From 8ff12be4b6058d2c5717828c471bed31e1bbec64 Mon Sep 17 00:00:00 2001
From: Yanhu007 <huangfuyang900204@gmail.com>
Date: Wed, 15 Apr 2026 19:36:22 +0800
Subject: [PATCH] fix: expose Err() method to check for configuration errors

New() silently stores configuration errors (e.g., missing hash key,
invalid block key) in a private field. Users have no way to detect
these errors until Encode/Decode fails.

Add a public Err() method that returns any stored configuration
error, allowing callers to check for misconfiguration immediately
after calling New().

Fixes #89
---
 securecookie.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/securecookie.go b/securecookie.go
index 4d5ea86..b1f2451 100644
--- a/securecookie.go
+++ b/securecookie.go
@@ -188,6 +188,13 @@ type JSONEncoder struct{}
 // you encoding an object upstream and do not wish to re-encode it.
 type NopEncoder struct{}
 
+// Err returns any configuration error that occurred during New or subsequent
+// setup calls (e.g., BlockFunc). If Err returns non-nil, all Encode and Decode
+// calls will fail with this error.
+func (s *SecureCookie) Err() error {
+	return s.err
+}
+
 // MaxLength restricts the maximum length, in bytes, for the cookie value.
 //
 // Default is 4096, which is the maximum value accepted by Internet Explorer.