module Sprockets::Transformers

def compute_transformers!(registered_transformers)
  preprocessors         = self.config[:preprocessors]
  postprocessors        = self.config[:postprocessors]
  transformers          = Hash.new { {} }
  inverted_transformers = Hash.new { Set.new }
  incoming_edges        = registered_transformers.group_by(&:from)
  registered_transformers.each do |t|
    traversals = dfs_paths([t]) { |k| incoming_edges.fetch(k.to, []) }
    traversals.each do |nodes|
      src, dst = nodes.first.from, nodes.last.to
      processor = compose_transformer_list nodes, preprocessors, postprocessors
      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
  end
  self.config = hash_reassoc(config, :transformers) { transformers }
  self.config = hash_reassoc(config, :inverted_transformers) { inverted_transformers }
end