From a2dd8d846da9648aa74b266337429a0ab53d7bd3 Mon Sep 17 00:00:00 2001
From: Marc-Andre Lafortune <github@marc-andre.ca>
Date: Tue, 22 Dec 2020 21:29:00 -0500
Subject: [PATCH] [ruby/psych] Optimize cache with `compare_by_identity`

Using `compare_by_identity` gives a 4x performance boost on cache hits.
Benchmark in https://github.com/JuanitoFatas/fast-ruby/issues/189
---
 lib/psych/visitors/visitor.rb   | 2 +-
 lib/psych/visitors/yaml_tree.rb | 2 +-
 test/psych/test_ractor.rb       | 3 +++
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/psych/visitors/visitor.rb b/lib/psych/visitors/visitor.rb
index 35f8f81f..e2585c0c 100644
--- a/lib/psych/visitors/visitor.rb
+++ b/lib/psych/visitors/visitor.rb
@@ -12,7 +12,7 @@ def accept target
       def self.dispatch_cache
         Hash.new do |hash, klass|
           hash[klass] = :"visit_#{klass.name.gsub('::', '_')}"
-        end
+        end.compare_by_identity
       end
 
       if defined?(Ractor)
diff --git a/lib/psych/visitors/yaml_tree.rb b/lib/psych/visitors/yaml_tree.rb
index 986c57be..ac6777ae 100644
--- a/lib/psych/visitors/yaml_tree.rb
+++ b/lib/psych/visitors/yaml_tree.rb
@@ -80,7 +80,7 @@ def initialize emitter, ss, options
           raise(TypeError, "Can't dump #{target.class}") unless method
 
           h[klass] = method
-        end
+        end.compare_by_identity
       end
 
       def start encoding = Nodes::Stream::UTF8
diff --git a/test/psych/test_ractor.rb b/test/psych/test_ractor.rb
index 90e40360..2f8d5ca1 100644
--- a/test/psych/test_ractor.rb
+++ b/test/psych/test_ractor.rb
@@ -24,6 +24,9 @@ def test_not_shareable
   end
 
   def test_ractor_config
+    # Config is ractor-local
+    # Test is to make sure it works, even though usage is probably very low.
+    # The methods are not documented and might be deprecated one day
     assert_ractor(<<~RUBY, require_relative: 'helper')
       r = Ractor.new do
         Psych.add_builtin_type 'omap' do |type, val|