Stop encoding HTML (prebid#236)

* Fixed the encoding bug.

* Added newline.

endpoints/openrtb2/auction.go

@@ -11,6 +11,7 @@ import (
 	"errors"
 	"github.com/prebid/prebid-server/openrtb_ext"
 	"time"
+	"github.com/golang/glog"
 )
 
 func NewEndpoint(ex exchange.Exchange, validator openrtb_ext.BidderParamValidator) (httprouter.Handle, error) {
@@ -46,14 +47,16 @@ func (deps *endpointDeps) Auction(w http.ResponseWriter, r *http.Request, _ http
 		return
 	}
 
-	responseBytes, err := json.Marshal(response)
-	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		fmt.Fprintf(w, "Failed to marshal auction response: %v", err)
-	}
+	// Fixes #231
+	enc := json.NewEncoder(w)
+	enc.SetEscapeHTML(false)
 
-	w.WriteHeader(200)
-	w.Write(responseBytes)
+	// If an error happens when encoding the response, there isn't much we can do.
+	// If we've sent _any_ bytes, then Go would have sent the 200 status code first.
+	// That status code can't be un-sent... so the best we can do is log the error.
+	if err := enc.Encode(response); err != nil {
+		glog.Errorf("/openrtb2/auction Error encoding response: %v", err)
+	}
 }
 
 // parseRequest turns the HTTP request into an OpenRTB request.

endpoints/openrtb2/auction_test.go

@@ -86,6 +86,19 @@ func TestExchangeError(t *testing.T) {
 	}
 }
 
+
+// TestNoEncoding prevents #231.
+func TestNoEncoding(t *testing.T) {
+	endpoint, _ := NewEndpoint(&mockExchange{}, &bidderParamValidator{})
+	request := httptest.NewRequest("POST", "/openrtb2/auction", strings.NewReader(validRequests[0]))
+	recorder := httptest.NewRecorder()
+	endpoint(recorder, request, nil)
+
+	if !strings.Contains(recorder.Body.String(), "<script></script>") {
+		t.Errorf("The Response from the exchange should not be html-encoded")
+	}
+}
+
 // nobidExchange is a well-behaved exchange which always bids "no bid".
 type nobidExchange struct {}
 
@@ -283,3 +296,15 @@ var invalidRequests = []string{
 		}
 	}]}`,
 }
+
+type mockExchange struct {}
+
+func (*mockExchange) HoldAuction(ctx context.Context, bidRequest *openrtb.BidRequest) (*openrtb.BidResponse, error) {
+	return &openrtb.BidResponse{
+		SeatBid: []openrtb.SeatBid{{
+			Bid: []openrtb.Bid{{
+				AdM: "<script></script>",
+			}},
+		}},
+	}, nil
+}