Fix onload handling in pyodide

panel/io/pyodide.py

@@ -358,6 +358,7 @@ def pysync(event):
 
     try:
         pydoc.unhold()
+        pydoc.on_event('document_ready', functools.partial(state._schedule_on_load, pydoc))
         pydoc.callbacks.trigger_event(DocumentReady())
     except Exception as e:
         print(f'Error raised while processing Document events: {e}')  # noqa: T201
@@ -389,6 +390,7 @@ def pysync(event):
 
     doc.on_change(pysync)
     doc.unhold()
+    doc.on_event('document_ready', functools.partial(state._schedule_on_load, doc))
     doc.callbacks.trigger_event(DocumentReady())
 
 async def _link_model(ref: str, doc: Document) -> None:

panel/tests/ui/io/test_convert.py

@@ -112,6 +112,19 @@ def on_click(e):
 pn.Row('Output').servable();
 """
 
+onload_app = """
+import panel as pn
+
+row = pn.Row('Foo')
+
+def onload():
+    row[:] = ['Bar']
+
+pn.state.onload(onload)
+
+row.servable()
+"""
+
 
 @pytest.fixture(scope="module")
 def http_serve():
@@ -264,3 +277,12 @@ def test_pyodide_test_convert_png_app(http_serve, page, runtime):
     expect(page.locator('img')).to_have_count(1)
 
     assert [msg for msg in msgs if msg.type == 'error' and 'favicon' not in msg.location['url']] == []
+
+
+@pytest.mark.parametrize('runtime', ['pyodide', 'pyodide-worker'])
+def test_pyodide_test_convert_onload_app(http_serve, page, runtime):
+    msgs = wait_for_app(http_serve, onload_app, page, runtime)
+
+    expect(page.locator('.markdown')).to_have_text('Bar')
+
+    assert [msg for msg in msgs if msg.type == 'error' and 'favicon' not in msg.location['url']] == []