added ?download file serve query param support to force file download

CHANGELOG.md

@@ -87,6 +87,8 @@
 - **!** renamed `models.RequestData` to `models.RequestInfo` and soft-deprecated `apis.RequestData(c)` to `apis.RequestInfo(c)` to avoid the stuttering with the `Data` field.
   _The old `apis.RequestData()` method still works to minimize the breaking changes but it is recommended to replace it with `apis.RequestInfo(c)`._
 
+- Added `?download` file query parameter option to instruct the browser to always download a file and not show a preview.
+
 
 ## v0.16.10
 

tools/filesystem/filesystem.go

@@ -321,7 +321,14 @@ var manualExtensionContentTypes = map[string]string{
 	".css": "text/css",      // (see https://github.com/gabriel-vasile/mimetype/pull/113)
 }
 
+// forceAttachmentParam is the name of the request query parameter to
+// force "Content-Disposition: attachment" header.
+const forceAttachmentParam = "download"
+
 // Serve serves the file at fileKey location to an HTTP response.
+//
+// If the `download` query parameter is used the file will be always served for
+// download no matter of its type (aka. with "Content-Disposition: attachment").
 func (s *System) Serve(res http.ResponseWriter, req *http.Request, fileKey string, name string) error {
 	br, readErr := s.bucket.NewReader(s.ctx, fileKey, nil)
 	if readErr != nil {
@@ -329,9 +336,11 @@ func (s *System) Serve(res http.ResponseWriter, req *http.Request, fileKey strin
 	}
 	defer br.Close()
 
+	forceAttachment := req.URL.Query().Has(forceAttachmentParam)
+
 	disposition := "attachment"
 	realContentType := br.ContentType()
-	if list.ExistInSlice(realContentType, inlineServeContentTypes) {
+	if !forceAttachment && list.ExistInSlice(realContentType, inlineServeContentTypes) {
 		disposition = "inline"
 	}
 

tools/filesystem/filesystem_test.go

@@ -257,7 +257,8 @@ func TestFileSystemServe(t *testing.T) {
 	scenarios := []struct {
 		path          string
 		name          string
-		customHeaders map[string]string
+		query         map[string]string
+		headers       map[string]string
 		expectError   bool
 		expectHeaders map[string]string
 	}{
@@ -266,6 +267,7 @@ func TestFileSystemServe(t *testing.T) {
 			"missing.txt",
 			"test_name.txt",
 			nil,
+			nil,
 			true,
 			nil,
 		},
@@ -274,6 +276,7 @@ func TestFileSystemServe(t *testing.T) {
 			"test/sub1.txt",
 			"test_name.txt",
 			nil,
+			nil,
 			false,
 			map[string]string{
 				"Content-Disposition":     "attachment; filename=test_name.txt",
@@ -288,6 +291,7 @@ func TestFileSystemServe(t *testing.T) {
 			"image.png",
 			"test_name.png",
 			nil,
+			nil,
 			false,
 			map[string]string{
 				"Content-Disposition":     "inline; filename=test_name.png",
@@ -297,11 +301,27 @@ func TestFileSystemServe(t *testing.T) {
 				"Cache-Control":           cacheControl,
 			},
 		},
+		{
+			// png with forced attachment
+			"image.png",
+			"test_name_download.png",
+			map[string]string{"download": "12"},
+			nil,
+			false,
+			map[string]string{
+				"Content-Disposition":     "attachment; filename=test_name_download.png",
+				"Content-Type":            "image/png",
+				"Content-Length":          "73",
+				"Content-Security-Policy": csp,
+				"Cache-Control":           cacheControl,
+			},
+		},
 		{
 			// svg exception
 			"image.svg",
 			"test_name.svg",
 			nil,
+			nil,
 			false,
 			map[string]string{
 				"Content-Disposition":     "attachment; filename=test_name.svg",
@@ -316,6 +336,7 @@ func TestFileSystemServe(t *testing.T) {
 			"style.css",
 			"test_name.css",
 			nil,
+			nil,
 			false,
 			map[string]string{
 				"Content-Disposition":     "attachment; filename=test_name.css",
@@ -329,6 +350,7 @@ func TestFileSystemServe(t *testing.T) {
 			// custom header
 			"test/sub2.txt",
 			"test_name.txt",
+			nil,
 			map[string]string{
 				"Content-Disposition":     "1",
 				"Content-Type":            "2",
@@ -353,7 +375,13 @@ func TestFileSystemServe(t *testing.T) {
 		res := httptest.NewRecorder()
 		req := httptest.NewRequest("GET", "/", nil)
 
-		for k, v := range s.customHeaders {
+		query := req.URL.Query()
+		for k, v := range s.query {
+			query.Set(k, v)
+		}
+		req.URL.RawQuery = query.Encode()
+
+		for k, v := range s.headers {
 			res.Header().Set(k, v)
 		}