fix: report error code 80017 for a closed connection

lib/src/main/java/io/ably/lib/transport/ConnectionManager.java

@@ -72,7 +72,7 @@ public class ConnectionManager implements ConnectListener {
      * default errors
      ***********************************/
 
-    static ErrorInfo REASON_CLOSED = new ErrorInfo("Can't attach when not in an active state", 200, 10000);
+    static ErrorInfo REASON_CLOSED = new ErrorInfo("Connection closed", 400, 80017);
     static ErrorInfo REASON_DISCONNECTED = new ErrorInfo("Connection temporarily unavailable", 503, 80003);
     static ErrorInfo REASON_SUSPENDED = new ErrorInfo("Connection unavailable", 503, 80002);
     static ErrorInfo REASON_FAILED = new ErrorInfo("Connection failed", 400, 80000);

lib/src/test/java/io/ably/lib/transport/ConnectionManagerClosedErrorTest.java

@@ -0,0 +1,59 @@
+package io.ably.lib.transport;
+
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.notNullValue;
+import static org.junit.Assert.assertThat;
+
+import io.ably.lib.debug.DebugOptions;
+import io.ably.lib.realtime.AblyRealtime;
+import io.ably.lib.realtime.CompletionListener;
+import io.ably.lib.realtime.ConnectionState;
+import io.ably.lib.test.common.Helpers;
+import io.ably.lib.test.util.MockWebsocketFactory;
+import io.ably.lib.types.AblyException;
+import io.ably.lib.types.ErrorInfo;
+import java.util.concurrent.atomic.AtomicReference;
+import org.junit.Test;
+
+public class ConnectionManagerClosedErrorTest {
+
+    /**
+     * Closing the connection reports Ably code 80017 with HTTP status code 400, both in the
+     * state change and when attaching a channel afterwards.
+     */
+    @Test
+    public void closed_connection_error_codes() throws AblyException {
+        DebugOptions options = new DebugOptions("appid.keyid:keysecret");
+        options.autoConnect = false;
+        MockWebsocketFactory mockTransport = new MockWebsocketFactory();
+        mockTransport.failConnect();
+        options.transportFactory = mockTransport;
+
+        try (AblyRealtime ably = new AblyRealtime(options)) {
+            Helpers.ConnectionWaiter connectionWaiter = new Helpers.ConnectionWaiter(ably.connection);
+            ably.connection.connect();
+            assertThat(connectionWaiter.waitFor(ConnectionState.disconnected, 1, 10000), is(true));
+            ably.connection.close();
+            assertThat(connectionWaiter.waitFor(ConnectionState.closed, 1, 10000), is(true));
+
+            ErrorInfo closedReason = connectionWaiter.lastStateChange().reason;
+            assertThat(closedReason, is(notNullValue()));
+            assertThat(closedReason.code, is(80017));
+            assertThat(closedReason.statusCode, is(400));
+
+            AtomicReference<ErrorInfo> attachError = new AtomicReference<>();
+            ably.channels.get("closed_connection_attach").attach(new CompletionListener() {
+                @Override
+                public void onSuccess() {}
+
+                @Override
+                public void onError(ErrorInfo reason) {
+                    attachError.set(reason);
+                }
+            });
+            assertThat(attachError.get(), is(notNullValue()));
+            assertThat(attachError.get().code, is(80017));
+            assertThat(attachError.get().statusCode, is(400));
+        }
+    }
+}