Detached model state on render of unmounted context consumer where context provider value does not change.

[Archmonger]

Current Situation

Context should be able to be scoped to conditionally rendered components, and when those subcomponents are removed the deletion of the Context should be handled gracefully.

See: https://github.com/Archmonger/Conreq/blob/d64b3ba879d263b36ab4806d4790d44cefea1045/conreq/_core/components.py#L46-L64

Traceback (most recent call last):
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\django\contrib\staticfiles\handlers.py", line 101, in __call__
    return await self.application(scope, receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\routing.py", line 62, in __call__
    return await application(scope, receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\security\websocket.py", line 37, in __call__
    return await self.application(scope, receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\sessions.py", line 47, in __call__
    return await self.inner(dict(scope, cookies=cookies), receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\sessions.py", line 263, in __call__
    return await self.inner(wrapper.scope, receive, wrapper.send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\sessions.py", line 47, in __call__
    return await self.inner(dict(scope, cookies=cookies), receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\sessions.py", line 263, in __call__
    return await self.inner(wrapper.scope, receive, wrapper.send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\auth.py", line 185, in __call__
    return await super().__call__(scope, receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\middleware.py", line 24, in __call__
    return await self.inner(scope, receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\routing.py", line 116, in __call__
    return await application(
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\consumer.py", line 94, in app
    return await consumer(scope, receive, send)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\consumer.py", line 62, in __call__
    await await_many_dispatch([receive], self.dispatch)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\utils.py", line 50, in await_many_dispatch
    await dispatch(result)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\consumer.py", line 73, in dispatch
    await handler(message)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\channels\generic\websocket.py", line 238, in websocket_disconnect
    await self.disconnect(message["code"])
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\django_idom\websocket\consumer.py", line 42, in disconnect
    await self._idom_dispatcher_future
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\django_idom\websocket\consumer.py", line 76, in _run_dispatch_loop
    await serve_json_patch(
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\serve.py", line 44, in serve_json_patch
    async with create_task_group() as task_group:
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\anyio\_backends\_asyncio.py", line 662, in __aexit__
    raise exceptions[0]
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\serve.py", line 84, in _single_outgoing_loop
    await send(await render_json_patch(layout))
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\serve.py", line 53, in render_json_patch
    return VdomJsonPatch.create_from(await layout.render())
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\layout.py", line 153, in render
    result = await self._debug_render()
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\layout.py", line 142, in render
    return self._create_layout_update(model_state)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\layout.py", line 161, in _create_layout_update
    new_state = _copy_component_model_state(old_state)
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\layout.py", line 528, in _copy_component_model_state
    parent: Optional[_ModelState] = old_model_state.parent
  File "C:\Users\Markg\Documents\Repositories\Conreq\.venv\lib\site-packages\idom\core\layout.py", line 661, in parent
    assert parent is not None, "detached model state"
AssertionError: detached model state

Can be replicated by pulling the latest Conreq branch, and clicking between the any of the "settings" sidebar tabs, then going to a different tab.

Proposed Actions

Determine root cause and fix.

[rmorshea]

I cloned the repo but don't understand how to reproduce. All I see is this when I load up the app:

I see no errors when navigating between tabs.

[Archmonger]

Wanna hop on a call on Saturday for me to demo?

[rmorshea]

I'm away this weekend unfortunately so will have till next week.

[Archmonger]

Okay, the issue should specifically happen if you click on the Settings tab (which has a scoped context), then click off of the tab onto something like App Store.

Based on the screenshot it looks like you cloned the wrong branch.

Needs to be the app_store branch, which is the only branch with IDOM integration.

[Archmonger]

Let me know if you've been able to replicate this on the app_store branch

[rmorshea]

I've had trouble getting it set up. I can't remember the error I was experiencing at the moment. Can try and post later.

[Archmonger]

@rmorshea I can demo today if you are available.

[rmorshea]

I'll be available at 5:30 Pacific Time.

[rmorshea]

Still need to create a reproducible example, but always rendering the whole tree (as suggested in this comment) seems to fix this problem.

[Archmonger]

Closed by #870