feat(util): introduce a "fused" body combinator#145
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this commit introduces a new `Body` combinator to the `http-body-util` library, `http_body_util::combinators::Fuse<B>`. this combinator is roughly equivalent to the `std::iter::Fuse<I>` iterator, which returns `None` after the inner iterator returns it once. while bodies *should* return `Poll::Ready(None)` indefinitely after reaching the end of the stream or returning an error, this combinator can help prevent further polling of an underlying body implementation, in the same manner that `std::iter::Iterator::fuse()` helps prevent an underlying iterator that might e.g. yield `Some(value)` after yielding `None`, or panic. Signed-off-by: katelyn martin <me+cratelyn@katelyn.world>
cratelyn
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| fn is_end_stream(&self) -> bool { | ||
| self.inner.is_none() | ||
| } | ||
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| fn size_hint(&self) -> SizeHint { | ||
| self.inner | ||
| .as_ref() | ||
| .map(B::size_hint) | ||
| .unwrap_or_else(|| SizeHint::with_exact(0)) | ||
| } |
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i found myself wishing for this recently, since this pull request was opened.
besides the panic avoidance that this middleware can offer in certain situations, should the inner body not accept repeated polling after yielding a Ready(None) or Ready(Some(Err(_))), this middleware offers a nice additional benefit: it provides an accurate is_end_stream() for inner bodies that use the default implementation of this trait method, which always returns false.
seanmonstar
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Looks excellent to me! Thanks for the thorough docs and tests too! <3
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this commit introduces a new
Bodycombinator to thehttp-body-utillibrary,http_body_util::combinators::Fuse<B>.this combinator is roughly equivalent to the
std::iter::Fuse<I>iterator, which returnsNoneafter the inner iterator returns it once.while bodies should return
Poll::Ready(None)indefinitely after reaching the end of the stream or returning an error, this combinator can help prevent further polling of an underlying body implementation, in the same manner thatstd::iter::Iterator::fuse()helps prevent an underlying iterator that might e.g. yieldSome(value)after yieldingNone, or panic.