Change to native parallel

Gemfile.lock

@@ -70,7 +70,6 @@ PLATFORMS
 DEPENDENCIES
   mutant!
   mutant-license!
-  parallel (~> 1.3)
   rspec (~> 3.10)
   rspec-core (~> 3.10)
   rspec-its (~> 1.3.0)

mutant.gemspec

@@ -30,7 +30,6 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency('sorbet-runtime', '~> 0.5.0')
   gem.add_runtime_dependency('unparser',       '~> 0.6.9')
 
-  gem.add_development_dependency('parallel',   '~> 1.3')
   gem.add_development_dependency('rspec',      '~> 3.10')
   gem.add_development_dependency('rspec-core', '~> 3.10')
   gem.add_development_dependency('rspec-its',  '~> 1.3.0')

spec/support/corpus.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require 'etc'
 require 'mutant'
 require 'parallel'
 
@@ -25,8 +26,6 @@ class Project
       FINISH_MESSAGE              = 'Mutations - %4i - %s'
       RUBY_GLOB_PATTERN           = '**/*.rb'
 
-      DEFAULT_MUTATION_COUNT = 0
-
       include Adamantium, Anima.new(
         :mutation_coverage,
         :mutation_generation,
@@ -73,6 +72,32 @@ def concurrency_limits
         end
       end
 
+      class Sink
+        include Mutant::Parallel::Sink
+
+        attr_reader :total
+
+        def initialize
+          @total = 0
+        end
+
+        def stop?
+          false
+        end
+
+        def status
+          @total
+        end
+
+        def response(response)
+          if response.error
+            Mutant::WORLD.stderr.puts(response.log)
+            fail response.error
+          end
+          @total += response.result
+        end
+      end
+
       # Verify mutation generation
       #
       # @return [self]
@@ -92,11 +117,32 @@ def verify_mutation_generation
           in_processes: Etc.nprocessors
         }
 
-        total = Parallel.map(effective_ruby_paths, options, &method(:check_generation))
-          .reduce(DEFAULT_MUTATION_COUNT, :+)
+        sink = Sink.new
+
+        parallel_config = Mutant::Parallel::Config.new(
+          block:            method(:check_generation),
+          jobs:             Etc.nprocessors,
+          sink:             sink,
+          timeout:          nil,
+          process_name:     'mutation-generation',
+          source:           Mutant::Parallel::Source::Array.new(jobs: effective_ruby_paths),
+          on_process_start: ->(_) {},
+          thread_name:      'mutation-generation'
+        )
+
+        elapsed = Mutant::WORLD.timer.elapsed do
+          driver = Mutant::Parallel.async(
+            config: parallel_config,
+            world:  Mutant::WORLD
+          )
+
+          loop do
+            status = driver.wait_timeout(1)
+            break if status.done?
+          end
+        end
 
-        took = timer.now - start
-        puts MUTATION_GENERATION_MESSAGE % [total, took, total / took]
+        puts MUTATION_GENERATION_MESSAGE % [sink.total, elapsed, sink.total / elapsed]
         self
       end