fix(gin): keep encoded slashes in trailing slash redirects

gin.go

@@ -9,6 +9,7 @@ import (
 	"html/template"
 	"net"
 	"net/http"
+	"net/url"
 	"os"
 	"path"
 	"strings"
@@ -810,16 +811,28 @@ func serveError(c *Context, code int, defaultMessage []byte) {
 func redirectTrailingSlash(c *Context) {
 	req := c.Request
 	p := req.URL.Path
+	// Routing matched the escaped path, so build the redirect from it too;
+	// otherwise an encoded slash (%2F) would turn into a real path separator.
+	escaped := c.engine.UseEscapedPath || (c.engine.UseRawPath && req.URL.RawPath != "")
+	if escaped {
+		p = req.URL.EscapedPath()
+	}
 	if prefix := path.Clean(c.Request.Header.Get("X-Forwarded-Prefix")); prefix != "." {
 		prefix = sanitizePathChars(prefix)
 		prefix = removeRepeatedChar(prefix, '/')
 
-		p = prefix + "/" + req.URL.Path
+		p = prefix + "/" + p
 	}
 	req.URL.Path = p + "/"
 	if length := len(p); length > 1 && p[length-1] == '/' {
 		req.URL.Path = p[:length-1]
 	}
+	if escaped {
+		if unescaped, err := url.PathUnescape(req.URL.Path); err == nil {
+			req.URL.RawPath = req.URL.Path
+			req.URL.Path = unescaped
+		}
+	}
 	redirectRequest(c)
 }
 

routes_test.go

@@ -303,6 +303,24 @@ func TestRouteRedirectTrailingSlash(t *testing.T) {
 	assert.Equal(t, http.StatusNotFound, w.Code)
 }
 
+func TestRouteRedirectTrailingSlashKeepsEscapedPath(t *testing.T) {
+	for _, useEscapedPath := range []bool{false, true} {
+		router := New()
+		router.UseRawPath = !useEscapedPath
+		router.UseEscapedPath = useEscapedPath
+		router.GET("/files/:name", func(c *Context) {})
+		router.GET("/dirs/:name/", func(c *Context) {})
+
+		w := PerformRequest(router, http.MethodGet, "/files/a%2Fb/")
+		assert.Equal(t, http.StatusMovedPermanently, w.Code)
+		assert.Equal(t, "/files/a%2Fb", w.Header().Get("Location"))
+
+		w = PerformRequest(router, http.MethodGet, "/dirs/a%2Fb")
+		assert.Equal(t, http.StatusMovedPermanently, w.Code)
+		assert.Equal(t, "/dirs/a%2Fb/", w.Header().Get("Location"))
+	}
+}
+
 func TestRouteRedirectFixedPath(t *testing.T) {
 	router := New()
 	router.RedirectFixedPath = true