feat(socketio): send close reason when emitting Event::Close

Previously, when we emitted an Event::Close, we didn't specify a
reason for why this event was emitted. When implementing the close
notification on unexpected transport closes, we started sending
'transport close' as the payload for the close event.

We now decided to do this more consistently and added a close reason
when emitting the Event::Close, so that the client better knows
why this event was emitted.

socketio/src/asynchronous/client/client.rs

@@ -19,7 +19,7 @@ use crate::{
     asynchronous::socket::Socket as InnerSocket,
     error::{Error, Result},
     packet::{Packet, PacketId},
-    Event, Payload,
+    CloseReason, Event, Payload,
 };
 
 #[derive(Default)]
@@ -168,7 +168,7 @@ impl Client {
                         // We don't need to do that in the other cases, since proper server close
                         // and manual client close are handled explicitly.
                         if let Some(err) = client_clone
-                            .callback(&Event::Close, "transport close")
+                            .callback(&Event::Close, CloseReason::TransportClose.as_str())
                             .await
                             .err()
                         {
@@ -524,7 +524,8 @@ impl Client {
                 }
                 PacketId::Disconnect => {
                     *(self.disconnect_reason.write().await) = DisconnectReason::Server;
-                    self.callback(&Event::Close, "").await?;
+                    self.callback(&Event::Close, CloseReason::IOServerDisconnect.as_str())
+                        .await?;
                 }
                 PacketId::ConnectError => {
                     self.callback(
@@ -604,8 +605,7 @@ mod test {
         },
         error::Result,
         packet::{Packet, PacketId},
-        Event,
-        Payload, TransportType,
+        CloseReason, Event, Payload, TransportType,
     };
 
     #[tokio::test]
@@ -977,7 +977,10 @@ mod test {
         let rx_timeout = timeout(Duration::from_secs(1), rx.recv()).await;
         assert!(rx_timeout.is_ok());
 
-        assert_eq!(rx_timeout.unwrap(), Some(Payload::from("transport close")));
+        assert_eq!(
+            rx_timeout.unwrap(),
+            Some(Payload::from(CloseReason::TransportClose.as_str()))
+        );
 
         Ok(())
     }

socketio/src/client/raw_client.rs

@@ -1,7 +1,7 @@
 use super::callback::Callback;
 use crate::packet::{Packet, PacketId};
 use crate::Error;
-pub(crate) use crate::{event::Event, payload::Payload};
+pub(crate) use crate::{event::CloseReason, event::Event, payload::Payload};
 use rand::{thread_rng, Rng};
 use serde_json::Value;
 
@@ -149,7 +149,7 @@ impl RawClient {
         let _ = self.socket.send(disconnect_packet);
         self.socket.disconnect()?;
 
-        let _ = self.callback(&Event::Close, ""); // trigger on_close
+        let _ = self.callback(&Event::Close, CloseReason::IOClientDisconnect.as_str()); // trigger on_close
         Ok(())
     }
 
@@ -372,7 +372,7 @@ impl RawClient {
                     self.callback(&Event::Connect, "")?;
                 }
                 PacketId::Disconnect => {
-                    self.callback(&Event::Close, "")?;
+                    self.callback(&Event::Close, CloseReason::IOServerDisconnect.as_str())?;
                 }
                 PacketId::ConnectError => {
                     self.callback(

socketio/src/event.rs

@@ -57,3 +57,38 @@ impl Display for Event {
         f.write_str(self.as_str())
     }
 }
+
+/// A `CloseReason` is the payload of the [`Event::Close`] and specifies the reason for
+/// why it was fired.
+/// These are aligned with the official Socket.IO disconnect reasons, see
+/// https://socket.io/docs/v4/client-socket-instance/#disconnect
+#[derive(Debug, PartialEq, PartialOrd, Clone, Eq, Hash)]
+pub enum CloseReason {
+    IOServerDisconnect,
+    IOClientDisconnect,
+    TransportClose,
+}
+
+impl CloseReason {
+    pub fn as_str(&self) -> &str {
+        match self {
+            // Inspired by https://github.com/socketio/socket.io/blob/d0fc72042068e7eaef448941add617f05e1ec236/packages/socket.io-client/lib/socket.ts#L865
+            CloseReason::IOServerDisconnect => "io server disconnect",
+            // Inspired by https://github.com/socketio/socket.io/blob/d0fc72042068e7eaef448941add617f05e1ec236/packages/socket.io-client/lib/socket.ts#L911
+            CloseReason::IOClientDisconnect => "io client disconnect",
+            CloseReason::TransportClose => "transport close",
+        }
+    }
+}
+
+impl From<CloseReason> for String {
+    fn from(event: CloseReason) -> Self {
+        Self::from(event.as_str())
+    }
+}
+
+impl Display for CloseReason {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        f.write_str(self.as_str())
+    }
+}

socketio/src/lib.rs

@@ -191,7 +191,7 @@ pub mod asynchronous;
 
 pub use error::Error;
 
-pub use {event::Event, payload::Payload};
+pub use {event::CloseReason, event::Event, payload::Payload};
 
 pub use client::{ClientBuilder, RawClient, TransportType};