Fix and add test for multiple subscribers to same topic

rosbridge_library/src/rosbridge_library/internal/subscribers.py

@@ -206,7 +206,7 @@ def _new_sub_callback(self, msg):
         subscriptors.
         """
         with self.lock:
-            self.callback(msg, [self.new_subscriptions.values()])
+            self.callback(msg, self.new_subscriptions.values())
             self.subscriptions.update(self.new_subscriptions)
             self.new_subscriptions = {}
             self.node_handle.destroy_subscription(self.new_subscriber)

rosbridge_server/test/websocket/multiple_subscribers.test.py

@@ -0,0 +1,63 @@
+import os
+import sys
+import unittest
+
+from rclpy.node import Node
+from std_msgs.msg import String
+from twisted.python import log
+
+sys.path.append(os.path.dirname(__file__))  # enable importing from common.py in this directory
+
+import common  # noqa: E402
+from common import expect_messages, sleep, websocket_test  # noqa: E402
+
+log.startLogging(sys.stderr)
+
+generate_test_description = common.generate_test_description
+
+
+class TestMultipleSubscribers(unittest.TestCase):
+    @websocket_test
+    async def test_multiple_subscribers(self, node: Node, make_client):
+        ws_client1 = await make_client()
+        ws_client1.sendJson(
+            {
+                "op": "subscribe",
+                "topic": "/a_topic",
+                "type": "std_msgs/String",
+            }
+        )
+
+        ws_client2 = await make_client()
+        ws_client2.sendJson(
+            {
+                "op": "subscribe",
+                "topic": "/a_topic",
+                "type": "std_msgs/String",
+            }
+        )
+
+        ws1_completed_future, ws_client1.message_handler = expect_messages(
+            1, "WebSocket 1", node.get_logger()
+        )
+        ws1_completed_future.add_done_callback(lambda _: node.executor.wake())
+        ws2_completed_future, ws_client2.message_handler = expect_messages(
+            1, "WebSocket 2", node.get_logger()
+        )
+        ws2_completed_future.add_done_callback(lambda _: node.executor.wake())
+
+        pub_a = node.create_publisher(String, "/a_topic", 1)
+
+        await sleep(node, 1)
+
+        pub_a.publish(String(data="hello"))
+
+        self.assertEqual(
+            await ws1_completed_future,
+            [{"op": "publish", "topic": "/a_topic", "msg": {"data": "hello"}}],
+        )
+        self.assertEqual(
+            await ws2_completed_future,
+            [{"op": "publish", "topic": "/a_topic", "msg": {"data": "hello"}}],
+        )
+        node.destroy_publisher(pub_a)