PuercoPop / vendoring-ruby-gems-in-nix

How to vendor ruby gems using Nix?

First approach: Try to call bundler cache from inside a bundlerEnv

This fails because bundle cache tries to set the CACHE_ALL_PLATFORMS option before running the command. This tries to write the config next to the Gemfile, which is in the nix store. So it fails.

$ nix -A defeault
$ bundle cache
There was an error while trying to write to `/nix/store/3b0fsiq7fcfx3aakmhj1xbigpbq4m3km-gemfile-and-lockfile/.bundle/config`. It is likely that you need
to grant write permissions for that path.

Second approach: Using bundix's -m flag

Bundix has an option named magic which seems to call bundle pack, which is an alias for cache. It takes a ruby argument which is an expression to fill the whole in to bundler.override { _ruby = ?_? }.

$ nix-shell -A update
$ bundix -m                      # Your Ruby version is 2.7.6, but your Gemfile specified 3.2
$ bundix -m --ruby=ruby          # Your Ruby version is 2.7.6, but your Gemfile specified 3.2
$ bundix -m --ruby=pkgs.ruby_3_2 # Success! 🙌