fix(grpc): Fix error "proto3 disallow 'optional' label"

yixinguo-ssc · yixinguo-ssc · commit 4885da9e5e59 · 2025-08-06T13:59:58.000-05:00
When grpc-gateway plugin loads a proto3 proto file with optional labeled fields, it will throw an error "proto3 disallow 'optional' label". This fixes the issue by enabling proto3_optional in protoc.
diff --git a/changelog/unreleased/kong/fix-missing-grpc-optional-support.yml b/changelog/unreleased/kong/fix-missing-grpc-optional-support.yml
@@ -0,0 +1,3 @@
+message: Fixed an issue where gRPC plugins lack support for "optional".
+scope: Plugin
+type: bugfix
diff --git a/kong/tools/grpc.lua b/kong/tools/grpc.lua
@@ -77,6 +77,7 @@ function _M.new()
     protoc_instance:addpath(v)
   end
   protoc_instance.include_imports = true
+  protoc_instance.proto3_optional = true
 
   return setmetatable({
     protoc_instance = protoc_instance,
diff --git a/spec/fixtures/grpc/targetservice.proto b/spec/fixtures/grpc/targetservice.proto
@@ -56,7 +56,7 @@ service Bouncer {
 
 message HelloRequest {
   string greeting = 1;
-  bool boolean_test = 2;
+  optional bool boolean_test = 2;
 }
 
 message HelloResponse {

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+message: Fixed an issue where gRPC plugins lack support for "optional".`
	`2`	`+scope: Plugin`
	`3`	`+type: bugfix`
Original file line number	Diff line number	Diff line change
`@@ -56,7 +56,7 @@ service Bouncer {`
`56`	`56`
`57`	`57`	`message HelloRequest {`
`58`	`58`	`string greeting = 1;`
`59`		`- bool boolean_test = 2;`
	`59`	`+ optional bool boolean_test = 2;`
`60`	`60`	`}`
`61`	`61`
`62`	`62`	`message HelloResponse {`