3 files changed, 39 insertions, 2 deletions
diff --git a/lib/optparse/ac.rb b/lib/optparse/ac.rb
index fb0883f97a..9d520101aa 100644
--- a/lib/optparse/ac.rb
+++ b/lib/optparse/ac.rb
@@ -13,6 +13,8 @@ class OptionParser::AC < OptionParser
     end
   end
 
+  ARG_CONV = proc {|val| val.nil? ? true : val}
+
   def _ac_arg_enable(prefix, name, help_string, block)
     _check_ac_args(name, block)
 
@@ -20,8 +22,9 @@ class OptionParser::AC < OptionParser
     ldesc = ["--#{prefix}-#{name}"]
     desc = [help_string]
     q = name.downcase
-    enable = Switch::NoArgument.new(nil, proc {true}, sdesc, ldesc, nil, desc, block)
-    disable = Switch::NoArgument.new(nil, proc {false}, sdesc, ldesc, nil, desc, block)
+    ac_block = proc {|val| block.call(ARG_CONV.call(val))}
+    enable = Switch::PlacedArgument.new(nil, ARG_CONV, sdesc, ldesc, nil, desc, ac_block)
+    disable = Switch::NoArgument.new(nil, proc {false}, sdesc, ldesc, nil, desc, ac_block)
     top.append(enable, [], ["enable-" + q], disable, ['disable-' + q])
     enable
   end
diff --git a/lib/optparse/kwargs.rb b/lib/optparse/kwargs.rb
index ed58cc142b..ccf20c65e9 100644
--- a/lib/optparse/kwargs.rb
+++ b/lib/optparse/kwargs.rb
@@ -2,6 +2,11 @@
 require 'optparse'
 
 class OptionParser
+  # :call-seq:
+  #   define_by_keywords(options, method, **params)
+  #
+  # :include: ../../doc/optparse/creates_option.rdoc
+  #
   def define_by_keywords(options, meth, **opts)
     meth.parameters.each do |type, name|
       case type
diff --git a/lib/optparse/optparse.gemspec b/lib/optparse/optparse.gemspec
new file mode 100644
index 0000000000..ae6596678c
--- /dev/null
+++ b/lib/optparse/optparse.gemspec
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+name = File.basename(__FILE__, ".gemspec")
+version = ["lib", Array.new(name.count("-")+1, "..").join("/")].find do |dir|
+  break File.foreach(File.join(__dir__, dir, "#{name.tr('-', '/')}.rb")) do |line|
+    /^\s*OptionParser::Version\s*=\s*"(.*)"/ =~ line and break $1
+  end rescue nil
+end
+
+Gem::Specification.new do |spec|
+  spec.name          = name
+  spec.version       = version
+  spec.authors       = ["Nobu Nakada"]
+  spec.email         = ["nobu@ruby-lang.org"]
+
+  spec.summary       = %q{OptionParser is a class for command-line option analysis.}
+  spec.description   = %q{OptionParser is a class for command-line option analysis.}
+  spec.homepage      = "https://github.com/ruby/optparse"
+  spec.required_ruby_version = Gem::Requirement.new(">= 2.5.0")
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
+
+  spec.metadata["homepage_uri"] = spec.homepage
+  spec.metadata["source_code_uri"] = spec.homepage
+
+  spec.files         = Dir["{doc,lib,misc}/**/*"] + %w[README.md ChangeLog COPYING]
+  spec.bindir        = "exe"
+  spec.executables   = []
+  spec.require_paths = ["lib"]
+end