mix test --listen-on-stdin (#4921)

Signed-off-by: José Valim <[email protected]>

Author: ericentin

lib/mix/lib/mix/tasks/test.ex

@@ -67,6 +67,9 @@ defmodule Mix.Tasks.Test do
     * `--no-elixir-version-check` - do not check the Elixir version from mix.exs
     * `--stale` - run only tests which reference modules that changed since the
       last `test --stale`. You can read more about this option in the "Stale" section below.
+    * `--listen-on-stdin` - run tests, and then listen on stdin. Receiving a newline will
+      result in the tests being run again. Very useful when combined with `--stale` and
+      external commands which produce output on stdout upon file system modification.
 
   ## Filters
 
@@ -164,7 +167,7 @@ defmodule Mix.Tasks.Test do
              exclude: :keep, seed: :integer, only: :keep, compile: :boolean,
              start: :boolean, timeout: :integer, raise: :boolean,
              deps_check: :boolean, archives_check: :boolean, elixir_version_check: :boolean,
-             stale: :boolean]
+             stale: :boolean, listen_on_stdin: :boolean]
 
   @cover [output: "cover", tool: Cover]
 
@@ -243,6 +246,13 @@ defmodule Mix.Tasks.Test do
       :noop ->
         :ok
     end
+
+    if opts[:listen_on_stdin] do
+      IO.gets(:stdio, "")
+      Mix.shell.info "Restarting..."
+      :init.restart()
+      :timer.sleep(:infinity)
+    end
   end
 
   defp display_warn_test_pattern(files, pattern) do

lib/mix/test/mix/tasks/test_test.exs

@@ -104,6 +104,32 @@ defmodule Mix.Tasks.TestTest do
     end
   end
 
+  test "--listen-on-stdin: runs tests after input" do
+    in_fixture "test_stale", fn ->
+      port = mix_port(~w[test --stale --listen-on-stdin])
+
+      assert receive_until_match(port, "seed", []) =~ "2 tests"
+
+      :erlang.port_command(port, "\n")
+
+      assert receive_until_match(port, "No stale tests.", []) =~ "Restarting..."
+    end
+  end
+
+  defp receive_until_match(port, expected, acc) do
+    receive do
+      {^port, {:data, charlist}} ->
+        string = to_string(charlist)
+        acc = [acc | string]
+
+        if string =~ expected do
+          IO.iodata_to_binary(acc)
+        else
+          receive_until_match(port, expected, acc)
+        end
+    end
+  end
+
   defp set_all_mtimes(time \\ {{2010, 1, 1}, {0, 0, 0}}) do
     Enum.each(Path.wildcard("**", match_dot: true), &File.touch!(&1, time))
   end

lib/mix/test/test_helper.exs

@@ -136,6 +136,15 @@ defmodule MixTest.Case do
                env: envs) |> elem(0)
   end
 
+  def mix_port(args, envs \\ []) when is_list(args) do
+    :erlang.open_port({:spawn_executable, elixir_executable()}, [
+      {:args, ["-r", mix_executable(), "--" | args]},
+      {:env, envs},
+      :use_stdio,
+      :stderr_to_stdout
+    ])
+  end
+
   defp mix_executable do
     Path.expand("../../../bin/mix", __DIR__)
   end