From aa7741f8b86365f8251ac99472857e16fee8276a Mon Sep 17 00:00:00 2001
From: bytelazy <82265836+bytelazy@users.noreply.github.com>
Date: Sat, 4 Oct 2025 17:28:12 +0800
Subject: [PATCH 1/2] test: cover grpc-transcode empty array responses

---
 apisix/plugins/grpc-transcode/response.lua | 45 +++++++++++++++++++
 t/plugin/grpc-transcode.t                  | 51 ++++++++++++++++++++++
 2 files changed, 96 insertions(+)

diff --git a/apisix/plugins/grpc-transcode/response.lua b/apisix/plugins/grpc-transcode/response.lua
index 9dd6780f049d..2487409a5e96 100644
--- a/apisix/plugins/grpc-transcode/response.lua
+++ b/apisix/plugins/grpc-transcode/response.lua
@@ -23,6 +23,48 @@ 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
+            if proto_obj["name"] then
+                names[proto_obj["name"]] = 1
+            end
+        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 +174,9 @@ 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"
diff --git a/t/plugin/grpc-transcode.t b/t/plugin/grpc-transcode.t
index e261bf7bd554..c7c4d0d71ef6 100644
--- a/t/plugin/grpc-transcode.t
+++ b/t/plugin/grpc-transcode.t
@@ -761,3 +761,54 @@ POST /grpctest
 Content-Type: application/json
 --- response_body eval
 qr/"gender":2/
+
+
+
+=== TEST 30: set route (return empty array from grpc server)
+--- config
+    location /t {
+        content_by_lua_block {
+            local t = require("lib.test_admin").test
+            local code, body = t('/apisix/admin/routes/1',
+                ngx.HTTP_PUT,
+                [[{
+                    "methods": ["GET", "POST"],
+                    "uri": "/grpctest",
+                    "plugins": {
+                        "grpc-transcode": {
+                            "proto_id": "1",
+                            "service": "helloworld.Greeter",
+                            "method": "SayHello"
+                        }
+                    },
+                    "upstream": {
+                        "scheme": "grpc",
+                        "type": "roundrobin",
+                        "nodes": {
+                            "127.0.0.1:10051": 1
+                        }
+                    }
+                }]]
+            )
+
+            if code >= 300 then
+                ngx.status = code
+            end
+            ngx.say(body)
+        }
+    }
+--- request
+GET /t
+--- response_body
+passed
+
+
+
+=== TEST 31: hit route, response keeps empty array
+--- request
+POST /grpctest
+{"name":"world","items":[]}
+--- more_headers
+Content-Type: application/json
+--- response_body eval
+qr/"items":\[\]/

From 6aac6c57a79a528ca2acf59317c966e54169ce50 Mon Sep 17 00:00:00 2001
From: bytelazy <82265836+bytelazy@users.noreply.github.com>
Date: Sun, 12 Oct 2025 16:04:14 +0000
Subject: [PATCH 2/2] remove option: decode_default_array

---
 apisix/plugins/grpc-transcode/response.lua | 1 -
 1 file changed, 1 deletion(-)

diff --git a/apisix/plugins/grpc-transcode/response.lua b/apisix/plugins/grpc-transcode/response.lua
index 2487409a5e96..ae3f7a6ddacf 100644
--- a/apisix/plugins/grpc-transcode/response.lua
+++ b/apisix/plugins/grpc-transcode/response.lua
@@ -27,7 +27,6 @@ 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