[ECO-5163] fix: duplicated messages because of duplicated attach message

lib/src/main/java/io/ably/lib/realtime/ChannelBase.java

@@ -243,6 +243,13 @@ private void attachImpl(final boolean forceReattach, final CompletionListener li
             throw AblyException.fromErrorInfo(connectionManager.getStateErrorInfo());
         }
 
+        // (RTL4i)
+        if (connectionManager.getConnectionState().state == ConnectionState.connecting
+            || connectionManager.getConnectionState().state == ConnectionState.disconnected) {
+            setState(ChannelState.attaching, null);
+            return;
+        }
+
         /* send attach request and pending state */
         Log.v(TAG, "attach(); channel = " + name + "; sending ATTACH request");
         ProtocolMessage attachMessage = new ProtocolMessage(Action.attach, this.name);

lib/src/test/java/io/ably/lib/test/realtime/RealtimeMessageTest.java

@@ -13,12 +13,16 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
 
 import com.google.gson.Gson;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonPrimitive;
+import io.ably.lib.types.ChannelOptions;
 import io.ably.lib.types.MessageAction;
 import io.ably.lib.types.MessageExtras;
 import io.ably.lib.types.Param;
@@ -1010,4 +1014,42 @@ public void should_have_serial_action_createdAt() throws AblyException {
             assertNull(msgComplete.waitFor(1, 10_000));
         }
     }
+
+    @Test
+    public void should_not_duplicate_messages() throws Exception {
+        ClientOptions opts = createOptions(testVars.keys[0].keyStr);
+        opts.logLevel = 2;
+        String testChannelName = "my-channel" + System.currentTimeMillis();
+        try (AblyRest rest = new AblyRest(opts)) {
+            final io.ably.lib.rest.Channel channel = rest.channels.get(testChannelName);
+            List<String> testMessagesData = List.of("message 1", "message 2", "message 3");
+            List<Message> messages = testMessagesData
+                .stream()
+                .map(data -> new Message("name", data))
+                .collect(Collectors.toList());
+            channel.publish(messages.toArray(Message[]::new));
+        }
+
+        try (AblyRealtime realtime = new AblyRealtime(opts)) {
+            final ChannelOptions options = new ChannelOptions();
+            options.params = Map.of("rewind", "10");
+            final Channel channel = realtime.channels.get(testChannelName, options);
+            final CompletionWaiter completionWaiter = new CompletionWaiter();
+            final AtomicInteger counter = new AtomicInteger();
+
+            channel.subscribe(message -> {
+                int value = counter.incrementAndGet();
+                if (value == 3) completionWaiter.onSuccess();
+            });
+
+            completionWaiter.waitFor();
+
+            assertEquals("Should be exactly 3 messages",3, counter.get());
+
+            Thread.sleep(1500);
+
+            assertEquals("Should be exactly 3 messages even after 1.5 sec wait",3, counter.get());
+        }
+    }
+
 }