Count lines of code per gem in your Gemfile

gem_loc.rb

# gem_loc.rb
#
# Output require-able lines of code gems in your Gemfile
#
# Usage: rails runner <path to this file>

require "rails/code_statistics_calculator"
require "csv"

gem_specs = Bundler::LockfileParser.new(Rails.root.join("Gemfile.lock").read).specs.each(&:__materialize__)
gem_file_paths = gem_specs.map do |gem_spec|
  file_paths = gem_spec.full_require_paths.flat_map do |require_path|
    Dir.glob("#{require_path}/**/*.rb").to_a
  end

  [gem_spec.name, file_paths]
end.to_h

stats_by_gem = Hash.new {|hash, key| hash[key] = CodeStatisticsCalculator.new }
gem_file_paths.each do |gem_name, file_paths|
    file_paths.each do |file_path|
      begin
        stats_by_gem[gem_name].add_by_file_path(file_path)
      rescue
        STDERR.puts("#{$!.class} raised. Skipping #{file_path}")
      end
    end
end

include ActionView::Helpers::NumberHelper

csv_string = CSV.generate do |csv|
  csv << ["Gem Name", "Lines of code"]

  stats_by_gem.sort_by {|gem_name, stats| stats.code_lines }.each do |gem_name, stats|
    csv << [gem_name, number_with_delimiter(stats.code_lines)]
  end

  rails_gems = ["actioncable", "actionmailbox", "actionmailer", "actionpack", "actiontext", "actionview", "activejob", "activemodel", "activerecord", "activestorage", "activesupport", "railties"]
  csv << ["rails/rails", stats_by_gem.sum {|gem_name, stats| rails_gems.include?(gem_name) ? stats.code_lines : 0 }]
  csv << ["Total", stats_by_gem.sum {|_gem_name, stats| stats.code_lines }]
end

puts csv_string