fix(gcp_pubsub_consumer): fabricate topic mapping when producing v1 config

Fixes https://emqx.atlassian.net/browse/EMQX-11891

apps/emqx_bridge/test/emqx_bridge_v2_testlib.erl

@@ -692,7 +692,6 @@ t_consume(Config, Opts) ->
                 )
             ),
             ok = add_source_hookpoint(Config),
-            ResourceId = resource_id(Config),
             ?retry(
                 _Sleep = 200,
                 _Attempts = 20,
@@ -732,6 +731,13 @@ t_create_via_http(Config) ->
                     Config
                 )
             ),
+
+            %% check that v1 list API is fine
+            ?assertMatch(
+                {ok, {{_, 200, _}, _, _}},
+                list_bridges_http_api_v1()
+            ),
+
             ok
         end,
         []

apps/emqx_bridge_gcp_pubsub/src/emqx_bridge_gcp_pubsub_consumer_action_info.erl

@@ -60,8 +60,9 @@ connector_action_config_to_bridge_v1_config(ConnectorConfig, SourceConfig) ->
             fun(RO) -> maps:with(bridge_v1_resource_opts_fields(), RO) end,
             BridgeV1Config2
         ),
-    BridgeV1Config4 = emqx_utils_maps:deep_remove([<<"parameters">>, <<"topic">>], BridgeV1Config3),
-    emqx_utils_maps:rename(<<"parameters">>, <<"consumer">>, BridgeV1Config4).
+    BridgeV1Config4 = maybe_fabricate_topic_mapping(BridgeV1Config3),
+    BridgeV1Config = emqx_utils_maps:deep_remove([<<"parameters">>, <<"topic">>], BridgeV1Config4),
+    emqx_utils_maps:rename(<<"parameters">>, <<"consumer">>, BridgeV1Config).
 
 %%------------------------------------------------------------------------------------------
 %% Internal helper fns
@@ -74,6 +75,23 @@ maybe_set_pubsub_topic(#{<<"topic_mapping">> := [#{<<"pubsub_topic">> := Topic}
 maybe_set_pubsub_topic(Params) ->
     Params.
 
+%% The old schema requires `topic_mapping', which is now hidden.
+maybe_fabricate_topic_mapping(#{<<"parameters">> := Params0} = BridgeV1Config0) ->
+    #{<<"topic">> := Topic} = Params0,
+    case maps:get(<<"topic_mapping">>, Params0, undefined) of
+        [_ | _] ->
+            BridgeV1Config0;
+        _ ->
+            %% Have to fabricate an MQTT topic, unfortunately...  QoS and payload already
+            %% have defaults.
+            FakeTopicMapping = #{
+                <<"pubsub_topic">> => Topic,
+                <<"mqtt_topic">> => <<>>
+            },
+            Params = Params0#{<<"topic_mapping">> => [FakeTopicMapping]},
+            BridgeV1Config0#{<<"parameters">> := Params}
+    end.
+
 resource_opts_fields() ->
     [
         to_bin(K)

apps/emqx_bridge_gcp_pubsub/src/emqx_bridge_gcp_pubsub_consumer_worker.erl

@@ -783,7 +783,7 @@ legacy_maybe_publish_mqtt_message(
     },
     SourceResId,
     FullMessage
-) ->
+) when MQTTTopic =/= <<>> ->
     Payload = render(FullMessage, PayloadTemplate),
     MQTTMessage = emqx_message:make(SourceResId, MQTTQoS, MQTTTopic, Payload),
     _ = emqx:publish(MQTTMessage),

apps/emqx_bridge_gcp_pubsub/test/emqx_bridge_v2_gcp_pubsub_consumer_SUITE.erl

@@ -35,7 +35,8 @@ common_init_per_testcase(TestCase, Config0) ->
     ServiceAccountJSON =
         #{<<"project_id">> := ProjectId} =
         emqx_bridge_gcp_pubsub_utils:generate_service_account_json(),
-    Name = atom_to_binary(TestCase),
+    UniqueNum = integer_to_binary(erlang:unique_integer()),
+    Name = <<(atom_to_binary(TestCase))/binary, UniqueNum/binary>>,
     ConnectorConfig = connector_config(Name, ServiceAccountJSON),
     PubsubTopic = Name,
     SourceConfig = source_config(#{
@@ -117,6 +118,10 @@ t_start_stop(Config) ->
     ok = emqx_bridge_v2_testlib:t_start_stop(Config, gcp_pubsub_stop),
     ok.
 
+t_create_via_http(Config) ->
+    ok = emqx_bridge_v2_testlib:t_create_via_http(Config),
+    ok.
+
 t_consume(Config) ->
     Topic = ?config(pubsub_topic, Config),
     Payload = #{<<"key">> => <<"value">>},