feat attachment filename support utf8

https://datatracker.ietf.org/doc/html/rfc5987
https://stackoverflow.com/questions/93551/how-to-encode-the-filename-parameter-of-content-disposition-header-in-http
https://stackoverflow.com/questions/53069040/checking-a-string-contains-only-ascii-characters

Author: a-wing

context.go

@@ -6,7 +6,6 @@ package gin
 
 import (
 	"errors"
-	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
@@ -1018,7 +1017,11 @@ func (c *Context) FileFromFS(filepath string, fs http.FileSystem) {
 // FileAttachment writes the specified file into the body stream in an efficient way
 // On the client side, the file will typically be downloaded with the given filename
 func (c *Context) FileAttachment(filepath, filename string) {
-	c.Writer.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))
+	if isASCII(filename) {
+		c.Writer.Header().Set("Content-Disposition", `attachment; filename="`+filename+`"`)
+	} else {
+		c.Writer.Header().Set("Content-Disposition", `attachment; filename*=UTF-8''`+url.QueryEscape(filename))
+	}
 	http.ServeFile(c.Writer, c.Request, filepath)
 }
 

context_test.go

@@ -15,6 +15,7 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"os"
 	"reflect"
 	"strings"
@@ -1033,6 +1034,19 @@ func TestContextRenderAttachment(t *testing.T) {
 	assert.Equal(t, fmt.Sprintf("attachment; filename=\"%s\"", newFilename), w.Header().Get("Content-Disposition"))
 }
 
+func TestContextRenderUTF8Attachment(t *testing.T) {
+	w := httptest.NewRecorder()
+	c, _ := CreateTestContext(w)
+	newFilename := "new🧡_filename.go"
+
+	c.Request, _ = http.NewRequest("GET", "/", nil)
+	c.FileAttachment("./gin.go", newFilename)
+
+	assert.Equal(t, 200, w.Code)
+	assert.Contains(t, w.Body.String(), "func New() *Engine {")
+	assert.Equal(t, `attachment; filename*=UTF-8''`+url.QueryEscape(newFilename), w.Header().Get("Content-Disposition"))
+}
+
 // TestContextRenderYAML tests that the response is serialized as YAML
 // and Content-Type is set to application/x-yaml
 func TestContextRenderYAML(t *testing.T) {

utils.go

@@ -12,6 +12,7 @@ import (
 	"reflect"
 	"runtime"
 	"strings"
+	"unicode"
 )
 
 // BindKey indicates a default bind key.
@@ -151,3 +152,13 @@ func resolveAddress(addr []string) string {
 		panic("too many parameters")
 	}
 }
+
+// https://stackoverflow.com/questions/53069040/checking-a-string-contains-only-ascii-characters
+func isASCII(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] > unicode.MaxASCII {
+			return false
+		}
+	}
+	return true
+}

utils_test.go

@@ -143,3 +143,8 @@ func TestMarshalXMLforH(t *testing.T) {
 	e := h.MarshalXML(enc, x)
 	assert.Error(t, e)
 }
+
+func TestIsASCII(t *testing.T) {
+	assert.Equal(t, isASCII("test"), true)
+	assert.Equal(t, isASCII("🧡💛💚💙💜"), false)
+}