io::copy: don't poll the reader again after eof while waiting for the writer to flush #894
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yoshuawuyts
approved these changes
Oct 15, 2020
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@jbr Could you add a test for this, with some artificially constructed futures? The artificial read future can panic if it gets polled after EOF. |
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Confirmed locally that the test does in fact fail with the changes to async_std::io::copy stashed |
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I do think it's worth figuring out if this was a bug previous to this commit. It was unspecified in documentation, and it's unclear if someone might be relying on the "continues to poll after eof" behavior, although that seems unlikely. I think this change is worth making either way, but the question is whether it's a breaking change or a bugfix |
joshtriplett
approved these changes
Jun 20, 2022
Fishrock123
approved these changes
Jun 20, 2022
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I'm not entirely sure if this is a bug or just unexpected behavior, but I thought I'd write a quick PR just in case. Prior to this PR, io::copy continues to poll the reader after it has already returned
Poll::Ready(Ok(0))in the situation where the writer's flush is not immediately Ready. This resulted in a bug with a Read implementation that expected not to be read again after it returned eof. Removing the after-eof polling might save someone else from some confusion