Do not set the content-type when response has no body (#1013)

gzhttp/compress.go

@@ -131,15 +131,15 @@ func (w *GzipResponseWriter) Write(b []byte) (int, error) {
 
  // If the Content-Length is larger than minSize or the current buffer is larger than minSize, then continue.
  if cl >= w.minSize || len(w.buf) >= w.minSize {
- // If a Content-Type wasn't specified, infer it from the current buffer.
- if ct == "" {
+ // If a Content-Type wasn't specified, infer it from the current buffer when the response has a body.
+ if ct == "" && bodyAllowedForStatus(w.code) && len(w.buf) > 0 {
  ct = http.DetectContentType(w.buf)
- }
 
- // Handles the intended case of setting a nil Content-Type (as for http/server or http/fs)
- // Set the header only if the key does not exist
- if _, ok := hdr[contentType]; w.setContentType && !ok {
- hdr.Set(contentType, ct)
+ // Handles the intended case of setting a nil Content-Type (as for http/server or http/fs)
+ // Set the header only if the key does not exist
+ if _, ok := hdr[contentType]; w.setContentType && !ok {
+ hdr.Set(contentType, ct)
+ }
  }
 
  // If the Content-Type is acceptable to GZIP, initialize the GZIP writer.
@@ -349,12 +349,14 @@ func (w *GzipResponseWriter) Close() error {
  ce = w.Header().Get(contentEncoding)
  cr = w.Header().Get(contentRange)
  )
- if ct == "" {
+
+ // Detects the response content-type when it does not exist and the response has a body.
+ if ct == "" && bodyAllowedForStatus(w.code) && len(w.buf) > 0 {
  ct = http.DetectContentType(w.buf)
 
  // Handles the intended case of setting a nil Content-Type (as for http/server or http/fs)
  // Set the header only if the key does not exist
- if _, ok := w.Header()[contentType]; bodyAllowedForStatus(w.code) && w.setContentType && !ok {
+ if _, ok := w.Header()[contentType]; w.setContentType && !ok {
  w.Header().Set(contentType, ct)
  }
  }
@@ -393,7 +395,8 @@ func (w *GzipResponseWriter) Flush() {
  cr = w.Header().Get(contentRange)
  )
 
- if ct == "" {
+ // Detects the response content-type when it does not exist and the response has a body.
+ if ct == "" && bodyAllowedForStatus(w.code) && len(w.buf) > 0 {
  ct = http.DetectContentType(w.buf)
 
  // Handles the intended case of setting a nil Content-Type (as for http/server or http/fs)

gzhttp/compress_test.go

@@ -1617,6 +1617,25 @@ func TestNoContentTypeWhenNoContent(t *testing.T) {
 
 }
 
+func TestNoContentTypeWhenNoBody(t *testing.T) {
+ handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+ w.WriteHeader(http.StatusOK)
+ })
+
+ wrapper, err := NewWrapper()
+ assertNil(t, err)
+
+ req, _ := http.NewRequest("GET", "/", nil)
+ req.Header.Set("Accept-Encoding", "gzip")
+ resp := httptest.NewRecorder()
+ wrapper(handler).ServeHTTP(resp, req)
+ res := resp.Result()
+
+ assertEqual(t, http.StatusOK, res.StatusCode)
+ assertEqual(t, "", res.Header.Get("Content-Type"))
+
+}
+
 func TestContentTypeDetect(t *testing.T) {
  for _, tt := range sniffTests {
  t.Run(tt.desc, func(t *testing.T) {