propagate results of receiving the alt-svc frame, which might arrive just after h2 connection negotiation; for this to be effective, we really have to guarantee negotiation establishment before sending requests, though

lib/httpx/channel.rb

@@ -255,6 +255,10 @@ module HTTPX
         end
         emit(:response, *args)
       end
+      parser.on(:altsvc) do |alt_origin, origin, alt_params|
+        emit(:altsvc, alt_origin, origin, alt_params)
+      end
+
       parser.on(:promise) do |*args|
         emit(:promise, *args)
       end

lib/httpx/channel/http2.rb

@@ -95,7 +95,7 @@ module HTTPX
       @connection.on(:frame_sent, &method(:on_frame_sent))
       @connection.on(:frame_received, &method(:on_frame_received))
       @connection.on(:promise, &method(:on_promise))
-      @connection.on(:altsvc, &method(:on_altsvc))
+      @connection.on(:altsvc) { |frame| on_altsvc(frame[:origin], frame) }
       @connection.on(:settings_ack, &method(:on_settings))
       @connection.on(:goaway, &method(:on_close))
     end
@@ -105,7 +105,7 @@ module HTTPX
       stream.on(:half_close) do
         log(level: 2, label: "#{stream.id}: ") { "waiting for response..." }
       end
-      stream.on(:altsvc, &method(:on_altsvc).curry[request.authority])
+      stream.on(:altsvc, &method(:on_altsvc).curry[request.origin])
       stream.on(:headers, &method(:on_stream_headers).curry[stream, request])
       stream.on(:data, &method(:on_stream_data).curry[stream, request])
     end
@@ -228,14 +228,9 @@ module HTTPX
     def on_altsvc(origin, frame)
       log(level: 2, label: "#{frame[:stream]}: ") { "altsvc frame was received" }
       log(level: 2, label: "#{frame[:stream]}: ") { frame.inspect }
-      origin ||= frame[:origin]
-      alt_proto = frame[:proto]
-      alt_host = frame[:host]
-      alt_port = frame[:port]
-      alt_uri = URI.parse("#{alt_proto}://#{alt_host}:#{alt_port}")
-      log(level: 1, label: "#{frame[:stream]} ") { "#{origin} alt-svc: #{alt_uri}" }
+      alt_origin = URI.parse("#{frame[:proto]}://#{frame[:host]}:#{frame[:port]}")
       params = { "ma" => frame[:max_age] }
-      emit(:alternate_service, alt_uri, origin, params)
+      emit(:altsvc, origin, alt_origin, origin, params)
     end
 
     def on_promise(stream)