fix(webtransport-websys): Allow poll_flush after poll_close

This removes a `debug_assert` from `poll_flush` because it can be valid for the user to recheck the flush state. In that case the operation should be noop.

A real life code that triggers this assertition is [this](https://github.com/libp2p/rust-asynchronous-codec/blob/c818a83906891caf8aadcae8f899727c2c8393a8/src/framed_write.rs#L263-L266).

Fixes #5618

Pull-Request: #6193.

Author: oblique

Cargo.lock

@@ -114,7 +114,7 @@ libp2p-webrtc-utils = { version = "0.4.0", path = "misc/webrtc-utils" }
 libp2p-webrtc-websys = { version = "0.4.0", path = "transports/webrtc-websys" }
 libp2p-websocket = { version = "0.45.2", path = "transports/websocket" }
 libp2p-websocket-websys = { version = "0.5.0", path = "transports/websocket-websys" }
-libp2p-webtransport-websys = { version = "0.5.1", path = "transports/webtransport-websys" }
+libp2p-webtransport-websys = { version = "0.5.2", path = "transports/webtransport-websys" }
 libp2p-yamux = { version = "0.47.0", path = "muxers/yamux" }
 
 # External dependencies

Cargo.toml

@@ -1,3 +1,8 @@
+## 0.5.2
+
+- Remove `poll_flush called after poll_close` assertion.
+  See [PR 6193](https://github.com/libp2p/rust-libp2p/pull/6193).
+
 ## 0.5.1
 
 - Remove `once_cell` dependency.

transports/webtransport-websys/CHANGELOG.md

@@ -3,7 +3,7 @@ name = "libp2p-webtransport-websys"
 edition.workspace = true
 rust-version = { workspace = true }
 description = "WebTransport for libp2p under WASM environment"
-version = "0.5.1"
+version = "0.5.2"
 authors = [
     "Yiannis Marangos <[email protected]>",
     "oblique <[email protected]>",

transports/webtransport-websys/Cargo.toml

@@ -153,10 +153,6 @@ impl StreamInner {
             // messages were flushed.
             self.poll_writer_ready(cx)
         } else {
-            debug_assert!(
-                false,
-                "libp2p_webtransport_websys::Stream: poll_flush called after poll_close"
-            );
             Poll::Ready(Ok(()))
         }
     }