From 2d10d6971df821a5188d5604cf9fa47707bf5abe Mon Sep 17 00:00:00 2001
From: Gilbert Wong <gilbertwong96@icloud.com>
Date: Sat, 8 Sep 2018 12:01:22 +0800
Subject: [PATCH] add pattern match for topic alias Prior to this change, it
 assume that topic_alias exists defaultly which may cause the unexpected bug

This change fix this bug above
---
 src/emqx_protocol.erl | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/emqx_protocol.erl b/src/emqx_protocol.erl
index 4602337eb..1dae228d7 100644
--- a/src/emqx_protocol.erl
+++ b/src/emqx_protocol.erl
@@ -650,9 +650,15 @@ check_publish(Packet, PState) ->
 check_pub_caps(#mqtt_packet{header = #mqtt_packet_header{qos = QoS, retain = Retain},
                             variable = #mqtt_packet_publish{ properties = Properties}},
                #pstate{zone = Zone}) ->
-    #{'Topic-Alias' := TopicAlias} = Properties,
+    emqx_mqtt_caps:check_pub(Zone, #{qos => QoS, retain => Retain});
+check_pub_caps(#mqtt_packet{header = #mqtt_packet_header{qos = QoS, retain = Retain},
+                            variable = #mqtt_packet_publish{
+                                          properties = #{'Topic-Alias' := TopicAlias}
+                                         }},
+               #pstate{zone = Zone}) ->
     emqx_mqtt_caps:check_pub(Zone, #{qos => QoS, retain => Retain, topic_alias => TopicAlias}).
 
+
 check_pub_acl(_Packet, #pstate{is_super = IsSuper, enable_acl = EnableAcl})
     when IsSuper orelse (not EnableAcl) ->
     ok;