wasm-ext: WebTransport

[mriise]

Description

Add WebTransport support for wasm targets. Similar to the discussion in #3611, this should be done with the web-sys crate.

Requirements

1. Get a new version of web-sys published (Bump versions rustwasm/wasm-bindgen#3400), the bindings were added a while ago in Add WebTransport webidl to unstable rustwasm/wasm-bindgen#3344 but haven't been published yet.
2. Add a new transport crate (libp2p-websys-webtransport?) and implementation.
3. Test compatibility with go-libp2p's webtransport implementation.

Open questions

• WebTransport is an unstable api for web-sys, do we pass this into build script or just add as note and have users pass the flag?

Are you planning to do it yourself in a pull request?

Yes

[mriise]

Unfortunately I am blocked doing any implementation until the web-sys version update as rust will scream violently that you cant link 2 different versions of wasm-bindgen-shared in the same package. In theory the workaround is to patch everything (this includes forking getrandom to patch) but that's a bit much...

Will do so if the ver bump takes too long though...

[thomaseizinger]

Would love to see libp2p-websys-webtransport!

The linked PR is not a breaking change, meaning you should be able to (temporarily) use [patch.crates-io] in our workspace manifest to redirect wasm-bindgen-shared to a Git dependency.

That at least allows us to see a passing CI apart from the cargo deny check that will flag your Git dependency :)

[thomaseizinger]

WebTransport is an unstable api for web-sys, do we pass this into build script or just add as note and have users pass the flag?

We can't make that decision for our users. If they have web-sys in their dependency tree, us activating that flag could result in breaking changes for them. I'd suggest that we release it as an alpha and not expose it via the meta-crate, similar to how we are currently dealing with webrtc and quic.

Users then need to depend in it separately and we can document that they need to set this special cfg for things to work.

[mriise]

The linked PR is not a breaking change, meaning you should be able to (temporarily) use [patch.crates-io] in our workspace manifest to redirect wasm-bindgen-shared to a Git dependency.

Figured out I was putting the patch in the local crate level when it needed to be at the workspace level. Things are building now :)

[thomaseizinger]

The linked PR is not a breaking change, meaning you should be able to (temporarily) use [patch.crates-io] in our workspace manifest to redirect wasm-bindgen-shared to a Git dependency.

Figured out I was putting the patch in the local crate level when it needed to be at the workspace level. Things are building now :)

Neat! Feel free to open a draft PR.

[Jorropo]

Somewhat related, I got a PoC of this working in go-libp2p libp2p/go-libp2p#2191 this was way easier than I expected and took half a day (the stream api maps fairly well maps to go's io.ReadWriteCloser).
I might try the same here if no one pickups this just to get an excuse to write some rust.

[mxinden]

@Jorropo in case you want to work on this, you can build on top of #3846.