Add IO.stream/0 and IO.binstream/0 as convenience functions

Author: josevalim

lib/elixir/lib/io.ex

@@ -508,6 +508,16 @@ defmodule IO do
     :io.get_line(map_dev(device), to_chardata(prompt))
   end
 
+  @doc """
+  Returns a line-based `IO.Stream` on `:stdio`.
+
+  This is equivalent to:
+
+      IO.stream(:stdio, :line)
+
+  """
+  def stream, do: stream(:stdio, :line)
+
   @doc """
   Converts the IO `device` into an `IO.Stream`.
 
@@ -533,12 +543,22 @@ defmodule IO do
 
   """
   @spec stream(device, :line | pos_integer) :: Enumerable.t()
-  def stream(device, line_or_codepoints)
+  def stream(device \\ :stdio, line_or_codepoints)
       when line_or_codepoints == :line
       when is_integer(line_or_codepoints) and line_or_codepoints > 0 do
     IO.Stream.__build__(map_dev(device), false, line_or_codepoints)
   end
 
+  @doc """
+  Returns a raw, line-based `IO.Stream` on `:stdio`. The operation is Unicode unsafe.
+
+  This is equivalent to:
+
+      IO.binstream(:stdio, :line)
+
+  """
+  def binstream, do: binstream(:stdio, :line)
+
   @doc """
   Converts the IO `device` into an `IO.Stream`. The operation is Unicode unsafe.
 
@@ -547,18 +567,16 @@ defmodule IO do
   and write.
 
   The `device` is iterated by the given number of bytes or line by line if
-  `:line` is given.
-  This reads from the IO device as a raw binary.
+  `:line` is given. This reads from the IO device as a raw binary.
 
   Note that an IO stream has side effects and every time
   you go over the stream you may get different results.
 
   Finally, do not use this function on IO devices in Unicode
   mode as it will return the wrong result.
-
   """
   @spec binstream(device, :line | pos_integer) :: Enumerable.t()
-  def binstream(device, line_or_bytes)
+  def binstream(device \\ :stdio, line_or_bytes)
       when line_or_bytes == :line
       when is_integer(line_or_bytes) and line_or_bytes > 0 do
     IO.Stream.__build__(map_dev(device), true, line_or_bytes)

lib/elixir/lib/kernel/special_forms.ex

@@ -1416,7 +1416,7 @@ defmodule Kernel.SpecialForms do
   The `IO` module provides streams, that are both `Enumerable` and
   `Collectable`, here is an upcase echo server using comprehensions:
 
-      for line <- IO.stream(:stdio, :line), into: IO.stream(:stdio, :line) do
+      for line <- IO.stream(), into: IO.stream() do
         String.upcase(line)
       end
 

lib/elixir/lib/system.ex

@@ -897,6 +897,12 @@ defmodule System do
       iex> System.shell("echo hello")
       {"hello\n", 0}
 
+  If you want to stream the devices to IO as they come:
+
+      iex> System.shell("echo hello", into: IO.stream())
+      hello
+      {%IO.Stream{}, 0}
+
   ## Options
 
   It accepts the same options as `cmd/3`, except for `arg0`.
@@ -963,7 +969,9 @@ defmodule System do
       iex> System.cmd("echo", ["hello"], env: [{"MIX_ENV", "test"}])
       {"hello\n", 0}
 
-      iex> System.cmd("echo", ["hello"], into: IO.stream(:stdio, :line))
+  If you want to stream the devices to IO as they come:
+
+      iex> System.cmd("echo", ["hello"], into: IO.stream())
       hello
       {%IO.Stream{}, 0}
 

lib/elixir/test/elixir/io_test.exs

@@ -210,4 +210,9 @@ defmodule IOTest do
     assert capture_io(fn -> IO.inspect(1, label: "foo") end) == "foo: 1\n"
     assert capture_io(fn -> IO.inspect(1, label: :foo) end) == "foo: 1\n"
   end
+
+  test "stream" do
+    assert IO.stream() == IO.stream(:stdio, :line)
+    assert IO.binstream() == IO.binstream(:stdio, :line)
+  end
 end

lib/mix/lib/mix/scm/git.ex

@@ -280,7 +280,7 @@ defmodule Mix.SCM.Git do
 
   defp default_into() do
     case Mix.shell() do
-      Mix.Shell.IO -> IO.stream(:stdio, :line)
+      Mix.Shell.IO -> IO.stream()
       _ -> ""
     end
   end

lib/mix/lib/mix/tasks/format.ex

@@ -406,7 +406,7 @@ defmodule Mix.Tasks.Format do
   defp stdin_or_wildcard(path), do: path |> Path.expand() |> Path.wildcard(match_dot: true)
 
   defp read_file(:stdin) do
-    {IO.stream(:stdio, :line) |> Enum.to_list() |> IO.iodata_to_binary(), file: "stdin"}
+    {IO.stream() |> Enum.to_list() |> IO.iodata_to_binary(), file: "stdin"}
   end
 
   defp read_file(file) do