rtc: add (*LocalPublication).wait_for_subscriber() (#238)

Co-authored-by: Théo Monnom <[email protected]>

Author: nbsp

livekit-rtc/livekit/rtc/room.py

@@ -288,6 +288,7 @@ def _on_room_event(self, event: proto_room.RoomEvent):
         elif which == "local_track_subscribed":
             sid = event.local_track_subscribed.track_sid
             lpublication = self.local_participant.track_publications[sid]
+            lpublication._first_subscription.set_result(None)
             self.emit("local_track_subscribed", lpublication.track)
         elif which == "track_published":
             rparticipant = self.remote_participants[

livekit-rtc/livekit/rtc/track_publication.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from typing import Optional
+import asyncio
 
 from ._ffi_client import FfiHandle, FfiClient
 from ._proto import e2ee_pb2 as proto_e2ee
@@ -71,6 +72,10 @@ def encryption_type(self) -> proto_e2ee.EncryptionType.ValueType:
 class LocalTrackPublication(TrackPublication):
     def __init__(self, owned_info: proto_track.OwnedTrackPublication):
         super().__init__(owned_info)
+        self._first_subscription: asyncio.Future[None] = asyncio.Future()
+
+    async def wait_for_subscription(self) -> None:
+        await asyncio.shield(self._first_subscription)
 
 
 class RemoteTrackPublication(TrackPublication):