n0-future

number 0's way of doing async rust.

This crate is supposed to fulfill two purposes:

1. Make it easier to grab one library that re-exposes some sane future/stream combinators that don't use too much unsafe code and seem safe without requiring you to install lots of small libraries.
2. Make it easier to write async code that is Wasm-compatible.

About safer future-related code

We re-expose futures-lite, futures-buffered and futures-util (but mostly for Sink and its combinators). If you're wondering why we're not re-exposing/using X Y or Z, please first read our article about some of our challenges with async rust: https://www.iroh.computer/blog/async-rust-challenges-in-iroh

About easier Wasm-compatible code

Writing code that works in the wasm*-*-unknown targets is not easy:

• std::time::Instant::now() panics on use
• You can't spawn threads
• If you use wasm-bindgen (practically your only option), structs like JsValue are !Send.

We aim to solve these issues by providing similar-looking APIs that are easy to #[cfg(...)] between Wasm and non-wasm targets, ideally not requiring any cfg at all, but instead the cfg-ing is limited to happen inside this library only.

We do this in a couple of ways:

• n0_future::time re-exports tokio::time::Instant and friends natively, but web_time::Instant and friends in Wasm.
• n0_future::task re-exports tokio with its spawn, JoinHandle, JoinSet, Sleep, Timeout, Interval, etc. utilities, but in Wasm re-exports a very similar API that's based on wasm-bindgen-futures.
• Generally, re-exports natively are Send, while re-exports in browsers are !Send. There's quickly a need for utilities such as n0_future::boxed which re-exports Box<dyn Future + Send> natively, but just Box<dyn Future> in Wasm (and the same for Stream).

Scope

It's entirely possible that we'll expand the scope of this library, that currently is mostly a re-exports crate to a crate that provides our own flavor of async APIs that we deem are safer to use, we write about some of these ideas in this issue: https://github.com/n0-computer/iroh/issues/2979

Feature flags

• serde: Enables serde support for the [time::SystemTime] type when building for WebAssembly.

Note to Maintainers: Creating a release

• Make sure to have git-cliff, cargo-release and cargo-semver-checks installed.
• Figure out whether this release is major/minor/patch by running cargo semver-checks check-release --release-type=major/minor/patch and see which one fits
• Use git-cliff to generate the changelog
• Bump the version by major/minor/patch in Cargo.toml and create a release prep PR.
• Run cargo release to check if the release would go through well.
• Run cargo release --execute to run the release

License

Copyright 2025 N0, INC.

This project is licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

This project follows the iroh contributing guidelines. Please read them, along with our AI Policy, before opening an issue or pull request.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.