Packaging Luarocks

[gwerbin]

I am looking into packaging Luaposix and the Lua bindings for Readline. These are Lua packages that are typically distributed and installed using Luarocks.

I want to package these because Readline is an optional dependency of Fennel.

I wasn't able to find a single example of a Lua/Luarocks library in the Homebrew Core repo! I see some instances of Lua dependencies being downloaded as "resources", but not packaged as standalone Formulas.

What is the recommended procedure for packaging Luarocks packages?

I got as far as this:

  def install
    lua = Formula["lua"]
    system "luarocks", "--lua-dir=#{lua.prefix}", \
      "make", "--deps-mode" "none", "--no-install", \
      "luaposix-35.1-1.rockspec"
  end

This successfully builds the C extensions in-place and saves them to buildpath/"macos", but I'm not sure what to do next.

[SMillerDev]

Well, where do you want to install it?

[gwerbin]

Lua source files can go in /usr/local/share/lua/5.4/ or /usr/local/lib/lua/5.4/. Shared libraries can go in /usr/local/lib/lua/5.4/.

I didn't think it was possible to do something like Formula["lua"].lib.install, is it?

I noticed Pathname#env_script_all_files which seems to bundle up a bunch of dependencies in a single script, but that isn't useful here, either, because we want to put our library in a central location where other things can see it.

Maybe the correct solution is to add Readline to the Fennel formula itself somehow? Currently Fennel is built and installed as an "all-in-one" single Lua file with no external dependencies, but that's a special situation and can't be extended to include arbitrary 3rd-party dependencies (unless you do something really ridiculous like embed a bunch of compiled shared objects directly in the Lua script).

[carlocab]

I think we used to package Lua rocks, and then decided to stop and just vendor them into the formulae that need them. I haven't really been able to dig into the reasons why, but @DomT4 might remember if they have time to chime in.

Assuming the reasons for not packaging Lua rocks no longer apply: why not just install it into its own prefix? It'll get symlinked into $HOMEBREW_PREFIX/{share, lib}/lua/x.y that way making them globally accessible. The downside of this is that this install will interfere with a user's own installation if they'd ever done luarocks install on their own previously.

Also, why can't you just vendor Fennel's dependencies into its own prefix just like with other formulae that need Lua rocks?

[gwerbin]

It'll get symlinked into $HOMEBREW_PREFIX/{share, lib}/lua/x.y that way making them globally accessible. The downside of this is that this install will interfere with a user's own installation if they'd ever done luarocks install on their own previously.

Ah, that makes sense! It would be something like this?

/usr/local/Cellar/lua-readline/3.0.0/lib/lua/5.4/readline.lua
-> /usr/local/opt/lua-readline/lib/lua/5.4/readline.lua
-> /usr/local/lib/readline.lua

Isn't that how Python package used to be packaged? I think it's also how other package managers like APT, Pacman, DNF, Zypper, etc. do things. So I don't have a problem with it; that's kind of the point of installing a library anyway, right?

How would I do this in Homebrew language? lib.install_symlink and Dir somehow?

Also, why can't you just vendor Fennel's dependencies into its own prefix just like with other formulae that need Lua rocks?

Fennel appears to be packaged as a single standalone Lua script. I will try to vendor in the deps by installing Readline as a resource, and then wrapping fennel with env_script_all_files, order to set LUA_PATH accordingly.