fix(grpc-transcode): correctly serialize empty repeated fields to []

apisix/plugins/grpc-transcode/response.lua

@@ -23,6 +23,46 @@ local string = string
 local ngx_decode_base64 = ngx.decode_base64
 local ipairs = ipairs
 local pcall  = pcall
+local type          = type
+local pairs         = pairs
+local setmetatable  = setmetatable
+
+pb.option "decode_default_array"
+-- Protobuf repeated field label value
+local PROTOBUF_REPEATED_LABEL = 3
+local repeated_label = PROTOBUF_REPEATED_LABEL
+
+local function fetch_proto_array_names(proto_obj)
+    local names = {}
+    if type(proto_obj) == "table" then
+        for k,v in pairs(proto_obj) do
+            if type(v) == "table" then
+                local sub_names = fetch_proto_array_names(v)
+                for sub_name,_ in pairs(sub_names) do
+                    names[sub_name] = 1
+                end
+            end
+        end
+        if proto_obj["label"] == repeated_label then
+            names[proto_obj["name"]] = 1
+        end
+    end
+    return names
+end
+
+local function set_default_array(tab, array_names)
+    if type(tab) ~= "table" then
+        return
+    end
+    for k, v in pairs(tab) do
+        if type(v) == "table" then
+            if array_names[k] == 1 then
+                setmetatable(v, core.json.array_mt)
+            end
+            set_default_array(v, array_names)
+        end
+    end
+end
 
 
 local function handle_error_response(status_detail_type, proto)
@@ -132,6 +172,9 @@ return function(ctx, proto, service, method, pb_option, show_status_in_body, sta
         return err_msg
     end
 
+    local array_names = fetch_proto_array_names(proto)
+    set_default_array(decoded, array_names)
+
     local response, err = core.json.encode(decoded)
     if not response then
         err_msg = "failed to json_encode response body"

t/plugin/grpc-transcode4.t

@@ -0,0 +1,154 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+use t::APISIX 'no_plan';
+# ensure that the JSON module of Perl is installed in your test environment.
+# If it is not installed, sudo cpanm JSON.
+use JSON;
+
+no_long_string();
+no_shuffle();
+no_root_location();
+
+add_block_preprocessor(sub {
+    my ($block) = @_;
+
+    if (!$block->request) {
+        $block->set_value("request", "GET /t");
+    }
+});
+
+run_tests;
+
+__DATA__
+
+=== TEST 1: set rule
+--- config
+    location /t {
+       content_by_lua_block {
+          local http = require "resty.http"
+          local t = require("lib.test_admin").test
+          local code, body = t('/apisix/admin/protos/1',
+                ngx.HTTP_PUT,
+                [[{
+                   "content" : "syntax = \"proto3\";
+                    package user;
+                    service UserService {
+                        rpc GetUserInfo(UserRequest) returns (UserResponse) {}
+                     }
+
+                    enum Gender {
+                        GENDER_UNSPECIFIED = 0;
+                        GENDER_MALE = 1;
+                        GENDER_FEMALE = 2;
+                    }
+                    message Job {
+                        string items = 1;
+                    }
+                    message UserRequest {
+                        string name = 1;
+                        int32 age = 2;
+                    }
+
+                    message UserResponse {
+                        Gender gender = 1;
+                        repeated string items = 2;
+                        string message = 3;
+                        Job job = 4;
+                    }"
+                }]]
+              )
+
+             if code >= 300 then
+                 ngx.say(body)
+                 return
+              end
+
+             local code, body = t('/apisix/admin/routes/1',
+                ngx.HTTP_PUT,
+                [[{
+                   "methods": ["POST"],
+                    "uri": "/grpctest",
+                    "plugins": {
+                        "grpc-transcode": {
+                            "proto_id": "1",
+                            "service": "user.UserService",
+                            "method": "GetUserInfo"
+                       }
+                    },
+                    "upstream": {
+                        "scheme": "grpc",
+                            "type": "roundrobin",
+                            "nodes": {
+                            "127.0.0.1:50051": 1
+                        }
+                    }
+                }]]
+             )
+
+            if code >= 300 then
+                ngx.say(body)
+                return
+            end
+            ngx.say(body)
+        }
+    }
+--- response_body
+passed
+
+
+
+=== TEST 2: hit route
+--- request
+POST /grpctest
+{"name":"testUser0","age":0}
+--- more_headers
+Content-Type: application/json
+--- response_body_json
+{"gender":"GENDER_MALE","message":"You are an experienced user!","items":["Senior member","Exclusive service"],"job":{"items":"Intern engineer"}}
+
+
+
+=== TEST 3: hit route
+--- request
+POST /grpctest
+{"name":"testUser1","age":1}
+--- more_headers
+Content-Type: application/json
+--- response_body_json
+{"gender":"GENDER_FEMALE","message":"Welcome new users!","job":{"items":"junior engineer"},"items":[]}
+
+
+
+=== TEST 4: hit route
+--- request
+POST /grpctest
+{"name":"testUser2","age":2}
+--- more_headers
+Content-Type: application/json
+--- response_body_json
+{"items":[],"message":"You are an experienced user!","job":{"items":"senior engineer"},"gender":"GENDER_UNSPECIFIED"}
+
+
+
+=== TEST 5: hit route
+--- request
+POST /grpctest
+{"name":"testUserDefault","age":100}
+--- more_headers
+Content-Type: application/json
+--- response_body_json
+{"gender":"GENDER_UNSPECIFIED","items":[],"message":""}