allow debug option, which can be passed the logger (must respond to #<<); using it in the debug logger for http1 payload and http2 frames

lib/httpx/channel/http1.rb

@@ -147,8 +147,8 @@ module HTTPX
     end
 
     def log(&msg)
-      return unless $HTTPX_DEBUG
-      $stderr << (+"" << msg.call << "\n")
+      return unless @options.debug 
+      @options.debug << (+"" << msg.call << "\n")
     end
   end
   Channel.register "http/1.1", Channel::HTTP1

lib/httpx/channel/http2.rb

@@ -176,8 +176,8 @@ module HTTPX
     end
 
     def log(&msg)
-      return unless $HTTPX_DEBUG
-      $stderr << (+"connection (HTTP/2): " << msg.call << "\n")
+      return unless @options.debug 
+      @options.debug << (+"connection (HTTP/2): " << msg.call << "\n")
     end
   end
   Channel.register "h2", Channel::HTTP2

lib/httpx/io.rb

@@ -97,6 +97,10 @@ module HTTPX
       !@keep_open && !@connected
     end
 
+    def inspect
+      "#<#{self.class}#{@io.fileno}: #{@ip}:#{@port}>"
+    end
+
     private
 
     def build_socket
@@ -105,8 +109,8 @@ module HTTPX
     end
     
     def log(&msg)
-      return unless $HTTPX_DEBUG
-      $stderr << (+"io: " << msg.call << "\n")
+      return unless @options.debug 
+      @options.debug << (+"#{inspect}: " << msg.call << "\n")
     end
   end
 

lib/httpx/options.rb

@@ -41,6 +41,7 @@ module HTTPX
 
     def initialize(options = {})
       defaults = {
+        :debug                    => ENV.key?("HTTPX_DEBUG") ? $stderr : nil,
         :proxy                    => {},
         :ssl                      => { alpn_protocols: %w[h2 http/1.1] },
         :fallback_protocol        => "http/1.1", 
@@ -95,7 +96,7 @@ module HTTPX
       params form json body
       proxy follow ssl max_retries
       request_class response_class headers_class response_body_class
-      io fallback_protocol
+      io fallback_protocol debug
     ].each do |method_name|
       def_option(method_name)
     end

test/options_test.rb

@@ -57,7 +57,8 @@ class OptionsSpec < Minitest::Test
 
 
     assert foo.merge(bar).to_hash == {
-      :io                 => nil,
+      :io                 => ENV.key?("HTTPX_DEBUG") ? $stderr : nil,
+      :debug              => nil,
       :params             => nil,
       :json               => nil,
       :body               => nil,