fix(frame): fix empty topic check error

apps/emqx/src/emqx_frame.erl

@@ -301,7 +301,7 @@ parse_packet(
     Bin,
     #{strict_mode := StrictMode, version := Ver}
 ) ->
-    {TopicName, Rest} = parse_topic_name(Bin, StrictMode),
+    {TopicName, Rest} = parse_utf8_string(Bin, StrictMode),
     {PacketId, Rest1} =
         case QoS of
             ?QOS_0 -> {undefined, Rest};
@@ -310,6 +310,7 @@ parse_packet(
     (PacketId =/= undefined) andalso
         StrictMode andalso validate_packet_id(PacketId),
     {Properties, Payload} = parse_properties(Rest1, Ver, StrictMode),
+    ok = ensure_topic_name_valid(StrictMode, TopicName, Properties),
     Publish = #mqtt_packet_publish{
         topic_name = TopicName,
         packet_id = PacketId,
@@ -422,8 +423,9 @@ parse_will_message(
     StrictMode
 ) ->
     {Props, Rest} = parse_properties(Bin, Ver, StrictMode),
-    {Topic, Rest1} = parse_topic_name(Rest, StrictMode),
+    {Topic, Rest1} = parse_utf8_string(Rest, StrictMode),
     {Payload, Rest2} = parse_binary_data(Rest1),
+    ok = ensure_topic_name_valid(StrictMode, Topic, Props),
     {
         Packet#mqtt_packet_connect{
             will_props = Props,
@@ -621,13 +623,14 @@ parse_binary_data(Bin) when
 ->
     ?PARSE_ERR(malformed_binary_data_length).
 
-parse_topic_name(Bin, false) ->
-    parse_utf8_string(Bin, false);
-parse_topic_name(Bin, true) ->
-    case parse_utf8_string(Bin, true) of
-        {<<>>, _Rest} -> ?PARSE_ERR(empty_topic_name);
-        Result -> Result
-    end.
+ensure_topic_name_valid(false, _TopicName, _Properties) ->
+    ok;
+ensure_topic_name_valid(true, TopicName, _Properties) when TopicName =/= <<>> ->
+    ok;
+ensure_topic_name_valid(true, <<>>, #{'Topic-Alias' := _}) ->
+    ok;
+ensure_topic_name_valid(true, <<>>, _) ->
+    error(empty_topic_name).
 
 %%--------------------------------------------------------------------
 %% Serialize MQTT Packet

apps/emqx/test/emqx_frame_SUITE.erl

@@ -158,12 +158,15 @@ t_parse_malformed_utf8_string(_) ->
     ?ASSERT_FRAME_THROW(utf8_string_invalid, emqx_frame:parse(MalformedPacket, ParseState)).
 
 t_parse_empty_topic_name(_) ->
-    Packet = <<48, 4, 0, 0, 0, 1>>,
-    NormalState = emqx_frame:initial_parse_state(#{strict_mode => false}),
-    ?assertMatch({_, _}, emqx_frame:parse(Packet, NormalState)),
+    Packet = ?PUBLISH_PACKET(?QOS_1, <<>>, 1, #{}, <<>>),
+    ?assertEqual(Packet, parse_serialize(Packet, #{strict_mode => false})),
+    ?ASSERT_FRAME_THROW(empty_topic_name, parse_serialize(Packet, #{strict_mode => true})).
 
-    StrictState = emqx_frame:initial_parse_state(#{strict_mode => true}),
-    ?ASSERT_FRAME_THROW(empty_topic_name, emqx_frame:parse(Packet, StrictState)).
+t_parse_empty_topic_name_with_alias(_) ->
+    Props = #{'Topic-Alias' => 16#AB},
+    Packet = ?PUBLISH_PACKET(?QOS_1, <<>>, 1, Props, <<>>),
+    ?assertEqual(Packet, parse_serialize(Packet, #{strict_mode => false})),
+    ?assertEqual(Packet, parse_serialize(Packet, #{strict_mode => true})).
 
 t_serialize_parse_v3_connect(_) ->
     Bin =