promisery

A JavaScript-inspired, ergonomic, and composable Promise type for Rust, supporting background work, chaining, and error handling with Result.

Features

• ECMAScript 5-style promises with Rust's type safety
• Chaining with .then, .map, and .map_err
• Combinators: Promise::all, Promise::race
• Panic-safe: panics in promise tasks are detected and reported (see Promise::wait_nopanic)
• Fully documented with tested examples

Installation

Add to your Cargo.toml:

promisery = "1.0.0"

Example

use promisery::Promise;

let p = Promise::<_, ()>::new(|| Ok(2))
    .then(|res| res.map(|v| v * 10))
    .then(|res| res.map(|v| v + 5));
assert_eq!(p.wait(), Ok(25));

API Highlights

• Chaining:
  • .then for full control over result and error
  • .map for value transformation
  • .map_err for error transformation
• Combinators:
  • Promise::all waits for all promises
  • Promise::race resolves/rejects with the first to finish
• Panic Handling:
  • Panics in promise tasks are detected and reported via PromisePanic
  • Use .wait_nopanic() to safely handle panics

Why promisery?

• Lightweight, no async runtime required
• Familiar API for those coming from JavaScript
• Integrates with Rust's Result-based error handling
• Does not spawn a new thread for each action that produces a new promise (see the documentation for each method for more details)

License

MIT OR Apache-2.0

See docs.rs/promisery for full documentation and more examples.