WS connection close can cause render exception

[Archmonger]

Old Behavior

If the webpage is closed or refreshed prior to component load, an exception will occur.

2021-10-16T22:57:18-0700 | ERROR | Failed to render Button(2992041646976, websocket=WebsocketConnection(scope={'type': 'websocket', 'path': '/_idom/websocket/test_app.components.Button/', 'raw_path': b'/_idom/websocket/test_app.components.Button/', 'headers': [(b'host', b'127.0.0.1:8000'), (b'connection', b'Upgrade'), (b'pragma', b'no-cache'), (b'cache-control', b'no-cache'), (b'upgrade', b'websocket'), (b'origin', b'http://127.0.0.1:8000'), (b'sec-websocket-version', b'13'), (b'user-agent', b'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like 
Gecko) Chrome/94.0.4606.81 Safari/537.36'), (b'accept-encoding', b'gzip, deflate, br'), (b'accept-language', b'en'), (b'cookie', b'csrftoken=jzHH9Te6cml6zXxOwjSkdsMupUjoIPPLGkNGMvCsyUsdidzNmYJNBFWeflJI59Qe; sessionid=1t95jxh44o9a1zfzcgsamlhau1mxjilj'), (b'sec-gpc', b'1'), (b'sec-websocket-key', b'd5LydM5OiDLcAgSqam7GcQ=='), (b'sec-websocket-extensions', b'permessage-deflate; client_max_window_bits')], 'query_string': b'kwargs=%7B%7D', 'client': ['127.0.0.1', 52403], 'server': ['127.0.0.1', 8000], 'subprotocols': [], 'asgi': {'version': '3.0'}, 'cookies': {'csrftoken': 'jzHH9Te6cml6zXxOwjSkdsMupUjoIPPLGkNGMvCsyUsdidzNmYJNBFWeflJI59Qe', 'sessionid': '1t95jxh44o9a1zfzcgsamlhau1mxjilj'}, 'session': <django.utils.functional.LazyObject object at 0x000002B8A39433A0>, 'user': <channels.auth.UserLazyObject object at 0x000002B8A3943CA0>, 'path_remaining': '', 'url_route': {'args': (), 'kwargs': {'view_id': 'test_app.components.Button'}}}, close=<bound method AsyncWebsocketConsumer.close of <django_idom.websocket_consumer.IdomAsyncWebsocketConsumer object at 0x000002B8A3943E50>>, disconnect=<bound method IdomAsyncWebsocketConsumer.disconnect of <django_idom.websocket_consumer.IdomAsyncWebsocketConsumer object at 0x000002B8A3943E50>>, view_id='test_app.components.Button'))
Traceback (most recent call last):
  File "C:\Users\username\Documents\Repositories\django-idom\.venv\lib\site-packages\idom\core\layout.py", line 207, in _render_component
    self._render_model(old_state, new_state, raw_model)
  File "C:\Users\username\Documents\Repositories\django-idom\.venv\lib\site-packages\idom\core\layout.py", line 245, in _render_model
    self._render_model_children(old_state, new_state, raw_model.get("children", []))
  File "C:\Users\username\Documents\Repositories\django-idom\.venv\lib\site-packages\idom\core\layout.py", line 364, in _render_model_children
    self._render_model(old_child_state, new_child_state, child)
  File "C:\Users\username\Documents\Repositories\django-idom\.venv\lib\site-packages\idom\core\layout.py", line 244, in _render_model
    self._render_model_attributes(old_state, new_state, raw_model)
  File "C:\Users\username\Documents\Repositories\django-idom\.venv\lib\site-packages\idom\core\layout.py", line 266, in _render_model_attributes
    self._render_model_event_handlers_without_old_state(
  File "C:\Users\username\Documents\Repositories\django-idom\.venv\lib\site-packages\idom\core\layout.py", line 306, in _render_model_event_handlers_without_old_state
    self._event_handlers[target] = handler
AttributeError: _event_handlers

New Behavior

Need to gracefully handle WS close within _render_model

Implementation Details

No response

Code of Conduct

• I agree to follow the Code of Conduct.

[Archmonger]

@rmorshea What do you think about moving this issue to core?

[rmorshea]

That seems right to me.

[rmorshea]

Do we know if this still happens though?

[Archmonger]

I'll check.

[Archmonger]

I wasn't able to replicate this with IDOM v0.43.0.

Closing issue.