From d2395fb43a5f4fcf2146deca2519f45c133f999f Mon Sep 17 00:00:00 2001
From: eWloYW8 <3171132517@qq.com>
Date: Sun, 24 Aug 2025 13:16:30 +0800
Subject: [PATCH] fix: allow disabling ALPN by setting an empty array (#2225)

---
 adapter/outbound/hysteria.go  | 2 +-
 adapter/outbound/hysteria2.go | 2 +-
 adapter/outbound/trojan.go    | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/adapter/outbound/hysteria.go b/adapter/outbound/hysteria.go
index 966fa745..38318459 100644
--- a/adapter/outbound/hysteria.go
+++ b/adapter/outbound/hysteria.go
@@ -172,7 +172,7 @@ func NewHysteria(option HysteriaOption) (*Hysteria, error) {
 		return nil, err
 	}
 
-	if len(option.ALPN) > 0 {
+	if option.ALPN != nil { // structure's Decode will ensure value not nil when input has value even it was set an empty array
 		tlsConfig.NextProtos = option.ALPN
 	} else {
 		tlsConfig.NextProtos = []string{DefaultALPN}
diff --git a/adapter/outbound/hysteria2.go b/adapter/outbound/hysteria2.go
index cb844e1f..e7b9f0b5 100644
--- a/adapter/outbound/hysteria2.go
+++ b/adapter/outbound/hysteria2.go
@@ -153,7 +153,7 @@ func NewHysteria2(option Hysteria2Option) (*Hysteria2, error) {
 		return nil, err
 	}
 
-	if len(option.ALPN) > 0 {
+	if option.ALPN != nil { // structure's Decode will ensure value not nil when input has value even it was set an empty array
 		tlsConfig.NextProtos = option.ALPN
 	}
 
diff --git a/adapter/outbound/trojan.go b/adapter/outbound/trojan.go
index 9795ed78..f33ac5d6 100644
--- a/adapter/outbound/trojan.go
+++ b/adapter/outbound/trojan.go
@@ -95,7 +95,7 @@ func (t *Trojan) StreamConnContext(ctx context.Context, c net.Conn, metadata *C.
 		}
 
 		alpn := trojan.DefaultWebsocketALPN
-		if len(t.option.ALPN) != 0 {
+		if t.option.ALPN != nil { // structure's Decode will ensure value not nil when input has value even it was set an empty array
 			alpn = t.option.ALPN
 		}
 
@@ -119,7 +119,7 @@ func (t *Trojan) StreamConnContext(ctx context.Context, c net.Conn, metadata *C.
 		// default tcp network
 		// handle TLS
 		alpn := trojan.DefaultALPN
-		if len(t.option.ALPN) != 0 {
+		if t.option.ALPN != nil { // structure's Decode will ensure value not nil when input has value even it was set an empty array
 			alpn = t.option.ALPN
 		}
 		c, err = vmess.StreamTLSConn(ctx, c, &vmess.TLSConfig{