webpacker_clean.rake

# frozen_string_literal: true

if Rake::Task.task_defined?('webpacker:clean')
  puts %(Task webpacker:clean has already been defined. The monkey patch located in "#{__FILE__}" can be removed.)
else
  module WebPackerClean
    def clean
      return if !config.public_output_path.exist? || !config.public_manifest_path.exist?

      count_to_keep = 2
      files_in_manifest = manifest.refresh.values.map { |f| File.join config.root_path, 'public', f }
      files_to_be_removed = files_in_manifest.flat_map do |file_in_manifest|
        file_prefix, file_ext = file_in_manifest.scan(/(.*)[0-9a-f]{20}(.*)/).first
        versions_of_file = Dir.glob("#{file_prefix}*#{file_ext}").grep(/#{file_prefix}[0-9a-f]{20}#{file_ext}/)
        versions_of_file.map do |version_of_file|
          next if version_of_file == file_in_manifest

          [version_of_file, File.mtime(version_of_file).utc.to_i]
        end.compact.sort_by(&:last).reverse.drop(count_to_keep)].map(&:first)
      end

      files_to_be_removed.each { |f| File.delete f }
    end
  end

  Webpacker::Commands.class_eval { include WebPackerClean }

  module Webpacker
    class Commands
      include WebPackerClean
    end
  end

  namespace :webpacker do
    desc 'Remove old compiled webpacks'
    task clean: ['webpacker:verify_install', :environment] do
      Webpacker.commands.clean
    end
  end

  # Run clean if the assets:clean is run
  if Rake::Task.task_defined?('assets:clean')
    Rake::Task['assets:clean'].enhance do
      Rake::Task['webpacker:clean'].invoke
    end
  end
end

I placed this file in lib/tasks/webpacker_clean.rake in my Rails project to backport rails/webpacker#1744.