added unix io type (so now one can open unix sockets), added a basic test to show that connectivity is possible

lib/httpx/io.rb

@@ -250,8 +250,10 @@ module HTTPX
     end
   end
   module IO
+    require "httpx/io/unix"
     extend Registry
     register "tcp", TCP
     register "ssl", SSL
+    register "unix", HTTPX::UNIX
   end
 end

lib/httpx/io/unix.rb

@@ -0,0 +1,55 @@
+require "forwardable"
+
+module HTTPX
+  class UNIX < TCP
+    extend Forwardable
+
+    def_delegator :@uri, :port, :scheme
+
+    def initialize(uri, options)
+      @uri = uri
+      @state = :idle
+      @options = Options.new(options)
+      @path = @options.transport_options[:path]
+      @fallback_protocol = @options.fallback_protocol
+      if @options.io
+        @io = case @options.io
+              when Hash
+                @options.io[@path]
+              else
+                @options.io
+        end
+        unless @io.nil?
+          @keep_open = true
+          @state = :connected
+        end
+      end
+      @io ||= build_socket
+    end
+
+    def hostname
+      @uri.host
+    end
+
+    def connect
+      return unless closed?
+      begin
+        if @io.closed?
+          transition(:idle)
+          @io = build_socket
+        end
+        @io.connect_nonblock(Socket.sockaddr_un(@path))
+      rescue Errno::EISCONN
+      end
+      transition(:connected)
+    rescue Errno::EINPROGRESS,
+           Errno::EALREADY,
+           ::IO::WaitReadable
+    end
+    private
+
+    def build_socket
+      Socket.new(Socket::PF_UNIX, :STREAM, 0)
+    end
+  end
+end

test/io/unix_test.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+require "tempfile"
+require_relative "../test_helper"
+
+class UnixTest < Minitest::Test
+  include HTTPX
+
+  def test_unix_client
+    on_unix_server do |path|
+      client = Client.new(transport: "unix", transport_options: { path: path})
+      response = client.get("http://unix.com/ping")
+      assert response.status == 200, "unexpected code (#{response.status})"
+      assert response.to_s == "pong", "unexpected body (#{response.to_s})"
+      response.close
+      client.close
+    end
+  end
+
+  private
+
+  RESPONSE_HEADER = (<<-HTTP).lines.map.map(&:chomp).join("\r\n") << ("\r\n" * 2)
+HTTP/1.1 200 OK
+Date: Mon, 27 Jul 2009 12:28:53 GMT
+Content-Length: 4
+Content-Type: text/plain
+Connection: close
+  HTTP
+
+  def on_unix_server
+    mutex = Mutex.new
+    resource = ConditionVariable.new
+    path = File.join(Dir.tmpdir, "httpx-unix.sock")
+    server = UNIXServer.new(path)
+    begin
+      th = Thread.start do
+        mutex.synchronize do
+          resource.signal
+        end
+        socket = server.accept
+        socket.readpartial(4096) # drain the socket for the request
+        socket.write(RESPONSE_HEADER)
+        socket.write("pong")
+        socket.close
+      end
+      mutex.synchronize do
+        resource.wait(mutex)
+      end
+      yield server.path
+    ensure
+      server.close
+      File.unlink(path)
+      th.terminate
+    end
+  end
+end