server_connection: fix regression which caused wakeup_writer bookke…

…eping to be wrong for async responses (inhabitedtype#37)

Introduced in inhabitedtype#161

CHANGES.md

@@ -55,6 +55,11 @@ Unreleased
   [inhabitedtype/httpaf#162](https://github.com/inhabitedtype/httpaf/issues/162)
 - httpaf-async: Add HTTPS support for the Async bindings
   ([#35](https://github.com/anmonteiro/httpaf/pull/35)).
+- httpaf: Fix upstream regression introduced in
+  [inhabitedtype/httpaf#161](https://github.com/inhabitedtype/httpaf/pull/161)
+  that caused `wake_up_writer` callback bookkeeping to be slightly wrong due to
+  physical equality, producing runtime errors in cases where it shouldn't
+  ([#37](https://github.com/anmonteiro/httpaf/pull/37)).
 
 httpaf (upstream) 0.6.5
 --------------

lib_test/test_server_connection.ml

@@ -723,6 +723,28 @@ let test_empty_body_no_immediate_flush () =
     true !reader_woken_up;
 ;;
 
+let test_yield_before_starting_a_response () =
+  let reader_woken_up = ref false in
+  let response = Response.create `OK in
+  let continue_response = ref (fun () -> ()) in
+  let request_handler reqd =
+    continue_response := (fun () ->
+      let resp_body = Reqd.respond_with_streaming reqd response in
+      Body.close_writer resp_body)
+  in
+  let t = create ~error_handler request_handler in
+  reader_ready t;
+  writer_yielded t;
+  read_request t (Request.create `GET "/");
+  yield_reader t (fun () -> reader_woken_up := true);
+  yield_writer t ignore;
+  !continue_response ();
+  write_response t ~body:"" response;
+  writer_yielded t;
+  Alcotest.(check bool) "Reader woken up"
+    true !reader_woken_up;
+;;
+
 let tests =
   [ "initial reader state"  , `Quick, test_initial_reader_state
   ; "shutdown reader closed", `Quick, test_reader_is_closed_after_eof
@@ -750,4 +772,5 @@ let tests =
   ; "malformed request, streaming response", `Quick, test_malformed_request_streaming_error_response
   ; "`flush_headers_immediately` with empty body", `Quick, test_immediate_flush_empty_body
   ; "empty body with no immediate flush", `Quick, test_empty_body_no_immediate_flush
+  ; "yield before starting a response", `Quick, test_yield_before_starting_a_response
   ]