When gzipping file responses add header for uncompressed content length (#10836)

api4/file.go

@@ -546,7 +546,7 @@ func getFile(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 	defer fileReader.Close()
 
-	err = writeFileResponse(info.Name, info.MimeType, info.Size, fileReader, forceDownload, w, r)
+	err = writeFileResponse(info.Name, info.MimeType, info.Size, *c.App.Config().ServiceSettings.WebserverMode, fileReader, forceDownload, w, r)
 	if err != nil {
 		c.Err = err
 		return
@@ -588,7 +588,7 @@ func getFileThumbnail(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 	defer fileReader.Close()
 
-	err = writeFileResponse(info.Name, THUMBNAIL_IMAGE_TYPE, 0, fileReader, forceDownload, w, r)
+	err = writeFileResponse(info.Name, THUMBNAIL_IMAGE_TYPE, 0, *c.App.Config().ServiceSettings.WebserverMode, fileReader, forceDownload, w, r)
 	if err != nil {
 		c.Err = err
 		return
@@ -663,7 +663,7 @@ func getFilePreview(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 	defer fileReader.Close()
 
-	err = writeFileResponse(info.Name, PREVIEW_IMAGE_TYPE, 0, fileReader, forceDownload, w, r)
+	err = writeFileResponse(info.Name, PREVIEW_IMAGE_TYPE, 0, *c.App.Config().ServiceSettings.WebserverMode, fileReader, forceDownload, w, r)
 	if err != nil {
 		c.Err = err
 		return
@@ -729,19 +729,24 @@ func getPublicFile(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 	defer fileReader.Close()
 
-	err = writeFileResponse(info.Name, info.MimeType, info.Size, fileReader, false, w, r)
+	err = writeFileResponse(info.Name, info.MimeType, info.Size, *c.App.Config().ServiceSettings.WebserverMode, fileReader, false, w, r)
 	if err != nil {
 		c.Err = err
 		return
 	}
 }
 
-func writeFileResponse(filename string, contentType string, contentSize int64, fileReader io.Reader, forceDownload bool, w http.ResponseWriter, r *http.Request) *model.AppError {
+func writeFileResponse(filename string, contentType string, contentSize int64, webserverMode string, fileReader io.Reader, forceDownload bool, w http.ResponseWriter, r *http.Request) *model.AppError {
 	w.Header().Set("Cache-Control", "max-age=2592000, private")
 	w.Header().Set("X-Content-Type-Options", "nosniff")
 
 	if contentSize > 0 {
-		w.Header().Set("Content-Length", strconv.Itoa(int(contentSize)))
+		contentSizeStr := strconv.Itoa(int(contentSize))
+		if webserverMode == "gzip" {
+			w.Header().Set("X-Uncompressed-Content-Length", contentSizeStr)
+		} else {
+			w.Header().Set("Content-Length", contentSizeStr)
+		}
 	}
 
 	if contentType == "" {