[rubygems/rubygems] Copy YAMLSerializer from Bundler

https://github.com/rubygems/rubygems/commit/6a97346708

lib/rubygems/config_file.rb

@@ -517,14 +517,14 @@ if you believe they were disclosed to a third party.
       k.is_a?(Symbol) ? ":#{k}" : k
     end
 
-    require "bundler/yaml_serializer"
-    Bundler::YAMLSerializer.dump(content)
+    require_relative "yaml_serializer"
+    Gem::YAMLSerializer.dump(content)
   end
 
   def self.load_with_rubygems_config_hash(yaml)
-    require "bundler/yaml_serializer"
+    require_relative "yaml_serializer"
 
-    content = Bundler::YAMLSerializer.load(yaml)
+    content = Gem::YAMLSerializer.load(yaml)
 
     content.transform_keys! do |k|
       if k.match?(/\A:(.*)\Z/)

lib/rubygems/yaml_serializer.rb

@@ -0,0 +1,89 @@
+# frozen_string_literal: true
+
+module Gem
+  # A stub yaml serializer that can handle only hashes and strings (as of now).
+  module YAMLSerializer
+    module_function
+
+    def dump(hash)
+      yaml = String.new("---")
+      yaml << dump_hash(hash)
+    end
+
+    def dump_hash(hash)
+      yaml = String.new("\n")
+      hash.each do |k, v|
+        yaml << k << ":"
+        if v.is_a?(Hash)
+          yaml << dump_hash(v).gsub(/^(?!$)/, "  ") # indent all non-empty lines
+        elsif v.is_a?(Array) # Expected to be array of strings
+          yaml << "\n- " << v.map {|s| s.to_s.gsub(/\s+/, " ").inspect }.join("\n- ") << "\n"
+        else
+          yaml << " " << v.to_s.gsub(/\s+/, " ").inspect << "\n"
+        end
+      end
+      yaml
+    end
+
+    ARRAY_REGEX = /
+      ^
+      (?:[ ]*-[ ]) # '- ' before array items
+      (['"]?) # optional opening quote
+      (.*) # value
+      \1 # matching closing quote
+      $
+    /xo.freeze
+
+    HASH_REGEX = /
+      ^
+      ([ ]*) # indentations
+      (.+) # key
+      (?::(?=(?:\s|$))) # :  (without the lookahead the #key includes this when : is present in value)
+      [ ]?
+      (['"]?) # optional opening quote
+      (.*) # value
+      \3 # matching closing quote
+      $
+    /xo.freeze
+
+    def load(str)
+      res = {}
+      stack = [res]
+      last_hash = nil
+      last_empty_key = nil
+      str.split(/\r?\n/).each do |line|
+        if match = HASH_REGEX.match(line)
+          indent, key, quote, val = match.captures
+          key = convert_to_backward_compatible_key(key)
+          depth = indent.scan(/  /).length
+          if quote.empty? && val.empty?
+            new_hash = {}
+            stack[depth][key] = new_hash
+            stack[depth + 1] = new_hash
+            last_empty_key = key
+            last_hash = stack[depth]
+          else
+            stack[depth][key] = val
+          end
+        elsif match = ARRAY_REGEX.match(line)
+          _, val = match.captures
+          last_hash[last_empty_key] = [] unless last_hash[last_empty_key].is_a?(Array)
+
+          last_hash[last_empty_key].push(val)
+        end
+      end
+      res
+    end
+
+    # for settings' keys
+    def convert_to_backward_compatible_key(key)
+      key = "#{key}/" if key =~ /https?:/i && key !~ %r{/\Z}
+      key = key.gsub(".", "__") if key.include?(".")
+      key
+    end
+
+    class << self
+      private :dump_hash, :convert_to_backward_compatible_key
+    end
+  end
+end