luau VS fengari

As far as I can tell, they aren't.

http://lua-users.org/wiki/SandBoxes

There is a lot of information there, but it doesn't handle resource exhaustion, execution time limits or give any guarantees. It does indicate that it's possible, and has a decent example of the most restrictive setup, which is a good start. But I would for example compare it with Luau's SECURITY.md.

From https://github.com/luau-lang/luau/blob/master/SECURITY.md:

> Luau provides a safe sandbox that scripts can not escape from, short of vulnerabilities in custom C functions exposed by the host. This includes the virtual machine and builtin libraries. Notably this currently does not include the work-in-progress native code generation facilities.

> Any source code can not result in memory safety errors or crashes during its compilation or execution. Violations of memory safety are considered vulnerabilities.

> Note that Luau does not provide termination guarantees - some code may exhaust CPU or RAM resources on the system during compilation or execution.

So, even luau will have trouble with untrusted code, but it specifies exactly what happens and so on. I think that's fair enough.

Alternatively, Luau is a well-supported Lua variant with type checking and performance improvements, aimed more towards being a sandboxed embedded scripting environment.

https://luau-lang.org/

If you need Lua but also type-safety, how about Luau [1] then?

[1] https://luau-lang.org/

I had the pleasure of working with Lua 5.1 back in the late noughties. For me it's replaced Tcl whenever I want something I can configure above a C library. At the time I used it I found it quite nice but I'll also not forget the hours I wasted tracking down nil table corruptions which could have easily been caught by a type checker.

I had some hope that Luau https://luau-lang.org or Teal https://github.com/teal-language/tl would make things better but with the following example

    function foo(x: number): string

I use Luau in my games and tools [1], and I recommend it. While I can't speak to transitioning to it from Lua, since I didn't do that, I can say that it's fast, stable, sandboxing just works (important for your use case), and it's very well supported and regularly updated.

For context, I first started using Luau as an experimental hack by integrating it with Unity. I mostly just wanted fast and simple hot reloading. I found myself writing more and more of it, and now I'm writing most of my code in it.

VS Code support is pretty good via the luau-lsp language server [2]. Type support for certain code patterns isn't great yet, but there are RFCs to improve this.

They're also quietly working on native code gen and JIT support, e.g. this PR from a few hours ago [3].

Overall, recommended! You're not crazy.

[1] https://twitter.com/kineticpoet

[2] https://github.com/JohnnyMorganz/luau-lsp

[3] https://github.com/Roblox/luau/pull/1076

Looking at other replies here, I can see I wasn't the only one who didn't realize there is Lua and Luau. Luau is an extension of Lua: https://luau-lang.org/

> Luau is syntactically backwards-compatible with Lua 5.1 (code that is valid Lua 5.1 is also valid Luau); however, we have extended the language with a set of syntactical features that make the language more familiar and ergonomic.

Lua is usually the embedded language of choice. If you are focused on security, you could check out the Roblox fork, Luau (https://github.com/Roblox/luau) where the creators took extra care to lock down the language on what scripts could do.

Luau - Lua variant by Roblox

https://www.youtube.com/results?search_query=luau+roblox&sp=...

Luau

https://github.com/Roblox/luau

Roblox wrote a superset of Roblox Lua which is way faster

it should be possible, the article mentions https://fengari.io/ (a Lua VM written in JavaScript)

Other languages have done that :)

Lua in the browser: https://fengari.io/

And then you can use that to run Fennel, a Lisp that compiles to Lua https://fennel-lang.org/

I think TypeScript also has a script you can include that lets you put your TS code in a special script tag, and it gets compiled in-browser.

Please stop this stuck in the mud nonsense. Anyone stumbling upon lua.org might think the project is dead already. The material is great, close to the best, but its presentation is pure shite. Not mobile friendly (what kinds of device do you think the majority of people in the Global South use?). We live in a world of code highlighting, none of that in PiL. We live in a world where Fengari allows Lua to run in the browser, does that make an appearance on lua.org, allowing users to immediately play with the language? Of course not! It's almost as if the Lua team is trying to push away potential users.

Fengari – Lua for the Browser\ (57 comments)

Lua 5.3’s not really a fork. It just has backwards-incompatible changes, as do 5.1, 5.2 and 5.4.

Otherwise yes, “Fengari implements Lua 5.3”. https://github.com/fengari-lua/fengari

Please note, my original comment was simply correcting the notion that JS is popular because it was especially well suited for working on the web. I see projects like Fengari[1] and would _love_ to use something like that but I recognize I can't impose an extra 300kb on end users just because I want to write in a more pleasant language to develop. I accept that JS is what we have, but I won't pretend like JS was the cream that rose to the top.

[1]: https://fengari.io/

WoW's UI API is written in Lua. If you aren't familiar, Lua is a great little scripting language built on top of C, designed to be embedded into larger pieces of software. You can even, thanks to web assembly, run it in the browser. It has some quirks that take some getting used to (Lua's Arrays start at index 1 👀), but by and large it's great at what it does and can be found everywhere in computer game UIs.

> I’d expect MicroPython (or Lua/mruby/etc) could be an order of magnitude smaller. Still larger (and slower) than just using JavaScript, though.

Fengari [0], a Lua interpreter written in JS, is a little over 200Kb. (And was intentionally written in JS [1] because of a variety of reasons that made WASM not work that well.

200Kb isn't that bad of a price to pay to switch languages, on most websites. It'll be about the cost of a single image added to the page. And it's fairly performant.

For most sites, the costs in terms of requests and performance will be negligible compared to what you're trying to achieve.

And Fengari makes it nice and easy to interact with JS, too. Using React with Lua's syntax was what sold me on it. No ecosystem lockout, like I'd expect with most WASM ports.

[0] https://fengari.io/

[1] https://hackernoon.com/why-we-rewrote-lua-in-js-a66529a8278d