From 1864aa316c5417407e8543975af5eda62afaab74 Mon Sep 17 00:00:00 2001
From: Gorka Lerchundi Osa <glertxundi@gmail.com>
Date: Mon, 23 Nov 2020 00:38:25 +0100
Subject: [PATCH] protoc-gen-{grpc-gateway,openapiv2}: add optional support

Let `protoc` know that these generators support optional keywords. This
is by no means an implementation in `grpc-gateway` of the optional aware
generated code, it's just shielding of being considered as blockers in
code generation workflows.

Closes #1278
---
 .circleci/config.yml                          |   1 +
 Makefile                                      |  29 ++--
 .../internal/clients/abe/api/swagger.yaml     |  31 +++++
 .../abe/api_a_bit_of_everything_service.go    |  20 +++
 .../model_examplepb_a_bit_of_everything.go    |   1 +
 .../proto/examplepb/a_bit_of_everything.pb.go | 124 ++++++++++--------
 .../proto/examplepb/a_bit_of_everything.proto |   3 +
 .../a_bit_of_everything.swagger.json          |  32 +++++
 .../proto/examplepb/stream.swagger.json       |   4 +
 protoc-gen-grpc-gateway/BUILD.bazel           |   1 +
 protoc-gen-grpc-gateway/main.go               |   2 +
 protoc-gen-openapiv2/main.go                  |   3 +-
 12 files changed, 181 insertions(+), 70 deletions(-)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index 1f764bbaeab..a076f81e88f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -9,6 +9,7 @@ commands:
           startup --output_base /root/.cache/_grpc_gateway_bazel
           build --test_output errors
           build --features race
+          build --protocopt=--experimental_allow_proto3_optional # To make proto_library rules include optional support at build time
           # Workaround https://github.com/bazelbuild/bazel/issues/3645
           # See https://docs.bazel.build/versions/0.23.0/command-line-reference.html
           build --local_ram_resources=4096 # Circle Docker runners have 4G of memory
diff --git a/Makefile b/Makefile
index da225ece5a4..5148675ee28 100644
--- a/Makefile
+++ b/Makefile
@@ -154,6 +154,7 @@ GENERATE_UNBOUND_METHODS_EXAMPLE_SRCS=$(EXAMPLE_CLIENT_DIR)/generateunboundmetho
 EXAMPLE_CLIENT_SRCS=$(ECHO_EXAMPLE_SRCS) $(ABE_EXAMPLE_SRCS) $(UNANNOTATED_ECHO_EXAMPLE_SRCS) $(RESPONSE_BODY_EXAMPLE_SRCS) $(GENERATE_UNBOUND_METHODS_EXAMPLE_SRCS)
 SWAGGER_CODEGEN=swagger-codegen
 
+PROTOC=protoc --experimental_allow_proto3_optional
 PROTOC_INC_PATH=$(dir $(shell which protoc))/../include
 
 .SUFFIXES: .go .proto
@@ -165,7 +166,7 @@ $(GO_GRPC_PLUGIN):
 	go build -o $(GO_GRPC_PLUGIN) $(GO_GRPC_PLUGIN_PKG)
 
 $(OPENAPIV2_GO): $(OPENAPIV2_PROTO) $(GO_PLUGIN)
-	protoc -I $(PROTOC_INC_PATH) --plugin=$(GO_PLUGIN) -I. --go_out=paths=source_relative:. $(OPENAPIV2_PROTO)
+	$(PROTOC) -I $(PROTOC_INC_PATH) --plugin=$(GO_PLUGIN) -I. --go_out=paths=source_relative:. $(OPENAPIV2_PROTO)
 
 $(GATEWAY_PLUGIN): $(GATEWAY_PLUGIN_SRC) $(OPENAPIV2_GO)
 	go build -o $@ $(GATEWAY_PLUGIN_PKG)
@@ -174,44 +175,44 @@ $(OPENAPI_PLUGIN): $(OPENAPI_PLUGIN_SRC) $(OPENAPIV2_GO)
 	go build -o $@ $(OPENAPI_PLUGIN_PKG)
 
 $(EXAMPLE_SVCSRCS): $(GO_PLUGIN) $(GO_GRPC_PLUGIN) $(EXAMPLES)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(EXAMPLES)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(EXAMPLES)
 $(EXAMPLE_DEPSRCS): $(GO_PLUGIN) $(GO_GRPC_PLUGIN) $(EXAMPLE_DEPS)
-	protoc -I $(PROTOC_INC_PATH) -I. --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(@:.pb.go=.proto)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(@:.pb.go=.proto)
 
