Gzip: Fix for wrong content-type when templates is used.

middleware/gzip/gzip.go

@@ -121,12 +121,12 @@ func (w *gzipResponseWriter) WriteHeader(code int) {
 
 // Write wraps the underlying Write method to do compression.
 func (w *gzipResponseWriter) Write(b []byte) (int, error) {
-	if !w.statusCodeWritten {
-		w.WriteHeader(http.StatusOK)
-	}
 	if w.Header().Get("Content-Type") == "" {
 		w.Header().Set("Content-Type", http.DetectContentType(b))
 	}
+	if !w.statusCodeWritten {
+		w.WriteHeader(http.StatusOK)
+	}
 	n, err := w.Writer.Write(b)
 	return n, err
 }

middleware/gzip/gzip_test.go

@@ -2,8 +2,10 @@ package gzip
 
 import (
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 
 	"github.com/mholt/caddy/middleware"
@@ -80,7 +82,16 @@ func TestGzipHandler(t *testing.T) {
 
 func nextFunc(shouldGzip bool) middleware.Handler {
 	return middleware.HandlerFunc(func(w http.ResponseWriter, r *http.Request) (int, error) {
-		w.Write([]byte("test"))
+
+		// write a relatively large text file
+		b, err := ioutil.ReadFile("testdata/test.txt")
+		if err != nil {
+			return 500, err
+		}
+		if _, err := w.Write(b); err != nil {
+			return 500, err
+		}
+
 		if shouldGzip {
 			if r.Header.Get("Accept-Encoding") != "" {
 				return 0, fmt.Errorf("Accept-Encoding header not expected")
@@ -94,6 +105,9 @@ func nextFunc(shouldGzip bool) middleware.Handler {
 			if _, ok := w.(*gzipResponseWriter); !ok {
 				return 0, fmt.Errorf("ResponseWriter should be gzipResponseWriter, found %T", w)
 			}
+			if strings.Contains(w.Header().Get("Content-Type"), "application/x-gzip") {
+				return 0, fmt.Errorf("Content type should not be gzip.")
+			}
 			return 0, nil
 		}
 		if r.Header.Get("Accept-Encoding") == "" {