   By default it includes the mix.exs file, the lock manifest and
   all config files in the `config` directory.
   """
+  @spec config_files() :: [Path.t]
   def config_files do
     [Mix.Dep.Lock.manifest] ++
       case Mix.ProjectStack.peek do

  @doc """
  Returns all load paths for this project.
  """
  def load_paths(config \\ config()) do
    if umbrella?(config) do
      []

  is in build embedded mode, which may fail as a
  explicit command to `mix compile` is required.
  """
  @spec compile([term], Keyword.t) :: term
  def compile(args, config \\ config()) do
    if config[:build_embedded] do
      path = if umbrella?(config), do: build_path(config), else: compile_path(config)
