fix(webrtc-utils): read buffer only if empty message

This PR adds a return of `Poll::Ready(Ok(0))` when the `message` vector is empty or not present.

This missing return was causing the stream not to finish, then to be dropped, causing the request response protocol to fail over WebRTC.

Now that empty or non existent message vectors get returned as `Ok(0)` the stream can be read and request response works now over WebRTC.

Pull-Request: #5439.

Cargo.toml

@@ -110,7 +110,7 @@ libp2p-tls = { version = "0.4.0", path = "transports/tls" }
 libp2p-uds = { version = "0.40.0", path = "transports/uds" }
 libp2p-upnp = { version = "0.2.2", path = "protocols/upnp" }
 libp2p-webrtc = { version = "0.7.1-alpha", path = "transports/webrtc" }
-libp2p-webrtc-utils = { version = "0.2.0", path = "misc/webrtc-utils" }
+libp2p-webrtc-utils = { version = "0.2.1", path = "misc/webrtc-utils" }
 libp2p-webrtc-websys = { version = "0.3.0-alpha", path = "transports/webrtc-websys" }
 libp2p-websocket = { version = "0.43.0", path = "transports/websocket" }
 libp2p-websocket-websys = { version = "0.3.2", path = "transports/websocket-websys" }

misc/webrtc-utils/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.2.1
+
+- Fix end of stream handling when buffer is empty or not present.
+  See [PR 5439](https://github.com/libp2p/rust-libp2p/pull/5439).
+
 ## 0.2.0
 
 - Update to latest version of `libp2p-noise`.

misc/webrtc-utils/Cargo.toml

@@ -7,7 +7,7 @@ license = "MIT"
 name = "libp2p-webrtc-utils"
 repository = "https://github.com/libp2p/rust-libp2p"
 rust-version = { workspace = true }
-version = "0.2.0"
+version = "0.2.1"
 publish = true
 
 [dependencies]

misc/webrtc-utils/src/stream.rs

@@ -146,8 +146,14 @@ where
                     }
 
                     debug_assert!(read_buffer.is_empty());
-                    if let Some(message) = message {
-                        *read_buffer = message.into();
+                    match message {
+                        Some(msg) if !msg.is_empty() => {
+                            *read_buffer = msg.into();
+                        }
+                        _ => {
+                            tracing::debug!("poll_read buffer is empty, received None");
+                            return Poll::Ready(Ok(0));
+                        }
                     }
                 }
                 None => {