class Sprockets::Rails::Helpers::RailsHelper::AssetPaths

def digest_for(logical_path)
  if digest_assets && asset_digests && (digest = asset_digests[logical_path])
    return digest
  end
  if compile_assets
    if digest_assets && asset = asset_environment[logical_path]
      return asset.digest_path
    end
    return logical_path
  else
    raise AssetNotPrecompiledError.new("#{logical_path} isn't precompiled")
  end
end