luau VS Prosody IM

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

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

On a side note, I've heard that they recently switched from Lua to Roblox's own fork of Lua, Luau.

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

https://luau-lang.org/ - some documentation, and examples https://create.roblox.com/docs - documentation, tutorials, and examples https://www.youtube.com/user/AlvinBLOX - tutorials https://www.youtube.com/@TheDevKing/videos - tutorials https://www.lua.org/manual/5.1/ - not specific to Roblox, but Lua reference manual https://www.codecademy.com/learn/learn-lua - Lua on Codecademy

XMPP server using Prosody

lua on its own right can be fun too! If you are looking for a project to contribute to, there's for instance the Prosody XMPP server that's written in it, and contributes to the betterment of internet by promoting federated protocols.

There's also the http://prosody.im/ XMPP server that's written in Lua, and it's very successful there. The other major XMPP server implementation is in Erlang and they are equally praised, so that should tell something about Lua's versatility.

Take your pick. Or just look here.

You can write largish standalone application in Lua and it is not always a poor choice - Prosody [1] first comes to mind. But qualities which make it a good embedded language make it less _attractive_ for other uses.

Lua has very simple syntax and small stdlib which allows its implementation to be very small - you can add Lua to your application and not increase its size significantly. But when the size is not a concern most programmers prefer languages with rich, powerful syntax lots of features and batteries-included stdlib (which is completely opposite of Lua).

[1] https://prosody.im/

If you are really set on a LAN-only setup you could look at Prosody (combined with an Android app such as Conversations) which Snikket is based upon. It's not as "ready to go, out of the box" as Snikket and therefore requires a slightly higher skill level, but in exchange it is a lot more customizable and adaptable to different kinds of deployment scenarios.

Selfhosting XMPP is pretty simple with https://prosody.im/

My choice, because it's the stack I know very well, would be Prosody ( https://prosody.im/ - I'm one of the devs) and a web client such as Converse.js ( https://conversejs.org/ ). XMPP is highly extensible, Prosody is highly modular, which make them a good foundation for building on top of.

That said, the right stack is generally the one that matches your requirements, and (if this isn't primarily a learning exercise) whatever you're most familiar with. The hardest part of building a Discord or Slack-like in 2022 is actually not the technical stuff. There are many comprehensive open-source products already out there that compete with these companies, such as Mattermost, RocketChat and Element.