added xml transcoder

capabilities to encod/decode xml, expects nokogiri.

Gemfile

@@ -23,6 +23,7 @@ group :test do
   else
     gem "webmock"
   end
+  gem "nokogiri"
   gem "websocket-driver"
 
   gem "net-ssh", "~> 4.2.0" if RUBY_VERSION < "2.2.0"

lib/httpx/options.rb

@@ -201,7 +201,7 @@ module HTTPX
     end
 
     %i[
-      params form json body ssl http2_settings
+      params form json xml body ssl http2_settings
       request_class response_class headers_class request_body_class
       response_body_class connection_class options_class
       io fallback_protocol debug debug_level transport_options resolver_class resolver_options
@@ -210,7 +210,7 @@ module HTTPX
       def_option(method_name)
     end
 
-    REQUEST_IVARS = %i[@params @form @json @body].freeze
+    REQUEST_IVARS = %i[@params @form @xml @json @body].freeze
     private_constant :REQUEST_IVARS
 
     def ==(other)

lib/httpx/request.rb

@@ -162,6 +162,8 @@ module HTTPX
           Transcoder.registry("form").encode(options.form)
         elsif options.json
           Transcoder.registry("json").encode(options.json)
+        elsif options.xml
+          Transcoder.registry("xml").encode(options.xml)
         end
         return if @body.nil?
 

lib/httpx/response.rb

@@ -94,6 +94,10 @@ module HTTPX
       decode("form")
     end
 
+    def xml
+      decode("xml")
+    end
+
     private
 
     def decode(format, *args)

lib/httpx/transcoder.rb

@@ -90,4 +90,5 @@ end
 require "httpx/transcoder/body"
 require "httpx/transcoder/form"
 require "httpx/transcoder/json"
+require "httpx/transcoder/xml"
 require "httpx/transcoder/chunker"

lib/httpx/transcoder/xml.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require "delegate"
+require "forwardable"
+require "uri"
+
+module HTTPX::Transcoder
+  module Xml
+    using HTTPX::RegexpExtensions
+
+    module_function
+
+    MIME_TYPES = %r{\b(application|text)/(.+\+)?xml\b}.freeze
+
+    class Encoder < SimpleDelegator
+      def content_type
+        charset = respond_to?(:encoding) ? encoding.to_s.downcase : "utf-8"
+        "application/xml; charset=#{charset}"
+      end
+
+      def bytesize
+        to_s.bytesize
+      end
+    end
+
+    def encode(xml)
+      Encoder.new(xml)
+    end
+
+    begin
+      require "nokogiri"
+
+      # rubocop:disable Lint/DuplicateMethods
+      def decode(response)
+        content_type = response.content_type.mime_type
+
+        raise HTTPX::Error, "invalid form mime type (#{content_type})" unless MIME_TYPES.match?(content_type)
+
+        Nokogiri::XML.method(:parse)
+      end
+    rescue LoadError
+      def decode(_response)
+        raise HTTPX::Error, "\"nokogiri\" is required in order to decode XML"
+      end
+    end
+    # rubocop:enable Lint/DuplicateMethods
+  end
+  register "xml", Xml
+end

test/options_test.rb

@@ -45,7 +45,7 @@ class OptionsTest < Minitest::Test
     assert opt2.body == "fat", "body was not set"
   end
 
-  %i[form json].each do |meth|
+  %i[form json xml].each do |meth|
     define_method :"test_options_#{meth}" do
       opt1 = Options.new
       assert opt1.public_send(meth).nil?, "#{meth} shouldn't be set by default"
@@ -98,6 +98,7 @@ class OptionsTest < Minitest::Test
       :debug_level => 1,
       :params => nil,
       :json => nil,
+      :xml => nil,
       :body => nil,
       :window_size => 16_384,
       :body_threshold_size => 114_688,

test/request_test.rb

@@ -77,6 +77,13 @@ class RequestTest < Minitest::Test
     assert req.headers["content-length"] == "13", "content length is wrong"
   end
 
+  def test_request_body_xml
+    req = Request.new(:post, "http://example.com/", xml: "<xml></xml>")
+    assert !req.body.empty?, "body should exist"
+    assert req.headers["content-type"] == "application/xml; charset=utf-8", "content type is wrong"
+    assert req.headers["content-length"] == "11", "content length is wrong"
+  end
+
   private
 
   def resource

test/response_test.rb

@@ -156,6 +156,11 @@ class ResponseTest < Minitest::Test
     form_response << "богус"
     assert_raises(ArgumentError) { form_response.form }
 
+    xml_response = Response.new(request, 200, "2.0", { "content-type" => "application/xml; charset=utf-8" })
+    xml_response << "<xml></xml>"
+    xml = xml_response.xml
+    assert xml.is_a?(Nokogiri::XML::Node)
+
     form2_response = Response.new(request, 200, "2.0", { "content-type" => "application/x-www-form-urlencoded" })
     form2_response << "a[]=b&a[]=c&d[e]=f&g[h][i][j]=k&l[m][][n]=o&l[m][][p]=q&l[m][][n]=r&s[=t"
     assert form2_response.form == {