Fix crash in vote_last_response when state is None after clear_history#3852
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Chessing234 wants to merge 1 commit intolm-sys:mainfrom
Open
Fix crash in vote_last_response when state is None after clear_history#3852Chessing234 wants to merge 1 commit intolm-sys:mainfrom
Chessing234 wants to merge 1 commit intolm-sys:mainfrom
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`clear_history` resets the Gradio state to `None` (see line 339). If a user clicks an upvote / downvote / flag button before the UI finishes updating, the stale button click runs `vote_last_response` with `state=None`, which then hits `state.dict()` and raises `AttributeError: 'NoneType' object has no attribute 'dict'`. Guard the function with an early return when `state` is `None` so the no-op path is safe; the button-disable behaviour from the caller (`upvote_last_response` etc.) is unaffected. Closes lm-sys#3787.
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Bug
vote_last_responseinfastchat/serve/gradio_web_server.pyunconditionally callsstate.dict(), butstatecan beNone. Reported in #3787.Root cause
clear_historyexplicitly resets the Gradio state:```python
def clear_history(request: gr.Request):
...
state = None
return (state, [], "") + (disable_btn,) * 5
```
The vote buttons are disabled as part of that return, but the UI update is asynchronous in Gradio. If a user clicks upvote / downvote / flag between `clear_history` firing and the button-disable reaching the browser, the stale event runs `vote_last_response(None, ...)`, hitting `state.dict()` and raising `AttributeError: 'NoneType' object has no attribute 'dict'`.
Fix
Early-return from `vote_last_response` when `state is None`. The callers (`upvote_last_response`, `downvote_last_response`, `flag_last_response`) ignore its return value, so a no-op is safe and they still return the same `disable_btn` tuple as before.
Fixes #3787.