From c01ac072c63dc70f30476853a938795e8bf102c2 Mon Sep 17 00:00:00 2001
From: Shirong Lu <73147033+happysnaker@users.noreply.github.com>
Date: Fri, 3 Jul 2026 16:44:11 +0800
Subject: [PATCH] fix: handle String() round-trip in Set() for stringToString

String() wraps the output in [...], but Set() was not stripping
those brackets before parsing. This caused round-trip failures
when the output of String() (e.g. [x=[]]) was passed back to Set(),
resulting in keys like '[x' instead of 'x'.

Fixes #413
---
 string_to_string.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/string_to_string.go b/string_to_string.go
index 518e1366..24ecee18 100644
--- a/string_to_string.go
+++ b/string_to_string.go
@@ -24,6 +24,10 @@ 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
+	// Support round-trip from String() output, which wraps the value in [...]
+	if strings.HasPrefix(val, "[") && strings.HasSuffix(val, "]") {
+		val = val[1 : len(val)-1]
+	}
 	n := strings.Count(val, "=")
 	switch n {
 	case 0: