ensure that stream handler starts response even if there's no data yet

Author: eli-darkly

httphelpers/handlers_streaming.go

@@ -184,6 +184,8 @@ func (s *chunkedStreamingHandlerImpl) ServeHTTP(w http.ResponseWriter, r *http.R
 		flusher.Flush()
 	}
 
+	flusher.Flush()
+
 	var closeNotifyCh <-chan bool
 	// CloseNotifier is deprecated but there's no way to use Context in this case
 	if closeNotifier, ok := w.(http.CloseNotifier); ok { //nolint:megacheck

httphelpers/handlers_streaming_test.go

@@ -13,13 +13,25 @@ import (
 	helpers "github.com/launchdarkly/go-test-helpers/v2"
 )
 
+func TestChunkedStreamingHandlerReturnsResponseBeforeFirstData(t *testing.T) {
+	handler, stream := ChunkedStreamingHandler(nil, "text/plain")
+	defer stream.Close()
+
+	WithServer(handler, func(server *httptest.Server) {
+		resp, err := http.DefaultClient.Get(server.URL)
+		require.NoError(t, err)
+		defer resp.Body.Close()
+		assert.Equal(t, 200, resp.StatusCode)
+	})
+}
+
 func TestChunkedStreamingHandlerSend(t *testing.T) {
 	initialData := []byte("hello,")
 	handler, stream := ChunkedStreamingHandler(initialData, "text/plain")
 	defer stream.Close()
 
 	stream.Enqueue([]byte("first,"))
-	stream.Send([]byte("this isn't sent becauset here are no connections"))
+	stream.Send([]byte("this isn't sent because there are no connections"))
 	stream.Enqueue([]byte("second,"))
 
 	WithServer(handler, func(server *httptest.Server) {