util: add a channel body

[cratelyn]

this branch represents a revival of #100, applying changes that were suggested in review. in particular, see 08aba95 and 4fed62f.

changes

use sync::oneshot for error channel

this commit refactors the channel-backed body in #100, changing the
mpsc::Receiver<E> used to transmit an error into a
oneshot::Receiver<E>.

this should improve memory usage, and make the channel a smaller
structure.

in order to achieve this, some minor adjustments are made:

• use pin projection, projecting pinnedness to the oneshot receiver,
  polling it via core::future::Future::poll(..) to yield a body frame.

• add Debug bounds were needed.

use &mut self method receivers

this commit refactors the channel-backed body in #100, changing the
signature of send_* methods on the sender to require a mutable
reference.

[cratelyn]

the msrv action failed here: https://github.com/hyperium/http-body/actions/runs/12635582609/job/35249835531

the relevant bit of our manifest getting in the way is the dep: prefix syntax, noted as being available only after rust 1.60. see the cargo book here: https://doc.rust-lang.org/cargo/reference/features.html#optional-dependencies

4a5b234 removes this syntax, to be backwards compatible with older rust versions.

[cratelyn]

ah, i just saw that #128 was merged yesterday. i've rebased on top of that, so we can use the dep: syntax in conditional dependencies. nice!

[seanmonstar]

Thanks for reviving this! I'm excited to see it happen. One thought inline.

[cratelyn]

i see the MRSV listed in http-body-util's Cargo.toml as 1.61, here. #128 seems to imply that the MSRV is 1.61.

conversely, the logs in the failing action above mention using the 1.49 toolchain, here:

running `rustup toolchain add 1.49 --no-self-update`

my understanding is that this is because #128 did not update the rust-version field in the http-body crate. see:

http-body/http-body/Cargo.toml

Line 26 in 98d0886

rust-version = "1.49"

do you have a preference between: (a) respecting a 1.49 MSRV, restoring the changes in the commit mentioned above, or (b) updating the MSRV of http-body to match http-body-util, and keeping the dep: syntax?

[seanmonstar]

Ah, interesting. I think that's happened is that cargo hack will check both MSRV versions set, but the error noticed here is because even though it's only compiling http-body, it has the to parse the whole workspace of Cargo.tomls, and it doesn't understand the one in http-body-util. Whereas the actual Rust code isn't compiled in that step, so it works when moving on to check the util crate.

I'm fine with making the http-body MSRV be whatever the minimum is needed to understad dep: syntax.

[cratelyn]

i've opened #141, which updates the MSRV, and rebased the commits in this PR to be based upon that change. i've also confirmed locally that cargo hack --rust-version --no-dev-deps check works as expected.

thanks for your help reviewing this, i am very excited to get this over the finish line. 🙂 🏁

[cratelyn]

♻️ ...and now rebased on master now that #141 is merged!

[seanmonstar]

Nice!