Refactor backoff handling and improve test wait time for compatibility

- Updated backoff handling logic in the GossipSub class to always add backoff, regardless of topic presence in the mesh.
- Adjusted the wait time in the test_handle_prune function to 0.5 seconds for better compatibility on Windows systems.

Author: yashksaini-coder

libp2p/pubsub/gossipsub.py

@@ -1085,12 +1085,14 @@ async def handle_prune(
             px_peers.append(peer)
 
         # Remove peer from mesh for topic
-        if topic in self.mesh:
-            if backoff_till > 0:
-                self._add_back_off(sender_peer_id, topic, False, backoff_till)
-            else:
-                self._add_back_off(sender_peer_id, topic, False)
+        # Always add backoff, even if topic is not currently in mesh
+        if backoff_till > 0:
+            self._add_back_off(sender_peer_id, topic, False, backoff_till)
+        else:
+            self._add_back_off(sender_peer_id, topic, False)
 
+        # Remove sender from mesh if topic exists in mesh
+        if topic in self.mesh:
             self.mesh[topic].discard(sender_peer_id)
             if self.scorer is not None:
                 self.scorer.on_leave_mesh(sender_peer_id, topic)

tests/core/pubsub/test_gossipsub.py

@@ -207,8 +207,8 @@ async def test_handle_prune():
 
         # NOTE: We increase `heartbeat_interval` to 3 seconds so that bob will not
         # add alice back to his mesh after heartbeat.
-        # Wait for bob to `handle_prune`
-        await trio.sleep(0.1)
+        # Wait for bob to `handle_prune` - increased wait time for Windows compatibility
+        await trio.sleep(0.5)
 
         # Check that alice is no longer bob's mesh peer
         assert id_alice not in gossipsubs[index_bob].mesh[topic]