12 files changed, 45 insertions, 24 deletions
diff --git a/lib/uri.rb b/lib/uri.rb
index 5e820f46c3..41b68546a1 100644
--- a/lib/uri.rb
+++ b/lib/uri.rb
@@ -29,8 +29,8 @@
 #   module URI
 #     class RSYNC < Generic
 #       DEFAULT_PORT = 873
+#       URI.refresh_scheme_list
 #     end
-#     @@schemes['RSYNC'] = RSYNC
 #   end
 #   #=> URI::RSYNC
 #
diff --git a/lib/uri/common.rb b/lib/uri/common.rb
index 915c0e9519..ab3234cb37 100644
--- a/lib/uri/common.rb
+++ b/lib/uri/common.rb
@@ -16,6 +16,7 @@ module URI
   REGEXP = RFC2396_REGEXP
   Parser = RFC2396_Parser
   RFC3986_PARSER = RFC3986_Parser.new
+  Ractor.make_shareable(RFC3986_PARSER) if defined?(Ractor)
 
   # URI::Parser.new
   DEFAULT_PARSER = Parser.new
@@ -27,6 +28,7 @@ module URI
   DEFAULT_PARSER.regexp.each_pair do |sym, str|
     const_set(sym, str)
   end
+  Ractor.make_shareable(DEFAULT_PARSER) if defined?(Ractor)
 
   module Util # :nodoc:
     def make_components_hash(klass, array_hash)
@@ -62,10 +64,30 @@ module URI
 
   include REGEXP
 
-  @@schemes = {}
+  SCHEME_LIST_MUTEX = Mutex.new
+  private_constant :SCHEME_LIST_MUTEX
+
   # Returns a Hash of the defined schemes.
+  # The list is lazily calculated.
   def self.scheme_list
-    @@schemes
+    return const_get(:SCHEMES) if defined?(SCHEMES)
+
+    SCHEME_LIST_MUTEX.synchronize do
+      const_set(:SCHEMES, ObjectSpace.
+        each_object(Class).
+        select { |klass| klass < URI::Generic }.
+        each_with_object({}) { |klass, acc| acc[klass.name.split('::').last.upcase] = klass }.
+        freeze)
+    end
+  end
+
+  # Re-calculate scheme list
+  def self.refresh_scheme_list
+    SCHEME_LIST_MUTEX.synchronize do
+      remove_const(:SCHEMES) if defined?(SCHEMES)
+    end
+
+    scheme_list
   end
 
   #
@@ -73,11 +95,7 @@ module URI
   # from +URI.scheme_list+.
   #
   def self.for(scheme, *arguments, default: Generic)
-    if scheme
-      uri_class = @@schemes[scheme.upcase] || default
-    else
-      uri_class = default
-    end
+    uri_class = scheme_list[scheme.to_s.upcase] || default
 
