Execute test runner in a separate process instead of the parallel require

Author: José Valim

lib/elixir/lib/kernel/parallel_require.ex

@@ -32,7 +32,7 @@ defmodule Kernel.ParallelRequire do
       :ok ->
         result
       :error ->
-        IO.puts :stderr, "\nLoading files failed due to warnings while using the --warnings-as-errors option"
+        IO.puts :stderr, "\nExecution failed due to warnings while using the --warnings-as-errors option"
         exit({:shutdown, 1})
     end
   end

lib/elixir/test/elixir/kernel/parallel_require_test.exs

@@ -17,7 +17,7 @@ defmodule Kernel.ParallelRequireTest do
         assert catch_exit(Kernel.ParallelRequire.files fixtures) == {:shutdown, 1}
       end
 
-      assert msg =~ "Loading files failed due to warnings while using the --warnings-as-errors option\n"
+      assert msg =~ "Execution failed due to warnings while using the --warnings-as-errors option\n"
     after
       Code.compiler_options(warnings_as_errors: warnings_as_errors)
     end

lib/mix/lib/mix/compilers/test.ex

@@ -42,20 +42,15 @@ defmodule Mix.Compilers.Test do
 
       test_files ->
         try do
-          spawn_link(fn ->
-            try do
-              Kernel.ParallelRequire.files(test_files, parallel_require_callbacks)
-            catch
-              :error, value ->
-                exit({value, System.stacktrace()})
-              :throw, value ->
-                exit({{:nocatch, value}, System.stacktrace()})
-            after
-              ExUnit.Server.cases_loaded()
-            end
-          end)
-
-          %{failures: failures} = results = ExUnit.run()
+          task = Task.async(ExUnit, :run, [])
+
+          try do
+            Kernel.ParallelRequire.files(test_files, parallel_require_callbacks)
+          after
+            ExUnit.Server.cases_loaded()
+          end
+
+          %{failures: failures} = results = Task.await(task, :infinity)
 
           if failures == 0 do
             agent_write_manifest(stale_manifest_pid)