[Media] I built “Decide” – a role and condition-based permission engine for Rust (and also JS/TS)

I recently released Decide, a fast and lightweight permission engine written in Rust, with built-in support for both Rust and JavaScript/TypeScript.

It started as a small idea, but turned into something I genuinely found useful, especially because there weren’t many simple permission engines for Rust.

⚙️ What Decide does

• Role + condition based permission engine
• Supports conditions like: user_id === resource_owner
• Built in Rust (uses Rhai for condition evaluation)
• Comes with a JS/TS wrapper (using napi-rs)
• Published on Crates.io and NPM

GitHub Repo

The code is completely open to view. Visit the repository here.

An example usage is given in the code snippet. The part Decide::default() gets the role definitions from a decide.config.json file.

Why I Made It

There are a bunch of libraries for auth or RBAC in JS, but almost none in Rust. I thought, why not build a clean one that works for both?

It’s fully open-source and MIT licensed.

Would love to hear your thoughts

It's my first time posting here, and I'd love feedback. Especially around:

• Rust conventions or improvements
• Performance ideas

Thanks for reading, I hope this can help someone actually :)