`BytesMessage.data` is a `bytearray` but type-hinted as `bytes`

[frankie567]

I'm using wsproto in my library httpx-ws. One contributor reported in frankie567/httpx-ws#38, that the data property of BytesMessage is actually a bytearray at runtime, but it's typed as bytes.

Reproducible example

from wsproto import WSConnection, ConnectionType
from wsproto.events import Request, BytesMessage, AcceptConnection

client = WSConnection(ConnectionType.CLIENT)
server = WSConnection(ConnectionType.SERVER)

msg = client.send(Request(host='echo.websocket.org', target='/'))
server.receive_data(msg)

msg = server.send(AcceptConnection())
client.receive_data(msg)

msg = server.send(BytesMessage(b"Hello"))
client.receive_data(msg)

for event in client.events():
    if isinstance(event, BytesMessage):
        print(type(event.data))  # bytearray

Additional comment

It's not really a problem since bytes and bytearray are nearly the same, but from type-hints point-of-view, maybe BytesMessage.data should be typed as bytearray.

[njsmith]

Oh interesting. The type should probably be "bytes | bytearray", ie you should assume it's something that quacks like a bytes but maybe not that exactly. And it looks like this is actually what the type already is, of you're using mypy: python/typing#552 But apparently mypy didn't get around to pushing this upstream to the standards – so I'm guessing that pyright doesn't implement this little hack, and these days it's popular enough that this matters? (I guess we should confirm that. If pyright also has this hack then we might not want to bother fixing it.)

…

On Wed, Jul 12, 2023, 04:57 François Voron ***@***.***> wrote: I'm using wsproto in my library httpx-ws. One contributor reported in frankie567/httpx-ws#38 <frankie567/httpx-ws#38>, that the data property of BytesMessage is actually a bytearray at runtime, but it's typed as bytes. Reproducible example from wsproto import WSConnection, ConnectionTypefrom wsproto.events import Request, BytesMessage, AcceptConnection client = WSConnection(ConnectionType.CLIENT)server = WSConnection(ConnectionType.SERVER) msg = client.send(Request(host='echo.websocket.org', target='/'))server.receive_data(msg) msg = server.send(AcceptConnection())client.receive_data(msg) msg = server.send(BytesMessage(b"Hello"))client.receive_data(msg) for event in client.events(): if isinstance(event, BytesMessage): print(type(event.data)) # bytearray Additional comment It's not really a problem since bytes and bytearray are nearly the same, but from type-hints point-of-view, maybe BytesMessage.data should be typed as bytearray. — Reply to this email directly, view it on GitHub <#185>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAEU42EXXHAVURZXLCWPX5LXP2GLNANCNFSM6AAAAAA2HMABXA> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Kriechi]

I'm leaning towards simply ignoring the mypy errors in this case. As mentioned in python/typing#552 (comment), bytearray can be considered bytes during type checking. Not sure why mypy complains here. The newer ty type checker is mostly happy, though I will push some smaller fixes here too.