to remove the export in socketmodule. But it triggers a deprecation warning. Emmm...

It works for any kind of attributes. Please, read PEP-562 for examples on how to use it.

[rruuaanng]

It seems that the module getattr only works for attributes that do not exist, which makes it necessary to remove the export in socketmodule. But it triggers a deprecation warning. Emmm...

It works for any kind of attributes. Please, read PEP-562 for examples on how to use it.

I read the document and modified it. But why does it trigger this

Traceback (most recent call last):
  File "D:\a\cpython\cpython\Lib\test\pythoninfo.py", line 1062, in collect_info
    collect_func(info_add)
    ~~~~~~~~~~~~^^^^^^^^^^
  File "D:\a\cpython\cpython\Lib\test\pythoninfo.py", line 727, in collect_test_socket
    from test import test_socket
  File "D:\a\cpython\cpython\Lib\test\test_socket.py", line 201, in <module>
    HAVE_SOCKET_CAN = _have_socket_can()
  File "D:\a\cpython\cpython\Lib\test\test_socket.py", line 104, in _have_socket_can
    s = socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
  File "D:\a\cpython\cpython\Lib\socket.py", line 242, in __init__
    _socket.socket.__init__(self, family, type, proto, fileno)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'NoneType' object cannot be interpreted as an integer

Edit
It seems to be a consistent bug since I opened the PR.

[ZeroIntensity]

I think you need to raise an AttributeError from the __getattr__ if it isn't SocketType.

[vstinner]

@rruuaanng: Did you try your change before updating the PR? It doesn't work, no warning is emitted:

$ ./python
>>> import _socket
>>> _socket.SocketType
<class '_socket.socket'>

I suggest to mark the PR as a draft since it changes many times in a short time.

[rruuaanng]

@vstinner
I forgot the most important step, removing its definition, and now it can successfully trigger deprecation ;-)

>>> import _socket
>>> _socket.SocketType
<python-input-1>:1: DeprecationWarning: It will be removed in 3.16. Use socket.socket type instead
  _socket.SocketType
<class '_socket.socket'>

[vstinner]

I forgot the most important step

Right. Please test your change before publishing it.

[rruuaanng]

Please allow me to check again to see if there are any unresolved comments to decide whether we should remove the DO_NOT_MERGE tag.

[vstinner]

test_socket and test_pickle are failing on the CI Ubuntu.

[rruuaanng]

Oh.... I don't understand, I was looking for what was throwing the error so I ran the failing tests locally and it seemed like they all worked fine on my computer.

test_socket.py

PS E:\code\github\cpython\alpha\cpython-main> ./python -m unittest Lib\test\test_socket.py
Running Release|x64 interpreter...
.ss.sssssssss.......sssssssss.......................sss...ssss........ssssss.....................s...........................E:\code\github\cpython\alpha\cpython-main\Lib\socket.py:74: DeprecationWarning: _socket.SocketType is deprecated and will be removed in Python 3.16. Use socket.socket instead
  return _socket.SocketType
.s........s...s............sss.......s..........ssssss..s.s.ssssssssssss..........sssssss...............s..ss.....sssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss...........ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss...........s..ss..ssssss.s.....sssssssss...............................................
----------------------------------------------------------------------
Ran 732 tests in 69.918s

OK (skipped=485)

test_pickle.py

PS E:\code\github\cpython\alpha\cpython-main> ./python -m unittest Lib\test\test_pickle.py
Running Release|x64 interpreter...
...........s.................................................................................................................................s...........................................................................................................................................................s........................sss..............sss.......Can't import module 'multiprocessing.popen_fork': module 'os' has no attribute 'WNOHANG'
No module named '_gdbm'
No module named '_gdbm'
No module named 'dbm.bsd'
No module named '_dummy_thread'
No module named '_dbm'
No module named '_dbm'
.No module named '_dummy_thread'
No module named 'dbm.bsd'
No module named '_dbm'
No module named '_gdbm'
No module named '_dbm'
No module named '_gdbm'
..Can't import module 'multiprocessing.popen_fork': module 'os' has no attribute 'WNOHANG'
E:\code\github\cpython\alpha\cpython-main\Lib\socket.py:74: DeprecationWarning: _socket.SocketType is deprecated and will be removed in Python 3.16. Use socket.socket instead
  return _socket.SocketType
.No module named '_dummy_thread'
No module named '_dummy_thread'
No module named 'dbm.bsd'
No module named 'dbm.bsd'
No module named '_dbm'
No module named '_dbm'
No module named '_gdbm'
No module named '_gdbm'
.Can't import module 'multiprocessing.popen_fork': module 'os' has no attribute 'WNOHANG'
E:\code\github\cpython\alpha\cpython-main\Lib\socket.py:74: DeprecationWarning: _socket.SocketType is deprecated and will be removed in Python 3.16. Use socket.socket instead
  return _socket.SocketType
....s..........................................................................................................................s...............................sssss....sss......................sss...........................................................................................................s............................................................................................................................s......................................................sss..............sss........
----------------------------------------------------------------------
Ran 865 tests in 13.836s

OK (skipped=30)

I tried removing my changes and ran test_pickle.py again, but the only difference was that the deprecation was gone.

PS E:\code\github\cpython\alpha\cpython-main> ./python -m unittest Lib\test\test_pickle.py
Running Release|x64 interpreter...
...........s.................................................................................................................................s...........................................................................................................................................................s........................sss..............sss.......No module named '_gdbm'
Can't import module 'multiprocessing.popen_fork': module 'os' has no attribute 'WNOHANG'
No module named '_dbm'
No module named 'dbm.bsd'
No module named '_dummy_thread'
No module named '_gdbm'
No module named '_dbm'
.No module named '_dummy_thread'
No module named 'dbm.bsd'
No module named '_dbm'
No module named '_gdbm'
No module named '_dbm'
No module named '_gdbm'
..Can't import module 'multiprocessing.popen_fork': module 'os' has no attribute 'WNOHANG'
.No module named '_dummy_thread'
No module named '_dummy_thread'
No module named 'dbm.bsd'
No module named 'dbm.bsd'
No module named '_dbm'
No module named '_dbm'
No module named '_gdbm'
No module named '_gdbm'
.Can't import module 'multiprocessing.popen_fork': module 'os' has no attribute 'WNOHANG'
....s..........................................................................................................................s...............................sssss....sss......................sss...........................................................................................................s............................................................................................................................s......................................................sss..............sss........
----------------------------------------------------------------------
Ran 865 tests in 15.947s

OK (skipped=30)

test_socket.py passes the test perfectly fine and throws the deprecation, but test_pickle.py seems to throw an error that seems unrelated to the PR. But it is undeniable that my CI did not pass :(

Edit

test_pickle.py threw the same exception as my local test results on all three platforms.

[ZeroIntensity]

Should sock_type get INCREF'd? I'm assuming its a static type and therefore immortal, but we should add a comment clarifying that.

[rruuaanng]

I tried to search for situations where sock_type is used in socketmodule.c. In the scenario where Py_DECREF is used, only socket_clear uses Py_DECREF. And sock_type does not use Py_INCREF. And in other parts, it seems that there is no special comment.