From 5b1ed76a44e30ec8373bf573acf24cb138e271ad Mon Sep 17 00:00:00 2001
From: JianBo He <heeejianbo@gmail.com>
Date: Fri, 17 Dec 2021 16:58:58 +0800
Subject: [PATCH] chore(gw-frame): export types for dialyzer check

---
 apps/emqx_gateway/src/bhvrs/emqx_gateway_frame.erl | 6 ++++++
 apps/emqx_gateway/src/coap/emqx_coap_channel.erl   | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/apps/emqx_gateway/src/bhvrs/emqx_gateway_frame.erl b/apps/emqx_gateway/src/bhvrs/emqx_gateway_frame.erl
index 87410f7d8..5d3b81d54 100644
--- a/apps/emqx_gateway/src/bhvrs/emqx_gateway_frame.erl
+++ b/apps/emqx_gateway/src/bhvrs/emqx_gateway_frame.erl
@@ -32,6 +32,12 @@
 
 -type serialize_options() :: map().
 
+-export_type([ parse_state/0
+             , parse_result/0
+             , serialize_options/0
+             , frame/0
+             ]).
+
 %% Callbacks
 
 %% @doc Initial the frame parser states
diff --git a/apps/emqx_gateway/src/coap/emqx_coap_channel.erl b/apps/emqx_gateway/src/coap/emqx_coap_channel.erl
index 9b1e5821c..ab079b587 100644
--- a/apps/emqx_gateway/src/coap/emqx_coap_channel.erl
+++ b/apps/emqx_gateway/src/coap/emqx_coap_channel.erl
@@ -235,7 +235,7 @@ handle_call({subscribe, Topic, SubOpts}, _From,
                          session = Session}) ->
     Token = maps:get(token,
                      maps:get(sub_props, SubOpts, #{}),
-                     undefined),
+                     <<>>),
     NSubOpts = maps:merge(
                  emqx_gateway_utils:default_subopts(),
                  SubOpts),