Rust @programming.dev asudox @programming.dev 3d ago

Embedded and sandboxed scripting languages in Rust

I want to allow the users of my project be able to write the driving logic, while I provide the tools. What are some embedded scripting languages in Rust that can be sandboxed and are easy for absolute beginners?

edit: Thanks for all of your answers, I decided to go with lua using mlua

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Another meme answer: nu.

I never actually used nu for anything. But I've been thinking (unironically) that nu with its built-in from_json and to_json can be interesting.

The use-case I had in mind is not games or anything like that, but some system or dev tools that traditionally utilized shell scripts, but are moving towards better languages like python. So I thought a single binary that embeds nu, but also has a lot of sub-commands that implement a lot of sub-tasks in Rust directly, and with JSON used as an exchange format, the combination can be interesting.

Now that I think about it more, this can work in both directions, with main execution being in nu (what I had in mind), or in Rust.

nu even has an lsp server, so the development experience should theoretically be good.
- As a sysadmin Python is very far from a better language than Shell, it is much too fragile over time for that. You can't even rely on a Python script running unmodified on the oldest currently supported OS versions and the latest ones.
Would something like Steel work?

The Helix editor is working on adding it as a plugin scripting language. You could take a look at the in-progress fork to see how they're doing it.
- PreFix notation for mathematical operations. Hehe.
  Interesting for me, but I'd rather not give this to someone who us more interested in making a plugin and calling it a day.
Many languages can be compiled to wasm, and it's quite easy to load and run wasm from rust

That way you could give the user multiple options, they could write it in rust, c, c++, javascript, etc
- Although the OP has already decided to go with Lua, if anyone else looking at this thread is considering their options for making a plugin system, WASM/WASI is an excellent choice - mostly because it allows users to use Python (a favorite among programming newbies) along with any other language that compiles to WebAssembly (which will eventually be all languages).
  
  You can even use something like Extism which is purpose-built as a drop-in library for creating a plugin system with WASM plugins, or you can use other runtime options like Wasmtime (built in Rust, from the ByteCode Alliance - where the WASI spec is being developed) or the WasmEdge runtime (built in C++, which is a CNCF project and is already being used in areas like eBPF to help users build Linux Kernel extensions).
  
  In short, if you're building a project that has to be maintained long-term and you need a plugin system, then choose WebAssembly - you can't go wrong.
  
  Cheers!
- WASM is a bit overkill and is also complicated. I need a simple scripting language that won't stress the users out. As mentioned in my post, I expect them to be absolute beginners.
  
  I didn't mean that the users would write wasm, just that they could write it in some language, then your program would compile it to wasm and run it
  
  Gives some flexibility as to the choice of language and it runs sandboxed
Crates.io has tags like scripting. It suggests languages like rhai, dyon, or rune.
There is a Python interpreter written in Rust. It's apparently intended to (besides being fast an all that) make Rust scriptable.
- I'm aware that pyo3 is a thing, but last I checked that was just Rust bindings to CPython. Is this not that?
  
  https://github.com/RustPython/RustPython
The most battletested way is via bindings to other languages. Ex. mlua with luau sandboxing Or Javascript via v8 or deno_core

There are also a few languages implemented in rust like rhai

There is also the option of compiling the user code to wasm and using wasmtime to run it
- Seems like Luau will do. Thanks
There's a list of good options on Are We Game Yet, hope one of these crates is useful. https://arewegameyet.rs/ecosystem/scripting/
Boa is a remarkably well-developed JS runtime written in Rust. Nice API, and well sandboxed. We’re considering adopting it for Biome as well.
- Thanks for the suggestion. Though JS itself is a pretty weird language and has some weird behaviours, I'd rather not use it. It's also a bit too advanced for my use case. (somewhat simple control flow, maybe some math, etc.)
One more vote for using WASM. Using WASM has the benefit of allowing the user to use almost whatever language they want, as long as it can compile to WASM. So the user doesn't have to learn some bespoke scripting-specific language.

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