     return uri_class.new(scheme, *arguments)
   end
diff --git a/lib/uri/file.rb b/lib/uri/file.rb
index 561ec703c4..45a7a8b666 100644
--- a/lib/uri/file.rb
+++ b/lib/uri/file.rb
@@ -89,6 +89,4 @@ module URI
     def set_password(v)
     end
   end
-
-  @@schemes['FILE'] = File
 end
diff --git a/lib/uri/ftp.rb b/lib/uri/ftp.rb
index fb38481193..ec8b6e6fe7 100644
--- a/lib/uri/ftp.rb
+++ b/lib/uri/ftp.rb
@@ -262,5 +262,4 @@ module URI
       return str
     end
   end
-  @@schemes['FTP'] = FTP
 end
diff --git a/lib/uri/http.rb b/lib/uri/http.rb
index 70cfb2a1bf..ccd09ddd0c 100644
--- a/lib/uri/http.rb
+++ b/lib/uri/http.rb
@@ -81,7 +81,4 @@ module URI
       url.start_with?(?/.freeze) ? url : ?/ + url
     end
   end
-
-  @@schemes['HTTP'] = HTTP
-
 end
diff --git a/lib/uri/https.rb b/lib/uri/https.rb
index c481b1fe6d..98a08409f6 100644
--- a/lib/uri/https.rb
+++ b/lib/uri/https.rb
@@ -18,5 +18,4 @@ module URI
     # A Default port of 443 for URI::HTTPS
     DEFAULT_PORT = 443
   end
-  @@schemes['HTTPS'] = HTTPS
 end
diff --git a/lib/uri/ldap.rb b/lib/uri/ldap.rb
index 14e6163292..3a0df23213 100644
--- a/lib/uri/ldap.rb
+++ b/lib/uri/ldap.rb
@@ -256,6 +256,4 @@ module URI
       false
     end
   end
-
-  @@schemes['LDAP'] = LDAP
 end
diff --git a/lib/uri/ldaps.rb b/lib/uri/ldaps.rb
index 227e7fab35..fd3f7e875c 100644
--- a/lib/uri/ldaps.rb
+++ b/lib/uri/ldaps.rb
@@ -17,5 +17,4 @@ module URI
     # A Default port of 636 for URI::LDAPS
     DEFAULT_PORT = 636
   end
-  @@schemes['LDAPS'] = LDAPS
 end
diff --git a/lib/uri/mailto.rb b/lib/uri/mailto.rb
index d08c2ae9da..214dea8a86 100644
--- a/lib/uri/mailto.rb
+++ b/lib/uri/mailto.rb
@@ -288,6 +288,4 @@ module URI
     end
     alias to_rfc822text to_mailtext
   end
-
-  @@schemes['MAILTO'] = MailTo
 end
diff --git a/lib/uri/ws.rb b/lib/uri/ws.rb
index 2bfee59003..b846ba208a 100644
--- a/lib/uri/ws.rb
+++ b/lib/uri/ws.rb
@@ -78,7 +78,4 @@ module URI
       url.start_with?(?/.freeze) ? url : ?/ + url
     end
   end
-
-  @@schemes['WS'] = WS
-
 end
diff --git a/lib/uri/wss.rb b/lib/uri/wss.rb
index 1cfa133389..12a53c785e 100644
--- a/lib/uri/wss.rb
+++ b/lib/uri/wss.rb
@@ -18,5 +18,4 @@ module URI
     # A Default port of 443 for URI::WSS
     DEFAULT_PORT = 443
   end
-  @@schemes['WSS'] = WSS
 end
diff --git a/test/uri/test_common.rb b/test/uri/test_common.rb
index 1afa35f93d..311adc0049 100644
--- a/test/uri/test_common.rb
+++ b/test/uri/test_common.rb
@@ -33,6 +33,25 @@ class TestCommon < Test::Unit::TestCase
     end
   end
 
+  def test_ractor
+    return unless defined?(Ractor)
+    r = Ractor.new { URI.parse("https://ruby-lang.org/").inspect }
+    assert_equal(URI.parse("https://ruby-lang.org/").inspect, r.take)
+  end
+
+  def test_register_scheme
+    assert_equal(["FILE", "FTP", "HTTP", "HTTPS", "LDAP", "LDAPS", "MAILTO", "WS"].sort, URI.scheme_list.keys.sort)
+
+    begin
+      URI::Generic.const_set :FOOBAR, Class.new(URI::Generic)
+      URI.refresh_scheme_list
+      assert_equal(["FILE", "FTP", "HTTP", "HTTPS", "LDAP", "LDAPS", "MAILTO", "WS", "FOOBAR"].sort, URI.scheme_list.keys.sort)
+    ensure
+      URI::Generic.send(:remove_const, :FOOBAR)
+      URI.refresh_scheme_list
+    end
+  end
+
   def test_regexp
     EnvUtil.suppress_warning do
       assert_instance_of Regexp, URI.regexp