module Sprockets::Transformers

def compute_transformers!
  registered_transformers = self.config[:registered_transformers]
  transformers = Hash.new { {} }
  inverted_transformers = Hash.new { Set.new }
  registered_transformers.keys.flat_map do |key|
    dfs_paths([key]) { |k| registered_transformers[k].keys }
  end.each do |types|
    src, dst = types.first, types.last
    processor = compose_transformers(registered_transformers, types)
    transformers[src] = {} unless transformers.key?(src)
    transformers[src][dst] = processor
    inverted_transformers[dst] = Set.new unless inverted_transformers.key?(dst)
    inverted_transformers[dst] << src
  end
  self.config = hash_reassoc(config, :transformers) { transformers }
  self.config = hash_reassoc(config, :inverted_transformers) { inverted_transformers }
end