nix-gemspec

default.nix

{ stdenv, lib, makeWrapper, bundler, bundix, ruby }:

stdenv.mkDerivation {
  name = "nix-gemspec";
  src = ./.;
  buildInputs = [ makeWrapper ruby ];

  installPhase = ''
    install -D -m755 nix-gemspec.rb $out/bin/nix-gemspec
    patchShebangs $out/bin/nix-gemspec
    wrapProgram $out/bin/nix-gemspec \
        --prefix PATH : ${lib.makeBinPath [ bundler bundix ]}
  '';
}

nix-gemspec.rb

#!/usr/bin/env ruby

require "shellwords"

def sh(*args)
  $stderr.puts args.shelljoin
  system *args or fail "exit #{$?}"
end

sh "bundle", "lock"

require "fileutils"
p $:
require "bundler"

lockfile = Bundler::LockfileParser.new(File.read("Gemfile.lock"))
gems = lockfile.specs.select { |spec|
  case spec.source
  when Bundler::Source::Rubygems, Bundler::Source::Git then true
  end
}

FileUtils.mkdir_p "nix/gem"
Dir.chdir "nix/gem" do
  File.open("Gemfile", "w") do |gemfile|
    gems.group_by(&:name).each do |name, gems|
      gem = gems.sort_by { |gem| gem.platform.to_s }.first
      version = gem.version.to_s
      platform = Bundler::Dependency::REVERSE_PLATFORM_MAP[gem.platform]&.fetch(0)

      options = gem.source.options.transform_keys(&:to_sym)
      if uri = options.delete(:uri) then options[:git] = uri end
      if revision = options.delete(:revision) then options[:ref] = revision end
      if remote = options.delete(:remotes)&.first then options[:source] = remote end
      options[:platform] = platform if platform

      puts "gem #{name.inspect}, #{version.inspect}, #{options}"
      gemfile.puts "gem #{name.inspect}, #{version.inspect}, #{options}"
    end
  end

  sh "bundle", "lock", "--update"
  sh "bundix"
end