CaptureIO now returns an empty string instead of nil when there is no capture

Author: José Valim

CHANGELOG.md

@@ -11,6 +11,7 @@
   * [Kernel] Using ^ inside function clause heads is deprecated, please use a guard instead
 
 * Backwards incompatible changes
+  * [ExUnit] `CaptureIO` returns an empty string instead of nil when there is no capture
   * [Version] The `Version` module now only works with SemVer. The functions `Version.parse/1` and `Version.parse_requirement/1` now return `{:ok,res} | :error` for the cases you want to handle non SemVer cases manually. All other functions will trigger errors on non semantics versions
 
 # v0.12.3 (2014-02-02)

lib/elixir/test/elixir/kernel/warning_test.exs

@@ -91,7 +91,7 @@ defmodule Kernel.WarningTest do
         end
       end
       """
-    end) == nil
+    end) == ""
   after
     purge Sample
   end
@@ -131,7 +131,7 @@ defmodule Kernel.WarningTest do
         defp b(arg1 \\ 1, arg2, arg3 \\ 3), do: [arg1, arg2, arg3]
       end
       """
-    end) == nil
+    end) == ""
   after
     purge [Sample1, Sample2, Sample3, Sample4]
   end
@@ -245,7 +245,7 @@ defmodule Kernel.WarningTest do
         generate
       end
       """
-    end) == nil
+    end) == ""
   after
     purge [Sample1, Sample2]
   end
@@ -292,15 +292,15 @@ defmodule Kernel.WarningTest do
   end
 
   test :used_with_local_with_reattached_overridable do
-    assert nil? capture_err(fn ->
+    assert capture_err(fn ->
       Code.eval_string """
       defmodule Sample do
         def hello, do: world
         defp world, do: :ok
         defoverridable [hello: 0, world: 0]
       end
       """
-    end)
+    end) == ""
   after
     purge Sample
   end

lib/ex_unit/lib/ex_unit/assertions.ex

@@ -306,14 +306,17 @@ defmodule ExUnit.Assertions do
   defp do_assert_receive(expected, timeout, message) do
     binary = Macro.to_string(expected)
 
-    quote do
-      receive do
-        unquote(expected) = received -> unquote(expected) = received
-      after
-        unquote(timeout) ->
-          flunk unquote(message) || "Expected to have received message matching #{unquote binary}"
+    { :receive, meta, args } =
+      quote do
+        receive do
+          unquote(expected) = received -> received
+        after
+          unquote(timeout) ->
+            flunk unquote(message) || "Expected to have received message matching #{unquote binary}"
+        end
       end
-    end
+
+    { :receive, [{:export_all, true}|meta], args }
   end
 
   @doc """

lib/ex_unit/lib/ex_unit/capture_io.ex

@@ -40,8 +40,6 @@ defmodule ExUnit.CaptureIO do
 
       iex> capture_io(fn -> IO.write "josé" end) == "josé"
       true
-      iex> capture_io(fn -> :ok end) == nil
-      true
       iex> capture_io(:stderr, fn -> IO.write(:stderr, "josé") end) == "josé"
       true
       iex> capture_io("this is input", fn ->
@@ -97,7 +95,7 @@ defmodule ExUnit.CaptureIO do
     end
 
     receive do
-      { ^capture_gl, buf } -> buf
+      { ^capture_gl, buf } -> buf || ""
     end
   end
 
@@ -121,7 +119,7 @@ defmodule ExUnit.CaptureIO do
     end
 
     receive do
-      { ^capture_io, buf } -> buf
+      { ^capture_io, buf } -> buf || ""
     end
   end
 

lib/ex_unit/test/ex_unit/capture_io_test.exs

@@ -39,7 +39,7 @@ defmodule ExUnit.CaptureIOTest do
 
   test "with no output" do
     assert capture_io(fn ->
-    end) == nil
+    end) == ""
   end
 
   test "with put chars" do
@@ -82,7 +82,7 @@ defmodule ExUnit.CaptureIOTest do
 
     assert capture_io([capture_prompt: false], fn ->
       :io.get_chars(">", 3)
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert :io.get_chars(">", 3) == :eof
@@ -112,7 +112,7 @@ defmodule ExUnit.CaptureIOTest do
 
     assert capture_io([capture_prompt: false], fn ->
       :io.get_line ">"
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert :io.get_line(">") == :eof
@@ -165,7 +165,7 @@ defmodule ExUnit.CaptureIOTest do
 
     assert capture_io([capture_prompt: false], fn ->
       :io.scan_erl_form('>')
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert :io.scan_erl_form('>') == { :eof, 1 }
@@ -213,7 +213,7 @@ defmodule ExUnit.CaptureIOTest do
   test "with setopts" do
     assert capture_io(fn ->
       :io.setopts({ :encoding, :latin1 })
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert :io.setopts({ :encoding, :latin1 }) == :ok
@@ -223,7 +223,7 @@ defmodule ExUnit.CaptureIOTest do
   test "with getopts" do
     assert capture_io(fn ->
       :io.getopts
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert :io.getopts == { :error, :enotsup }
@@ -233,7 +233,7 @@ defmodule ExUnit.CaptureIOTest do
   test "with columns" do
     assert capture_io(fn ->
       :io.columns
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert :io.columns == { :error, :enotsup }
@@ -243,7 +243,7 @@ defmodule ExUnit.CaptureIOTest do
   test "with rows" do
     assert capture_io(fn ->
       :io.rows
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert :io.rows == { :error, :enotsup }
@@ -265,7 +265,7 @@ defmodule ExUnit.CaptureIOTest do
   test "with unknown io request" do
     assert capture_io(fn ->
       send_and_receive_io(:unknown)
-    end) == nil
+    end) == ""
 
     capture_io(fn ->
       assert send_and_receive_io(:unknown) == { :error, :request }

lib/iex/test/iex/server_test.exs

@@ -43,7 +43,7 @@ defmodule IEx.ServerTest do
   test "does not operate if callback during boot fails" do
     assert capture_io(fn ->
       boot([], fn -> exit(0) end)
-    end) == nil
+    end) == ""
   end
 
   test "take over fails when there is no shell" do