fix(realtime): remove only the given channel from the client

packages/realtime_client/lib/src/realtime_client.dart

@@ -459,9 +459,13 @@ class RealtimeClient {
   bool get isConnected => connectionState == SocketState.open;
 
   /// Removes a subscription from the socket.
+  ///
+  /// Matches on identity rather than on [RealtimeChannel.joinRef], which is
+  /// the empty string until a channel is subscribed and is therefore shared
+  /// by every channel that has not joined yet.
   @internal
   void remove(RealtimeChannel channel) {
-    channels = channels.where((c) => c.joinRef != channel.joinRef).toList();
+    channels = channels.where((c) => !identical(c, channel)).toList();
     if (channels.isEmpty) {
       log('transport', 'no channels remaining, scheduling disconnect');
       _schedulePendingDisconnect();

packages/realtime_client/test/socket_test.dart

@@ -613,6 +613,32 @@ void main() {
       final foundChannel = mockedSocket.channels[0];
       expect(foundChannel, channel2);
     });
+
+    test('keeps the other channels when none of them have joined', () {
+      // Channels that have never subscribed all share the empty join ref, so
+      // matching on it removed every one of them at once.
+      final socket = RealtimeClient(socketEndpoint);
+      final channel1 = socket.channel('topic-1');
+      socket.channel('topic-2');
+      socket.channel('topic-3');
+
+      socket.remove(channel1);
+
+      expect(
+        socket.channels.map((channel) => channel.topic),
+        ['realtime:topic-2', 'realtime:topic-3'],
+      );
+    });
+
+    test('removes only the given channel when topics are duplicated', () {
+      final socket = RealtimeClient(socketEndpoint);
+      final channel1 = socket.channel('topic');
+      final channel2 = socket.channel('topic');
+
+      socket.remove(channel1);
+
+      expect(socket.channels, [channel2]);
+    });
   });
 
   group('deferred disconnect', () {