[ruby/psych] Make Ractor-ready.

Config is Ractor-local.

Benchmarking reveals that using `Ractor.local_storage` for storing cache
is similar to accessing a constant (~15% slower).

2 files changed, 40 insertions, 6 deletions

diff --git a/lib/psych.rb b/lib/psych.rb
index 0b62362..cedf0a4 100644
--- a/lib/psych.rb
+++ b/lib/psych.rb
@@ -632,9 +632,29 @@ module Psych
   private_class_method :warn_with_uplevel, :parse_caller
 
   class << self
-    attr_accessor :load_tags
-    attr_accessor :dump_tags
-    attr_accessor :domain_types
+    if defined?(Ractor)
+      require 'forwardable'
+      extend Forwardable
+
+      class Config
+        attr_accessor :load_tags, :dump_tags, :domain_types
+        def initialize
+          @load_tags = {}
+          @dump_tags = {}
+          @domain_types = {}
+        end
+      end
+
+      def config
+        Ractor.current[:PsychConfig] ||= Config.new
+      end
+
+      def_delegators :config, :load_tags, :dump_tags, :domain_types, :load_tags=, :dump_tags=, :domain_types=
+    else
+      attr_accessor :load_tags
+      attr_accessor :dump_tags
+      attr_accessor :domain_types
+    end
   end
   self.load_tags = {}
   self.dump_tags = {}
diff --git a/lib/psych/visitors/visitor.rb b/lib/psych/visitors/visitor.rb
index 3f4ba64..35f8f81 100644
--- a/lib/psych/visitors/visitor.rb
+++ b/lib/psych/visitors/visitor.rb
@@ -8,12 +8,26 @@ module Psych
 
       private
 
-      DISPATCH = Hash.new do |hash, klass|
-        hash[klass] = "visit_#{klass.name.gsub('::', '_')}"
+      # @api private
+      def self.dispatch_cache
+        Hash.new do |hash, klass|
+          hash[klass] = :"visit_#{klass.name.gsub('::', '_')}"
+        end
+      end
+
+      if defined?(Ractor)
+        def dispatch
+          Ractor.current[:Psych_Visitors_Visitor] ||= Visitor.dispatch_cache
+        end
+      else
+        DISPATCH = dispatch_cache
+        def dispatch
+          DISPATCH
+        end
       end
 
       def visit target
-        send DISPATCH[target.class], target
+        send dispatch[target.class], target
       end
     end
   end