From 0687baaf57ac2fef4ed5406d1a37e05658f8859f Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 14 Oct 2016 13:26:13 +0000
Subject: [PATCH] optparse/kwargs.rb

* lib/optparse/kwargs.rb (OptionParser#define_by_keywords):
  [EXPERIMENTAL] extract command line option definitions from the
  information of keyword arguments.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56423 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog                    |  6 ++++++
 lib/optparse/kwargs.rb       | 17 +++++++++++++++
 test/optparse/test_kwargs.rb | 40 ++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+)
 create mode 100644 lib/optparse/kwargs.rb
 create mode 100644 test/optparse/test_kwargs.rb

diff --git a/ChangeLog b/ChangeLog
index 2b55de6fa9..338bab8527 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri Oct 14 22:26:10 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/optparse/kwargs.rb (OptionParser#define_by_keywords):
+	  [EXPERIMENTAL] extract command line option definitions from the
+	  information of keyword arguments.
+
 Fri Oct 14 18:27:18 2016  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* object.c: Improve documentation for Float conversion.
diff --git a/lib/optparse/kwargs.rb b/lib/optparse/kwargs.rb
new file mode 100644
index 0000000000..ed58cc142b
--- /dev/null
+++ b/lib/optparse/kwargs.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+require 'optparse'
+
+class OptionParser
+  def define_by_keywords(options, meth, **opts)
+    meth.parameters.each do |type, name|
+      case type
+      when :key, :keyreq
+        op, cl = *(type == :key ? %w"[ ]" : ["", ""])
+        define("--#{name}=#{op}#{name.upcase}#{cl}", *opts[name]) do |o|
+          options[name] = o
+        end
+      end
+    end
+    options
+  end
+end
diff --git a/test/optparse/test_kwargs.rb b/test/optparse/test_kwargs.rb
new file mode 100644
index 0000000000..68fe207a2c
--- /dev/null
+++ b/test/optparse/test_kwargs.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: false
+require 'test/unit'
+require 'optparse'
+require 'optparse/kwargs'
+
+class TestOptionParser < Test::Unit::TestCase
+end
+class TestOptionParser::KwArg < Test::Unit::TestCase
+  class K
+    def initialize(host:, port: 8080)
+      @host = host
+      @port = port
+    end
+  end
+
+  class DummyOutput < String
+    alias write <<
+  end
+  def assert_no_error(*args)
+    $stderr, stderr = DummyOutput.new, $stderr
+    assert_nothing_raised(*args) {return yield}
+  ensure
+    stderr, $stderr = $stderr, stderr
+    $!.backtrace.delete_if {|e| /\A#{Regexp.quote(__FILE__)}:#{__LINE__-2}/o =~ e} if $!
+    assert_empty(stderr)
+  end
+  alias no_error assert_no_error
+
+  def test_kwarg
+    opt = OptionParser.new
+    options = opt.define_by_keywords({}, K.instance_method(:initialize),
+                                     port: [Integer])
+    assert_raise(OptionParser::MissingArgument) {opt.parse!(%w"--host")}
+    assert_nothing_raised {opt.parse!(%w"--host=localhost")}
+    assert_equal("localhost", options[:host])
+    assert_nothing_raised {opt.parse!(%w"--port")}
+    assert_nothing_raised {opt.parse!(%w"--port=80")}
+    assert_equal(80, options[:port])
+  end
+end