From 5d9e6fea71391756871b4b0046b79f88f471eeb2 Mon Sep 17 00:00:00 2001
From: Markus Schirp <mbj@schirp-dso.com>
Date: Fri, 24 Oct 2014 21:34:33 +0000
Subject: [PATCH] Remove parallel use for isolation

* Parallel is not thread save, causing all sorts of issues when nesting.
---
 config/flay.yml                    |  2 +-
 lib/mutant.rb                      |  3 ---
 lib/mutant/isolation.rb            | 18 ++++++++++++++++--
 spec/spec_helper.rb                |  1 +
 spec/unit/mutant/isolation_spec.rb | 20 +++++++++++++++-----
 5 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/config/flay.yml b/config/flay.yml
index 12a5366d..88376657 100644
--- a/config/flay.yml
+++ b/config/flay.yml
@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 1118
+total_score: 1126
diff --git a/lib/mutant.rb b/lib/mutant.rb
index 996cf071..6b7a3eb8 100644
--- a/lib/mutant.rb
+++ b/lib/mutant.rb
@@ -17,9 +17,6 @@ require 'morpher'
 require 'parallel'
 require 'open3'
 
-# Mutant uses parallel with the `:in_threads` option.
-# By default ruby does silently ignore errors raised in threads.
-#
 # This setting is done to make errors within the parallel
 # reporter / execution visible in the main thread.
 Thread.abort_on_exception = true
diff --git a/lib/mutant/isolation.rb b/lib/mutant/isolation.rb
index 7b29eff6..33438b4b 100644
--- a/lib/mutant/isolation.rb
+++ b/lib/mutant/isolation.rb
@@ -38,8 +38,22 @@ module Mutant
       # @api private
       #
       def self.call(&block)
-        Parallel.map([block], in_processes: 1, &block.method(:call)).first
-      rescue Parallel::DeadWorker => exception
+        reader, writer = IO.pipe
+
+        pid = fork do
+          File.open('/dev/null', 'w') do |file|
+            $stderr.reopen(file)
+            reader.close
+            writer.write(Marshal.dump(block.call))
+            writer.close
+          end
+        end
+
+        writer.close
+        result = Marshal.load(reader.read)
+        Process.waitpid(pid)
+        result
+      rescue => exception
         fail Error, exception
       end
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 302fcc02..c0202ef4 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -16,6 +16,7 @@ if ENV['COVERAGE'] == 'true'
   end
 end
 
+require 'tempfile'
 require 'concord'
 require 'adamantium'
 require 'devtools/spec_helper'
diff --git a/spec/unit/mutant/isolation_spec.rb b/spec/unit/mutant/isolation_spec.rb
index 0649b805..b7fb4f41 100644
--- a/spec/unit/mutant/isolation_spec.rb
+++ b/spec/unit/mutant/isolation_spec.rb
@@ -39,19 +39,29 @@ RSpec.describe Mutant::Isolation::Fork do
       expect(object.call { :foo }).to be(:foo)
     end
 
-    it 'wraps Parallel::DeadWorker exceptions' do
-      expect { object.call { fail Parallel::DeadWorker } }.to raise_error(Mutant::Isolation::Error)
+    it 'wraps exceptions' do
+      expect { object.call { fail } }.to raise_error(Mutant::Isolation::Error)
     end
 
-    it 'wraps Parallel::DeadWorker exceptions caused by crashing ruby' do
+    it 'wraps exceptions caused by crashing ruby' do
       expect do
         object.call do
-          # Silence rb_bug writes
-          $stderr.reopen(File.open('/dev/null', 'w'))
           fail RbBug.call
         end
       end.to raise_error(Mutant::Isolation::Error)
     end
 
+    it 'redirects $stderr of children to /dev/null' do
+      begin
+        Tempfile.open('mutant-test') do |file|
+          $stderr = file
+          object.call { $stderr.puts('test') }
+          file.rewind
+          expect(file.read).to eql('')
+        end
+      ensure
+        $stderr = STDERR
+      end
+    end
   end
 end