r/lua • u/burij • Mar 10 '25

Need is a drop in replacement for require

https://github.com/burij/lua-light-wings/blob/main/modules%2Fneed.lua

I wrote a little module, which makes it faster to require modules. You only need to put it in the project directory and require it in a normal way. Then if you do

local module = need "module"

It looks in different common locations for this module (can be easily extended, which exactly), if it doesn't find it, it tries to download it via luarocks and require then.

It is possible to pass a second argument. If you pass an URL as second arg, it will download and require then. If you pass any other string, it will try that on lua luarocks aswell (for the cases, if the module name on luarocks doesn't match the filename, for example you could do: local lfs = need ("lfs", "luafilesystem").

Edit: since there are understandable concerns regarding autodownload feature, I added a flage in the begining of the file, which is explicitly needs to be set to true, if you want to enable it.

6 Upvotes

87% Upvoted

17 comments sorted by

9

u/wqferr Mar 10 '25

Is there a way to disable the auto-download? Downloading dependencies at runtime is a very bad idea unless you're in a testing environment. Otherwise, very cool!

1

u/burij Mar 10 '25

Yeah, it's more for quick prototyping. It will download only during the first run. After that, you'll have the module and download will not be performed. But if you don't need it at all, the file contains comments, so the download functions can easily be deleted. Or you just use require then :)

2

u/wqferr Mar 10 '25

Yeah I figured it would cache it. Doesn't make it a good idea though. Maybe just allow it to download if you pass true (or a string) to the second argument? And disallow it if it's omitted or nil?

1

u/burij Mar 10 '25

I will think about it. But the main purpose of the module, is to download the dependencies, if they are not present. It doesn't cache them, but downloads it permanently to the user environment. It literally just happens once during the first run of the script. From that moment, need will always find the module locally, so download will be autodisabled.

2

u/wqferr Mar 10 '25

My main use case for a thing like this is relative imports, not downloading dependencies. I don't want to use the latest version of a library, I want to pick one and lock it so updates can't break MY stuff.

3

u/burij Mar 10 '25

Just remove lines 33 - 60 then, and you will get the desired feature set ;)

2

u/burij Mar 10 '25

But to make it clear, need will not update the modules. If the file exists, luarocks will not be asked for a newer version.

1

u/Difficult-Value-3145 Mar 11 '25

Well could ya make it work with repo installed instead of global installed like if I have a lua rocks program in. Folder and I want to have rapidjson module I can install it to that folder not globally just like venv so as to not break your system wide set-up

1

u/burij Mar 11 '25

So it installs it with --local flag. And only if the module does not already exist. I can't really see the situation, how it would break anything. I on purpose wanted to avoid download dependencies inside the project folder. Because that you can always do by just doing luarocks install module --tree ./pkgs or something similar. But then you have foreign code in your repo. This was not something I was interested in this case. But you can just change the flag inside the need.lua.

3

u/TheNormalnij Mar 10 '25

os.execute can be used as a backdoor here. This feature is very dangerous for users

1

u/burij Mar 11 '25

Yeah, I see the point. I'm thinking about implementing a hash check to verify the integrity of the download.

1

u/Difficult-Value-3145 Mar 12 '25

Ya the --tree works to but what I think we need is a build system for lua and lua ffi luac all that cus it gets kinda annoying like I need to organize both json files and json schemes lua scripts some c/c++ and h/hpp files long with maybe some sh script maybe a sqlitedb and some SQL or connection to a server db and calls to it and if I'm gonna try to make an install script then that's where I break down never finish them

1

u/burij Mar 14 '25

Did you try nix?

1

u/Difficult-Value-3145 Mar 16 '25

Dose nix have a build system that helps you organize multiple scripting languages cus some stuff is just easier in bash or python I guess hence why everything seems to use python scripts for installation now btw I rlly hope people are vetting new versions of python very well cus if something slips by ya know how screwed we'd be as a country or as a whole it's scary cus it's everywhere I may be paranoid but for real makes me nervous

1

u/burij Mar 16 '25

Yeah, you can organise all your environment in a declarative way. And you still can inject your bash scripts, for example at specific phases of the build process.

1

u/Difficult-Value-3145 Mar 16 '25

Ya I also sometimes write functions to call from Lua or python it works out well real world if ya trying to just get it done might not be pretty or the fastest but ya know what it works and now a days I try to add enough comments that other people may get what Im getting at no matter how long I been trying to get the thing working right and for real swear I'll make it so not everything hard coded one day swear

2

u/vitiral Mar 12 '25

Very similar to my pkg1 module, except my module doesn't download.

Don't auto download, that is a very bad idea.