Added File.listdir! variation

Author: n1rvana

lib/elixir/lib/file.ex

@@ -921,6 +921,21 @@ defmodule File do
     end
   end
 
+
+  @doc """
+  Get list of files in directories in `dir`.
+ 
+  Raises File.Error in case of an error.
+  """
+  def listdir!(dir) do
+    case F.list_dir(dir) do
+      { :ok, file_list } -> { :ok, Enum.map file_list, :unicode.characters_to_binary(&1) }
+      { :error, reason } ->
+        raise File.Error, reason: reason, action: "list directory", path: :unicode.characters_to_binary(dir)
+    end
+  end
+  
+
   @doc """
   Closes the file referenced by `io_device`. It mostly returns `:ok`, except
   for some severe errors such as out of memory.