reset the __eq__ and __hash__ of HTTPConnection to allow WebSockets to be added to …

[graingert]

…sets

https://github.com/tiangolo/fastapi/pull/1991/files#diff-a3e1b3437a67897cf7539e9ec348c9d8R50

[graingert]

@JayH5 is this a good change?

[tomchristie]

Could you explain the motivation a bit more clearly here?

[graingert]

@tomchristie for a number of reasons it's really useful to be able to put connections in a set. Especially websocket pubsub, see fastapi/fastapi#1991

I can see no use for comparing non-identical connections for equality

[tomchristie]

Doesn't the hash method on here already inherit object.__hash__? What am I missing?

[graingert]

Mapping overrides __eq__ which disables the default __hash__

[tomchristie]

Mapping overrides eq

Ah gotcha, thanks.
Does that mean we actually only need to override __eq__ then?

What do we think to something like the following?...

    # Don't use the `abc.Mapping.__eq__` implementation.
    # Connection instances should never be considered equal
    # unless `self is other`.
    __eq__ = object.__eq__

[graingert]

I think you need to re-enable __hash__ but I'll double check

[graingert]

@tomchristie yep you need both:

from __future__ import annotations

import collections.abc
import pytest

def test_default():
    class HTTPConnection(collections.abc.Mapping):
        def __getitem__(self, *args, **kwargs):
            return None

        def __iter__(self, *args, **kwargs):
            return self

        def __next__(self, *args, **kwargs):
            raise StopIteration

        def __len__(self, *args, **kwargs):
            return 0


    assert HTTPConnection() == HTTPConnection()
    with pytest.raises(TypeError, match=r"unhashable type: 'HTTPConnection'"):
        connections = {HTTPConnection()}


def test_eq():
    class HTTPConnection(collections.abc.Mapping):

        __eq__ = object.__eq__

        def __getitem__(self, *args, **kwargs):
            return None

        def __iter__(self, *args, **kwargs):
            return self

        def __next__(self, *args, **kwargs):
            raise StopIteration

        def __len__(self, *args, **kwargs):
            return 0


    assert HTTPConnection() != HTTPConnection()
    h = HTTPConnection()
    assert h == h

    with pytest.raises(TypeError, match=r"unhashable type: 'HTTPConnection'"):
        connections = {HTTPConnection()}



def test_eq_and_hash():
    class HTTPConnection(collections.abc.Mapping):

        __eq__ = object.__eq__
        __hash__ = object.__hash__

        def __getitem__(self, *args, **kwargs):
            return None

        def __iter__(self, *args, **kwargs):
            return self

        def __next__(self, *args, **kwargs):
            raise StopIteration

        def __len__(self, *args, **kwargs):
            return 0


    assert HTTPConnection() != HTTPConnection()
    h = HTTPConnection()
    assert h == h

    assert {HTTPConnection()} != {HTTPConnection()}
    assert h in {h}
    assert {h} == {h}

[tomchristie]

Okay, fair enough. 😄

[tomchristie]

Yup, that's all neat enough. 👍