[ruby/uri] Revert "Fix to support Ruby 3.0 Ractor"

* This reverts commit 1faa4fdc161d7aeebdb5de0c407b923beaecf898.
* It has too many problems, see https://github.com/ruby/uri/pull/22 for discussion.

https://github.com/ruby/uri/commit/b959da2dc9

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
 #

lib/uri/common.rb

@@ -16,7 +16,6 @@ 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
@@ -28,7 +27,6 @@ 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)
@@ -64,30 +62,10 @@ module URI
 
   include REGEXP
 
-  SCHEME_LIST_MUTEX = Mutex.new
-  private_constant :SCHEME_LIST_MUTEX
-
+  @@schemes = {}
   # Returns a Hash of the defined schemes.
-  # The list is lazily calculated.
   def self.scheme_list
-    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
+    @@schemes
   end
 
   #
@@ -95,7 +73,11 @@ module URI
   # from +URI.scheme_list+.
   #
   def self.for(scheme, *arguments, default: Generic)
-    uri_class = scheme_list[scheme.to_s.upcase] || default
+    if scheme
+      uri_class = @@schemes[scheme.upcase] || default
+    else
+      uri_class = default
+    end
 
     return uri_class.new(scheme, *arguments)
   end

lib/uri/file.rb

@@ -89,4 +89,6 @@ module URI
     def set_password(v)
     end
   end
+
+  @@schemes['FILE'] = File
 end

lib/uri/ftp.rb

@@ -262,4 +262,5 @@ module URI
       return str
     end
   end
+  @@schemes['FTP'] = FTP
 end

lib/uri/http.rb

@@ -81,4 +81,7 @@ module URI
       url.start_with?(?/.freeze) ? url : ?/ + url
     end
   end
+
+  @@schemes['HTTP'] = HTTP
+
 end

lib/uri/https.rb

@@ -18,4 +18,5 @@ module URI
     # A Default port of 443 for URI::HTTPS
     DEFAULT_PORT = 443
   end
+  @@schemes['HTTPS'] = HTTPS
 end

lib/uri/ldap.rb

@@ -256,4 +256,6 @@ module URI
       false
     end
   end
+
+  @@schemes['LDAP'] = LDAP
 end

lib/uri/ldaps.rb

@@ -17,4 +17,5 @@ module URI
     # A Default port of 636 for URI::LDAPS
     DEFAULT_PORT = 636
   end
+  @@schemes['LDAPS'] = LDAPS
 end

lib/uri/mailto.rb

@@ -288,4 +288,6 @@ module URI
     end
     alias to_rfc822text to_mailtext
   end
+
+  @@schemes['MAILTO'] = MailTo
 end

lib/uri/ws.rb

@@ -78,4 +78,7 @@ module URI
       url.start_with?(?/.freeze) ? url : ?/ + url
     end
   end
+
+  @@schemes['WS'] = WS
+
 end

lib/uri/wss.rb

@@ -18,4 +18,5 @@ module URI
     # A Default port of 443 for URI::WSS
     DEFAULT_PORT = 443
   end
+  @@schemes['WSS'] = WSS
 end

test/uri/test_common.rb

@@ -33,25 +33,6 @@ 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