Allow calling UnboundedReceiver::try_next after None #2369
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Allow calling `UnboundedReceiver::try_next` and `Receiver::try_next`
after `None`: do not panic.
Not-panicking is equally safe, and does not have negative performance
implication.
It is irrelevant for `Stream` implementation to panic or not (because
`Stream` behavior is unspecified after `None`), but panicking in
`try_next` just complicates the interface: returned `Ok(None)` is
reasonable assumption to have.
Consider this use case: drain the queue on drop by performing
app-specific cleanup of queued messages.
The obvious implementation would be:
```
impl Drop for MyReceiverWrapper {
fn drop(&mut self) {
while let Ok(Some(m)) self.try_next() {
cleanup(m);
}
}
}
```
Without this change, I cannot even say for sure how this code need
to be implemented to avoid panicking. E. g. is `is_closed` enough
or some additional checks need to be performed?
taiki-e
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Mar 1, 2021
stepancheg
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Done. |
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Do not panic.
Not-panicking is equally safe, and does not have negative performance
implication.
It is irrelevant for
Streamimplementation to panic or not (becauseStreambehavior is unspecified afterNone), but panicking intry_nextjust complicates the interface: returnedOk(None)isreasonable assumption to have.
Consider this use case: drain the queue on drop by performing
app-specific cleanup of queued messages.
The obvious implementation would be:
Without this change, I cannot even say for sure how this code need
to be implemented to avoid panicking. E. g. is
is_closedenoughor some additional checks need to be performed?