Ensure no events are dispatched before the websocket is open (#6528)

panel/chat/feed.py

@@ -26,7 +26,6 @@
 from ..layout.card import Card
 from ..layout.spacer import VSpacer
 from ..pane.image import SVG
-from ..widgets.button import Button
 from .message import ChatMessage
 
 if TYPE_CHECKING:
@@ -181,6 +180,8 @@ class ChatFeed(ListPanel):
     _callback_state = param.ObjectSelector(objects=list(CallbackState), doc="""
         The current state of the callback.""")
 
+    _callback_trigger = param.Event(doc="Triggers the callback to respond.")
+
     _disabled_stack = param.List(doc="""
         The previous disabled state of the feed.""")
 
@@ -260,8 +261,7 @@ def __init__(self, *objects, **params):
         )
 
         # handle async callbacks using this trick
-        self._callback_trigger = Button(visible=False)
-        self._callback_trigger.on_click(self._prepare_response)
+        self.param.watch(self._prepare_response, '_callback_trigger')
 
     def _get_model(
         self, doc: Document, root: Model | None = None,
@@ -491,7 +491,7 @@ async def _handle_callback(self, message, loop: asyncio.BaseEventLoop):
             response = await asyncio.to_thread(self.callback, *callback_args)
         await self._serialize_response(response)
 
-    async def _prepare_response(self, _) -> None:
+    async def _prepare_response(self, *_) -> None:
         """
         Prepares the response by scheduling the placeholder and
         executing the callback.
@@ -656,7 +656,7 @@ def respond(self):
         """
         Executes the callback with the latest message in the chat log.
         """
-        self._callback_trigger.param.trigger("clicks")
+        self.param.trigger("_callback_trigger")
 
     def stop(self) -> bool:
         """

panel/io/state.py

@@ -268,7 +268,7 @@ def _thread_id(self, thread_id: int) -> None:
             self._thread_id_[self.curdoc] = thread_id
 
     def _unblocked(self, doc: Document) -> bool:
-        return doc is self.curdoc and self._thread_id in (self._current_thread, None)
+        return doc is self.curdoc and self._thread_id in (self._current_thread, None) and (not doc.session_context or self._loaded.get(doc))
 
     @param.depends('_busy_counter', watch=True)
     def _update_busy_counter(self):

panel/tests/test_server.py

@@ -291,6 +291,9 @@ async def cb(count=[0]):
     def app():
         button = Button(name='Click')
         state.add_periodic_callback(cb, 100)
+        def loaded():
+            state._schedule_on_load(state.curdoc, None)
+        state.execute(loaded, schedule=True)
         return button
 
     serve_and_request(app)
@@ -715,6 +718,9 @@ def cb(count=[0]):
     def app():
         button = Button(name='Click')
         state.add_periodic_callback(cb, 100)
+        def loaded():
+            state._schedule_on_load(state.curdoc, None)
+        state.execute(loaded, schedule=True)
         return button
 
     serve_and_request(app)