async-multipart: impl Stream for Multipart<Bytes>

[shikhar]

This allows for zero-copy when using hyper with https://docs.rs/hyper/0.14.10/hyper/struct.Body.html#method.wrap_stream

[Jake-Shadle]

Apologies, forgot about this PR, will take a look now!

[shikhar]

Looks like the set of lints needs an upgrade from v0.3 to v0.4 EmbarkStudios/rust-ecosystem#59

[Jake-Shadle]

Yes, I've just pushed that, just need a rebase and this PR should be good.

[Jake-Shadle]

Thanks for the PR, sorry it took so long to look at it!

[Jake-Shadle]

So I realized that after I merged this that this change doesn't actually affect usage of the Multipart stream, as they are only ever sent, not received, which is what the Stream impl is for. I don't think it has a negative impact on the library so I don't think there is any harm in keeping it, and I'll add it to the CHANGELOG, but don't think this change alone warrants a release. Unless I have missed something?

[shikhar]

Hey @Jake-Shadle I'm fine with no imminent release for this, since I'm able to use a git dependency.

So I realized that after I merged this that this change doesn't actually affect usage of the Multipart stream, as they are only ever sent, not received, which is what the Stream impl is for.

Hmm, I am indeed using this new impl for sending. I have in-memory data to be uploaded and when I call Object::insert_multipart() with content: Bytes, I get Multipart<Bytes>. In order to create a hyper Body, without this change the only way to get the multipart data out is to rely on the Read / AsyncRead impls which involve copying, but the underlying data is all represented as Bytes and having this Stream impl avoids copying. With hyper it is especially convenient since I am able to use https://docs.rs/hyper/0.14.12/hyper/struct.Body.html#method.wrap_stream

[Jake-Shadle]

Ahh ok, thanks for clarifying, I just glanced at the docs which seem to say the inverse.