feat: lazily initialize pause queue in WokwiClient and ensure thread-safe event handling in EventQueue

Author: JakubAndrysek

src/wokwi_client/client.py

@@ -42,7 +42,8 @@ def __init__(self, token: str, server: Optional[str] = None):
         self._transport = Transport(token, server or DEFAULT_WS_URL)
         self.last_pause_nanos = 0
         self._transport.add_event_listener("sim:pause", self._on_pause)
-        self._pause_queue = EventQueue(self._transport, "sim:pause")
+        # Lazily create the pause queue inside the running event loop
+        self._pause_queue: Optional[EventQueue] = None
 
     async def connect(self) -> dict[str, Any]:
         """
@@ -159,6 +160,8 @@ async def wait_until_simulation_time(self, seconds: float) -> None:
         await pause(self._transport)
         remaining_nanos = seconds * 1e9 - self.last_pause_nanos
         if remaining_nanos > 0:
+            if self._pause_queue is None:
+                self._pause_queue = EventQueue(self._transport, "sim:pause")
             self._pause_queue.flush()
             await resume(self._transport, int(remaining_nanos))
             await self._pause_queue.get()

src/wokwi_client/event_queue.py

@@ -23,12 +23,15 @@ class EventQueue:
     """A queue for events from a specific event type."""
 
     def __init__(self, transport: Transport, event_type: str) -> None:
+        # Bind the queue to the current running loop
+        self._loop = asyncio.get_running_loop()
         self._queue: asyncio.Queue[EventMessage] = asyncio.Queue()
         self._transport = transport
         self._event_type = event_type
 
         def listener(event: EventMessage) -> None:
-            self._queue.put_nowait(event)
+            # Ensure put happens on the queue's loop (safe across threads/loops)
+            self._loop.call_soon_threadsafe(self._queue.put_nowait, event)
 
         self._listener = listener
         self._transport.add_event_listener(self._event_type, self._listener)