From 4885da9e5e593ecb62cf1b42a00635006fa05c95 Mon Sep 17 00:00:00 2001
From: Yixin Guo <yixin.guo@securityscorecard.io>
Date: Wed, 6 Aug 2025 13:59:58 -0500
Subject: [PATCH] fix(grpc): Fix error "proto3 disallow 'optional' label"

    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.
---
 .../unreleased/kong/fix-missing-grpc-optional-support.yml      | 3 +++
 kong/tools/grpc.lua                                            | 1 +
 spec/fixtures/grpc/targetservice.proto                         | 2 +-
 3 files changed, 5 insertions(+), 1 deletion(-)
 create mode 100644 changelog/unreleased/kong/fix-missing-grpc-optional-support.yml

diff --git a/changelog/unreleased/kong/fix-missing-grpc-optional-support.yml b/changelog/unreleased/kong/fix-missing-grpc-optional-support.yml
new file mode 100644
index 00000000000..f0f43e80f6d
--- /dev/null
+++ 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
\ No newline at end of file
diff --git a/kong/tools/grpc.lua b/kong/tools/grpc.lua
index a7d62f01b8f..31b0bb6ab69 100644
--- 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
index e2f887fecce..59941114841 100644
--- 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 {