lua5_1, luajit and original luajit behave differently

[junchih]

Describe the bug

-- "tasting.lua"
print(string.gsub(package.path, ";", "\n").."\n")

Will behave differently on host luajit, nixpkg luajit and nixpkg lua5_1.

Expected behavior

1. From LUA_PATH_DEFAULT of luaconf.h, there is not way lua runtime will automatically defaultly load something like ./myPkg/init.lua, but lua5_1 of nixpkg 22.05 will do this. I'm new to nix, can't see why?
2. luajit and lua5_1 of nixpkg 22.05 behave differently. luajit will load all lua module from system path, lua5_1 will load all package from working directory. And both differently with my host luajit, which load module from both working directory and system path.
3. Anyway, seems same patch both in lua5_1 and luajit, https://github.com/NixOS/nixpkgs/blob/22.05/pkgs/development/interpreters/luajit/default.nix#L62-L69, but luajit doesn't work expectly, so the default luajit from nixpkg 22.05 can't do anything as a standalone lua interpreter.

Screenshots

On macOS 12.5.1, LuaJIT 2.1.0-beta3

./?.lua
/usr/local/share/luajit-2.1.0-beta3/?.lua
/usr/local/share/lua/5.1/?.lua
/usr/local/share/lua/5.1/?/init.lua
/usr/local/share/lua/5.1/?.lua
/usr/local/share/lua/5.1/?/init.lua

On luajit of nixpkgs 22.05 with helping of shell.nix

/nix/store/db6sp8wgr97zn4qyyb7g42yhr00pqjiy-luajit-2.1.0-2022-04-05/share/lua/5.1/?.lua
/nix/store/db6sp8wgr97zn4qyyb7g42yhr00pqjiy-luajit-2.1.0-2022-04-05/share/lua/5.1/?/init.lua

On lua5_1 of nixpkgs 22.05 with helping of shell.nix

./share/lua/5.1/?.lua
./?.lua
./?/init.lua

Notify maintainers

@teto, 8884291

Metadata

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
blabla...
blabla...
...
 - system: `"x86_64-darwin"`
 - host os: `Darwin 21.6.0, macOS 10.16`
 - multi-user?: `no`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.3.15`
 - channels(jack): `"nixpkgs-21.11pre306870.67c80531be6"`
 - nixpkgs: `/Users/jack/.nix-defexpr/channels/nixpkgs`

[teto]

The lua ecosystem needs some love see:

• lua: test the interpreter #177556
• harmonize lua wrapping across nixpkgs #169229
• Meta issue about lua ecosystem progress #56398

The incentive for patching the interpreter is to increase purity and avoid loading inadvertendly stuff from /usr/local/share/. We could always wrap but someone using ";;" (i.e. "add default") in its LUA_PATH could inadvertendly break stuff.
What could be interesting is to add your test cases to #177556 .

you can use lua.withPackages(p: [ p.cqueues ]); to create a lua with the packages you need.

[junchih]

Sorry, don't have much free time to read all the resources.

Let's see how the issue infects daily development work.

• issue 1, after I've done a few relating lua script development. There is some code such as require "mypkg", and the expecting loading file is mypkg/init.lua. Testing with nix-shell + lua5_1 will pass, but still could not be interpreted by downloaded original lua 5.1 without any additional configuration.
• issue 3, obviously, if I just get luajit with nix-shell, and do nothing about configuration. The command luajit ./main.lua will surely failed. But weird, the ./main.lua was just tested by me with the luajit of the OS hosted one. With both same luajit version number, and both same zero configuration.

And of course, with correcting LUA_PATH env, this issue could be nonsense. But I don't think some logically unnecessary configurations is good idea for libraries to be portable and maintaining.

[teto]

bottomline was: you are right, things are broken and this is bad. Patches/tests welcomes

[teto]

should be fixed by #286822

[teto]

should be fixed on master see those tests

nixpkgs/pkgs/development/interpreters/lua-5/tests/default.nix

Line 42 in 6c0dc57

"5.4" = "${lua}/share/lua/5.4/?.lua;${lua}/share/lua/5.4/?/init.lua;${lua}/lib/lua/5.4/?.lua;${lua}/lib/lua/5.4/?/init.lua;./?.lua;./?/init.lua";

. I'll let you close once you are confident that fixed the issue