Access to the underlying tungstenite WebSocketStream config

[mr-ns]

I would like to be able to configure things like the max message size when using Poem's WebSocket. This is available on the underlying tungstenite WebSocketStream that Poem wraps, but I do not see it exposed through Poem. The end result is something like the following, which seems … less than ideal:

#[handler]
pub async fn handler(ws: WebSocket) -> impl IntoResponse {
    ws.on_upgrade(|mut socket| async move {
        unsafe {
            let poem_stream: *const poem::web::websocket::WebSocketStream = &socket;
            let tung_stream = poem_stream as *const tokio_tungstenite::WebSocketStream<poem::Upgraded>;

            let config_const: *const tungstenite::protocol::WebSocketConfig = (*tung_stream).get_config();
            let config = config_const as *mut tungstenite::protocol::WebSocketConfig;

            (*config).max_message_size = Some(32 << 20);
            (*config).max_frame_size = Some(8 << 20);
        }
...

The pointers do not bother me (hey, I grew up on C), but two other things do:

1. The let tung_stream = poem_stream as ... cast assumes the tungstenite WebSocketStream is the first member in the Poem WebSocketStream; that is fragile at best.
2. Coercing mutability onto the reference returned by get_config() could have unintended side effects. After all, if the tungstenite folks wanted the stream config to be changeable they would have returned a mutable reference in the first place.

Have I overlooked some "blessed" way to configure the WebSocketStream?

[sunli829]

Added WebSocket::config method in poem v3.1.1

[mr-ns]

Cool! So we would call WebSocket::config() in the handler right before WebSocket::on_upgrade() ?

[sunli829]

yes

[mr-ns]

Sweet! Thank you!

[mr-ns]

@sunli829 — Thank you again for your quick attention to this request. Now that I am using this I have come across another desire; that is, the ability to get the current configuration. For reference, the tungstenite library has a get_config() method on both the WebSocket and WebSocketStream. Can we expose those through the Poem layer? In particular, the ability to get the config from the stream would be very nice.

Thank you!

[mr-ns]

@sunli829 — Any thoughts here? Should I open a new request for this?

[mr-ns]

@sunli829 — I implemented this for WebSocketStream and submitted PR #900. The implementation (intentionally) mirrors that of the tungstenite equivalent.