How do I set up a nix-shell script for lua?

Question

I am trying to set up a nix-shell script which contains lua 5.2, the lua sockets library, and a few other libraries. However, when I load the shell, only Lua ends up being present.

with import <nixpkgs> {}; stdenv.mkDerivation rec { name = "lua-env"; buildInputs = [ lua52Packages.lua lua52Packages.luasocket lua52Packages.luasec lua52Packages.cjson ]; } 

When I run the shell, this is what I get:

savanni@lapis:~ $ nix-shell lua.nix [nix-shell:~]$ lua Lua 5.2.3 Copyright (C) 1994-2013 Lua.org, PUC-Rio > require 'socket' stdin:1: module 'socket' not found: no field package.preload['socket'] no file '/usr/share/lua/5.2/socket.lua' no file '/usr/share/lua/5.2/socket/init.lua' no file '/usr/lib/lua/5.2/socket.lua' no file '/usr/lib/lua/5.2/socket/init.lua' no file './socket.lua' no file '/usr/lib/lua/5.2/socket.so' no file '/usr/lib/lua/5.2/loadall.so' no file './socket.so' stack traceback: [C]: in function 'require' stdin:1: in main chunk [C]: in ? > [nix-shell:~]$ exit savanni@lapis:~ $ 

Answer 1

You have to set LUA_PATH and LUA_CPATH

This shell.nix should work,

with import <nixpkgs> {}; with luaPackages; let libs = [lua cjson luasocket luasec]; in stdenv.mkDerivation rec { name = "lua-env"; buildInputs = libs; shellHook = '' export LUA_CPATH="${lib.concatStringsSep ";" (map getLuaCPath libs)}" export LUA_PATH="${lib.concatStringsSep ";" (map getLuaPath libs)}" ''; } 

To check that those paths are exported,

$ nix-shell --run 'echo $LUA_CPATH; echo $LUA_PATH' /nix/store/lp0ns0hjwx1klk6amnyic3f62bw7h8j7-lua-5.2.3/lib/lua/5.2/?.so;/nix/store/lp0ns0hjwx1klk6amnyic3f62bw7h8j7-lua-5.2.3/share/lua/5.2/?.so;/nix/store/ppdspfcm5nnfz0fk9zarjmpyv5lcmn18-lua5.2-cjson-2.1.0/lib/lua/5.2/?.so;/nix/store/ppdspfcm5nnfz0fk9zarjmpyv5lcmn18-lua5.2-cjson-2.1.0/share/lua/5.2/?.so;/nix/store/b71xyq7gkc8iccj6wr84zq31gqc3m9ix-lua5.2-socket-3.0-rc1/lib/lua/5.2/?.so;/nix/store/b71xyq7gkc8iccj6wr84zq31gqc3m9ix-lua5.2-socket-3.0-rc1/share/lua/5.2/?.so;/nix/store/6q8xn2bcfskmrfzql47jld5d2irvn5jr-lua5.2-sec-0.6/lib/lua/5.2/?.so;/nix/store/6q8xn2bcfskmrfzql47jld5d2irvn5jr-lua5.2-sec-0.6/share/lua/5.2/?.so /nix/store/lp0ns0hjwx1klk6amnyic3f62bw7h8j7-lua-5.2.3/lib/lua/5.2/?.lua;/nix/store/lp0ns0hjwx1klk6amnyic3f62bw7h8j7-lua-5.2.3/share/lua/5.2/?.lua;/nix/store/ppdspfcm5nnfz0fk9zarjmpyv5lcmn18-lua5.2-cjson-2.1.0/lib/lua/5.2/?.lua;/nix/store/ppdspfcm5nnfz0fk9zarjmpyv5lcmn18-lua5.2-cjson-2.1.0/share/lua/5.2/?.lua;/nix/store/b71xyq7gkc8iccj6wr84zq31gqc3m9ix-lua5.2-socket-3.0-rc1/lib/lua/5.2/?.lua;/nix/store/b71xyq7gkc8iccj6wr84zq31gqc3m9ix-lua5.2-socket-3.0-rc1/share/lua/5.2/?.lua;/nix/store/6q8xn2bcfskmrfzql47jld5d2irvn5jr-lua5.2-sec-0.6/lib/lua/5.2/?.lua;/nix/store/6q8xn2bcfskmrfzql47jld5d2irvn5jr-lua5.2-sec-0.6/share/lua/5.2/?.lua 

Answer 2

There is a simpler way to do this in 2020:

nix-shell -p 'lua.withPackages(ps: [ps.luasocket ps.cjson])' 

This will put a modified lua derivation in your environment where the luasocket and cjson derivations from luaPackages are included in the LUA_PATH.

So you do not need to mess with LUA_PATH or shellHooks yourself.

EDIT:

You can use the lua.withPackages function in a nix file as well:

with import <nixpkgs> {}; stdenv.mkDerivation rec { name = "lua-env"; buildInputs = [ lua.withPackages(ps: with ps; [luasocket luasec cjson ]) ]; }