Ensure onload callbacks scheduled during or after load are still executed

panel/io/server.py

@@ -139,6 +139,8 @@ def _eval_panel(
  """)
  )
 
+ doc.on_event('document_ready', partial(state._schedule_on_load, doc))
+
  # Set up instrumentation for logging sessions
  logger.info(LOG_SESSION_LAUNCHING, id(doc))
  def _log_session_destroyed(session_context):
@@ -771,6 +773,8 @@ def modify_document(self, doc: 'Document'):
 
  logger.info(LOG_SESSION_LAUNCHING, id(doc))
 
+ doc.on_event('document_ready', partial(state._schedule_on_load, doc))
+
  if config.autoreload:
  path = self._runner.path
  argv = self._runner._argv

panel/io/state.py

@@ -376,22 +376,24 @@ def _schedule_on_load(self, doc: Document, event) -> None:
 
  def _on_load(self, doc: Optional[Document] = None) -> None:
  doc = doc or self.curdoc
- callbacks = self._onload.pop(doc, [])
- if not callbacks:
+ if doc not in self._onload:
  self._loaded[doc] = True
  return
 
  from ..config import config
  from .profile import profile_ctx
  with set_curdoc(doc):
  if (doc and doc in self._launching) or not config.profiler:
- for cb, threaded in callbacks:
- self.execute(cb, schedule='thread' if threaded else False)
+ while doc in self._onload:
+ for cb, threaded in self._onload.pop(doc):
+ self.execute(cb, schedule='thread' if threaded else False)
+ self._loaded[doc] = True
  return
 
  with profile_ctx(config.profiler) as sessions:
- for cb, threaded in callbacks:
- self.execute(cb, schedule='thread' if threaded else False)
+ while doc in self._onload:
+ for cb, threaded in self._onload.pop(doc):
+ self.execute(cb, schedule='thread' if threaded else False)
  path = doc.session_context.request.path
  self._profiles[(path+':on_load', config.profiler)] += sessions
  self.param.trigger('_profiles')
@@ -680,7 +682,7 @@ def onload(self, callback: Callable[[], None | Awaitable[None]] | Coroutine[Any,
  threaded: bool
  Whether the onload callback can be threaded
  """
- if self.curdoc is None or self._is_pyodide:
+ if self.curdoc is None or self._is_pyodide or self.loaded:
  if self._thread_pool:
  future = self._thread_pool.submit(partial(self.execute, callback, schedule=False))
  future.add_done_callback(self._handle_future_exception)
@@ -689,10 +691,6 @@ def onload(self, callback: Callable[[], None | Awaitable[None]] | Coroutine[Any,
  return
  elif self.curdoc not in self._onload:
  self._onload[self.curdoc] = []
- try:
- self.curdoc.on_event('document_ready', partial(self._schedule_on_load, self.curdoc))
- except AttributeError:
- pass # Document already cleaned up
  self._onload[self.curdoc].append((callback, threaded))
 
  def on_session_created(self, callback: Callable[[BokehSessionContext], None]) -> None:

panel/tests/test_server.py

@@ -480,6 +480,56 @@ def test_serve_can_serve_bokeh_app_from_file():
  assert "/bk-app" in server._tornado.applications
 
 
+def test_server_on_load_after_init(threads, port):
+ loaded = []
+
+ def cb():
+ loaded.append(state.loaded)
+
+ def cb2():
+ state.execute(cb, schedule=True)
+
+ def app():
+ state.onload(cb)
+ state.onload(cb2)
+ # Simulate rendering
+ def loaded():
+ state.curdoc
+ state._schedule_on_load(state.curdoc, None)
+ state.execute(loaded, schedule=True)
+ return 'App'
+
+ serve_and_request(app)
+
+ # Checks whether onload callback was executed twice once before and once after load
+ wait_until(lambda: loaded == [False, True])
+
+
+def test_server_on_load_during_load(threads, port):
+ loaded = []
+
+ def cb():
+ loaded.append(state.loaded)
+
+ def cb2():
+ state.onload(cb)
+
+ def app():
+ state.onload(cb)
+ state.onload(cb2)
+ # Simulate rendering
+ def loaded():
+ state.curdoc
+ state._schedule_on_load(state.curdoc, None)
+ state.execute(loaded, schedule=True)
+ return 'App'
+
+ serve_and_request(app)
+
+ # Checks whether onload callback was executed twice once before and once during load
+ wait_until(lambda: loaded == [False, False])
+
+
 def test_server_thread_pool_on_load(threads, port):
  counts = []