sprockets-loader pre-script

sprockets-loader-pre-script.rb

# Script to go through all files in a specified directory (defaults to javascirpts)
# and replace all relative `require`, `require_tree` and `require_directory` paths
# as absolute paths given `app/assets/javascripts` as root
#
# This is useful for using sprockets-loader (or webpack loaders in general because there is no access
# to path related information)

require 'Pathname'

JAVASCRIPT_ROOT = Pathname.new('app/assets/javascripts/')

def add_extension(require_file)
  ['', '.js', '.js.coffee', '.coffee', '/index.js', '/index.coffee'].each do |extension|
    file = "#{require_file}#{extension}"
    file_with_extension = Pathname.new("#{JAVASCRIPT_ROOT.to_s}/#{file}")
    return file if !file_with_extension.directory? && file_with_extension.exist?
  end

  puts 'WARNING: Cannot find file (js / coffee / index) -- maybe a gem / vendor file:'
  puts "Preserving require directive: #{require_file}", ''
  require_file
end

file_names = Dir.glob('app/assets/javascripts/**/*.js')
# file_names = Dir.glob('app/assets/javascripts/**/*.coffee')

file_names.each do |file_name|
  dirname = Pathname.new(file_name).dirname
  source = File.read(file_name)
  lines = source.split("\n") # .each_line / .lines always has trailing newline

  new_source = lines.reduce('') do |new_source, line|
    new_line = if matches = /(\/\/=)\s*(require)\s+(\S+)/.match(line)
    # new_line = if matches = /(#=)\s*(require)\s+(\S+)/.match(line)
      new_require_path = if matches[3][0] == '.'
        Pathname.new("#{dirname.to_s}/#{matches[3]}").relative_path_from(JAVASCRIPT_ROOT)
      else
        matches[3]
      end

      # puts 'require match!', file_name, line, new_require_path, ''
      # "#{matches[1]} #{matches[2]} #{matches[3]}" # whitespace fixes only
      "#{matches[1]} #{matches[2]} #{add_extension(new_require_path)}"

    elsif matches = /(\/\/=)\s*(require_tree)\s+(\S+)/.match(line)
    # elsif matches = /(#=)\s*(require_tree)\s+(\S+)/.match(line)
      new_require_path = if matches[3][0] == '.'
        Pathname.new("#{dirname.to_s}/#{matches[3]}").relative_path_from(JAVASCRIPT_ROOT)
      else
        matches[3]
      end

      unless Pathname.new("#{JAVASCRIPT_ROOT}/#{new_require_path.to_s}").directory?
        puts 'WARNING: Cannot find directory!:'
        puts "Preserving require_tree directive: #{new_require_path}", ''
      end

      # puts 'require match!', file_name, line, new_require_path, ''
      "#{matches[1]} #{matches[2]} #{new_require_path}"

    elsif matches = /(\/\/=)\s*(require_directory)\s+(\S+)/.match(line)
    # elsif matches = /(#=)\s*(require_directory)\s+(\S+)/.match(line)
      new_require_path = if matches[3][0] == '.'
        Pathname.new("#{dirname.to_s}/#{matches[3]}").relative_path_from(JAVASCRIPT_ROOT)
      else
        matches[3]
      end

      unless Pathname.new("#{JAVASCRIPT_ROOT}/#{new_require_path.to_s}").directory?
        puts 'WARNING: Cannot find directory!:'
        puts "Preserving require_directory directive: #{new_require_path}", ''
      end

      # puts 'require match!', file_name, line, new_require_path, ''
      "#{matches[1]} #{matches[2]} #{new_require_path}"

    else
      line
    end

    new_source += new_line + "\n"
  end

  # puts new_source
  File.open(file_name, "w") {|file| file.puts new_source }
end