web-transport-wasm

A wrapper around the WebTransport browser API.

Poll and async

The browser API is a set of promises, but the surface here is a state machine. Every operation is a poll_* method that a caller steps from its own loop, with the async methods as thin wrappers over them. That is what implements web-transport-trait's poll module, so a sans-I/O caller needs no adapter, and it is what makes an abandoned operation safe: the promise stays subscribed, so a chunk or an accepted stream is never dropped on the floor between polls.

Clone the Session to run operations concurrently. Each clone keeps its own in-flight operation, while the underlying browser stream locks are shared — a browser stream can only be locked once.

Testing

CI only compiles this crate: the browser API it wraps exists nowhere else, so the poll paths have no automated coverage. just harness builds a browser harness and the QUIC peer that drives it, then serves the page for a browser to open. It exercises accept, a peer reset code, closed-watches racing buffered bytes, datagrams, and a session close, and reports a row per check.

Requirements

web-sys still gates the WebTransport bindings behind --cfg=web_sys_unstable_apis, so this crate cannot compile without it. The flag can't be enabled by a dependency; it has to come from the final build. Add it to .cargo/config.toml:

[build]
rustflags = ["--cfg=web_sys_unstable_apis"]
rustdocflags = ["--cfg=web_sys_unstable_apis"]

rustdocflags is separate because rustdoc does not inherit rustflags; without it cargo doc and doctests fail even though cargo build succeeds.

Or set RUSTFLAGS="--cfg=web_sys_unstable_apis" and RUSTDOCFLAGS="--cfg=web_sys_unstable_apis" in the environment. Both override .cargo/config.toml rather than adding to it, so use one or the other.

Building without the flag fails with a compile_error! pointing back here.