Jarred tried rewriting Bun in Rust and it passes 99.8% of the existing test suite we’re not being ambitious enough

Jarred has successfully rewritten Bun, a JavaScript runtime, in Rust, with the new implementation passing 99.8% of its existing test suite, according to a recent tweet. This milestone suggests promising advancements in performance and reliability, attracting attention from developers and the tech community.

The effort, led by Jarred, involved creating a Rust-based version of Bun, which is known for its speed and modern architecture. The rewritten version has completed 99.8% of the test suite designed to validate its functionality and stability. The remaining 0.2% of tests are yet to be passed, but the progress indicates that the core features are largely functional.

Jarred’s announcement on X (formerly Twitter) emphasized that this is a significant step forward, stating, “we’re not being ambitious enough” in terms of progress. The project aims to leverage Rust’s safety and performance benefits to improve Bun’s overall capabilities, especially in areas like concurrency and memory safety.

Why It Matters

This development is notable because Bun is a popular JavaScript runtime that aims to compete with Node.js and Deno by offering faster startup times and lower latency. A Rust-based version could potentially enhance these aspects further, making it attractive for high-performance applications. Additionally, passing such a high percentage of tests suggests the implementation is approaching production readiness, which could influence future JavaScript runtime designs.

Background

Bun was originally developed in JavaScript and C++, emphasizing speed and modern features. Its community has been actively exploring alternative implementations to improve performance and security. Jarred’s initiative to rewrite Bun in Rust is part of broader efforts within the developer community to experiment with language choices that enhance safety and efficiency. Prior to this, Bun’s development focused on incremental improvements; this rewrite represents a more ambitious attempt at re-engineering the platform entirely.

“We’re not being ambitious enough.”

— Jarred

“Passing 99.8% of the test suite is a major milestone, but there’s still work to do before it can be considered production-ready.”

— Unspecified developer involved in the project

What Remains Unclear

It is not yet clear when the Rust implementation of Bun will be fully complete or stable enough for production use. The remaining 0.2% of tests could reveal critical issues, and performance benchmarks compared to the original are still pending. Additionally, community adoption and integration details remain to be seen.

What’s Next

Next steps include addressing the remaining test failures, conducting performance benchmarking, and possibly releasing alpha or beta versions for community testing. Developers involved will likely focus on stabilizing the implementation and documenting the migration process for potential users.

Key Questions

What is Bun, and why is rewriting it in Rust significant?

Bun is a JavaScript runtime designed for speed and modern development. Rewriting it in Rust is significant because Rust offers safety and performance advantages, which could improve Bun’s efficiency and security.

How close is the Rust version of Bun to being production-ready?

While passing 99.8% of tests is promising, it is not yet clear when the implementation will be stable enough for production use. Further testing and development are ongoing.

What are the main benefits of using Rust for Bun?

Rust provides memory safety, concurrency support, and performance benefits, which could make Bun faster, more reliable, and easier to maintain.

Will this rewrite replace the existing Bun in JavaScript?

It is too early to say whether the Rust version will replace the existing Bun. The project is still in development, and community adoption will influence its future role.