From a6b7585eae06ebb7f4f63db774d871ef9a012744 Mon Sep 17 00:00:00 2001
From: Shirong Lu <73147033+happysnaker@users.noreply.github.com>
Date: Fri, 3 Jul 2026 17:47:21 +0800
Subject: [PATCH] fix: allow empty string to reset StringToString flag

Currently, passing an empty string to a StringToString flag returns
an error. This makes it impossible to override a non-empty default
map with an empty one.

This change allows an empty string value to reset the flag to an
empty map.

Fixes #312
---
 string_to_string.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/string_to_string.go b/string_to_string.go
index 518e1366..c2c6eef2 100644
--- a/string_to_string.go
+++ b/string_to_string.go
@@ -24,6 +24,14 @@ func newStringToStringValue(val map[string]string, p *map[string]string) *string
 // Set updates the flag value from the given string, adding additional mappings or updating existing ones.
 func (s *stringToStringValue) Set(val string) error {
 	var ss []string
+	// Allow empty string to reset the map to empty
+	if val == "" {
+		for k := range *s.value {
+			delete(*s.value, k)
+		}
+		s.changed = true
+		return nil
+	}
 	n := strings.Count(val, "=")
 	switch n {
 	case 0: