fix: keep client default client read limit when realtime doesn't specify

ably/ably_test.go

@@ -492,6 +492,10 @@ type interceptConn struct {
 	active *activeIntercept
 }
 
+func (c interceptConn) Unwrap() ably.Conn {
+	return c.Conn
+}
+
 func (c interceptConn) Receive(deadline time.Time) (*ably.ProtocolMessage, error) {
 	msg, err := c.Conn.Receive(deadline)
 	if err != nil {

ably/realtime_channel_integration_test.go

@@ -294,6 +294,31 @@ func TestRealtimeChannel_ShouldSetProvidedReadLimit(t *testing.T) {
 	assert.Equal(t, int64(2048), client.Connection.ReadLimit())
 }
 
+func TestRealtimeChannel_SetDefaultReadLimitIfServerHasNoLimit(t *testing.T) {
+
+	dial := func(proto string, url *url.URL, timeout time.Duration) (ably.Conn, error) {
+		return ably.DialWebsocket(proto, url, timeout)
+	}
+	wrappedDialWebsocket, interceptMsg := DialIntercept(dial)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	msgCh := interceptMsg(ctx, ably.ActionConnected)
+
+	app, client := ablytest.NewRealtime(ably.WithDial(wrappedDialWebsocket))
+	defer safeclose(t, ablytest.FullRealtimeCloser(client), app)
+	connectedWaiter := ablytest.ConnWaiter(client, nil, ably.ConnectionEventConnected)
+
+	connectedMsg := <-msgCh
+	connectedMsg.ConnectionDetails.MaxMessageSize = 0 // 0 represents limitless message size
+	cancel()                                          // unblocks updated message to be processed
+
+	err := ablytest.Wait(connectedWaiter, nil)
+	assert.Nil(t, err)
+
+	// If server set limit is 0, value is set to default readlimit
+	assert.Equal(t, int64(65536), client.Connection.ReadLimit())
+}
+
 func TestRealtimeChannel_ShouldReturnErrorIfReadLimitExceeded(t *testing.T) {
 	app, client1 := ablytest.NewRealtime(ably.WithEchoMessages(false))
 	defer safeclose(t, ablytest.FullRealtimeCloser(client1), app)

ably/realtime_conn.go

@@ -826,7 +826,7 @@ func (c *Connection) eventloop() {
 				c.connStateTTL = connDetails.ConnectionStateTTL
 				// Spec RSA7b3, RSA7b4, RSA12a
 				c.auth.updateClientID(connDetails.ClientID)
-				if !c.isReadLimitSetExternally {
+				if !c.isReadLimitSetExternally && connDetails.MaxMessageSize > 0 {
 					c.readLimit = connDetails.MaxMessageSize // set MaxMessageSize limit as per TO3l8
 				}
 			}
@@ -988,6 +988,10 @@ func (vc verboseConn) Close() error {
 	return vc.conn.Close()
 }
 
+func (vc verboseConn) Unwrap() conn {
+	return vc.conn
+}
+
 func (c *Connection) setState(state ConnectionState, err error, retryIn time.Duration) error {
 	c.mtx.Lock()
 	defer c.mtx.Unlock()

ably/websocket.go

@@ -114,12 +114,19 @@ func dialWebsocketTimeout(uri, origin string, timeout time.Duration, agents map[
 	return c, nil
 }
 
-func setConnectionReadLimit(c conn, readLimit int64) error {
-	verboseConn, ok := c.(verboseConn)
+func unwrapConn(c conn) conn {
+	u, ok := c.(interface {
+		Unwrap() conn
+	})
 	if !ok {
-		return errors.New("cannot set readlimit for connection, connection does not use verboseConn")
+		return c
 	}
-	websocketConn, ok := verboseConn.conn.(*websocketConn)
+	return unwrapConn(u.Unwrap())
+}
+
+func setConnectionReadLimit(c conn, readLimit int64) error {
+	unwrappedConn := unwrapConn(c)
+	websocketConn, ok := unwrappedConn.(*websocketConn)
 	if !ok {
 		return errors.New("cannot set readlimit for connection, connection does not use nhooyr.io/websocket")
 	}