 $(RUNTIME_TEST_SRCS): $(GO_PLUGIN) $(GO_GRPC_PLUGIN) $(RUNTIME_TEST_PROTO)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(RUNTIME_TEST_PROTO)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(RUNTIME_TEST_PROTO)
 
 $(APICONFIG_SRCS): $(GO_PLUGIN) $(APICONFIG_PROTO)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --go_out=paths=source_relative:. $(APICONFIG_PROTO)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --go_out=paths=source_relative:. $(APICONFIG_PROTO)
 
 $(EXAMPLE_GWSRCS): ADDITIONAL_GW_FLAGS:=$(ADDITIONAL_GW_FLAGS),grpc_api_configuration=examples/internal/proto/examplepb/unannotated_echo_service.yaml
 $(EXAMPLE_GWSRCS): ADDITIONAL_SA_FLAGS:=,standalone=true,grpc_api_configuration=examples/internal/proto/examplepb/standalone_echo_service.yaml
 $(EXAMPLE_GWSRCS): $(GATEWAY_PLUGIN) $(EXAMPLES)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,allow_repeated_fields_in_body=true,paths=source_relative$(ADDITIONAL_SA_FLAGS):. $(STANDALONE_EXAMPLES)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,allow_repeated_fields_in_body=true,paths=source_relative$(ADDITIONAL_SA_FLAGS):. $(STANDALONE_EXAMPLES)
 	mv examples/internal/proto/examplepb/unannotated_echo_service.pb.gw.go examples/internal/proto/standalone/
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,allow_repeated_fields_in_body=true,paths=source_relative$(ADDITIONAL_GW_FLAGS):. $(EXAMPLES)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,allow_repeated_fields_in_body=true,paths=source_relative$(ADDITIONAL_GW_FLAGS):. $(EXAMPLES)
 
 
 $(EXAMPLE_OPENAPISRCS): ADDITIONAL_SWG_FLAGS:=$(ADDITIONAL_SWG_FLAGS),grpc_api_configuration=examples/internal/proto/examplepb/unannotated_echo_service.yaml,openapi_configuration=examples/internal/proto/examplepb/unannotated_echo_service.swagger.yaml
 $(EXAMPLE_OPENAPISRCS): $(OPENAPI_PLUGIN) $(OPENAPI_EXAMPLES)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(OPENAPI_PLUGIN) --openapiv2_out=logtostderr=true,allow_repeated_fields_in_body=true,use_go_templates=true$(ADDITIONAL_SWG_FLAGS):. $(OPENAPI_EXAMPLES)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(OPENAPI_PLUGIN) --openapiv2_out=logtostderr=true,allow_repeated_fields_in_body=true,use_go_templates=true$(ADDITIONAL_SWG_FLAGS):. $(OPENAPI_EXAMPLES)
 
 $(EXAMPLE_OPENAPIMERGESRCS): $(OPENAPI_PLUGIN) $(OPENAPIMERGE_EXAMPLES)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(OPENAPI_PLUGIN) --openapiv2_out=logtostderr=true,allow_repeated_fields_in_body=true,use_go_templates=true,allow_merge=true,merge_file_name=$(EXAMPLE_OPENAPIMERGESRCS:.swagger.json=):. $(OPENAPIMERGE_EXAMPLES)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(OPENAPI_PLUGIN) --openapiv2_out=logtostderr=true,allow_repeated_fields_in_body=true,use_go_templates=true,allow_merge=true,merge_file_name=$(EXAMPLE_OPENAPIMERGESRCS:.swagger.json=):. $(OPENAPIMERGE_EXAMPLES)
 
 $(GENERATE_UNBOUND_METHODS_EXAMPLE_GWSRCS): $(GATEWAY_PLUGIN) $(GENERATE_UNBOUND_METHODS_EXAMPLE)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,paths=source_relative,allow_repeated_fields_in_body=true,generate_unbound_methods=true$(ADDITIONAL_GW_FLAGS):. $(GENERATE_UNBOUND_METHODS_EXAMPLE)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,paths=source_relative,allow_repeated_fields_in_body=true,generate_unbound_methods=true$(ADDITIONAL_GW_FLAGS):. $(GENERATE_UNBOUND_METHODS_EXAMPLE)
 $(GENERATE_UNBOUND_METHODS_EXAMPLE_SVCSRCS): $(GO_PLUGIN) $(GENERATE_UNBOUND_METHODS_EXAMPLE)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(GENERATE_UNBOUND_METHODS_EXAMPLE)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(GENERATE_UNBOUND_METHODS_EXAMPLE)
 $(GENERATE_UNBOUND_METHODS_EXAMPLE_OPENAPISRCS): $(OPENAPI_PLUGIN) $(GENERATE_UNBOUND_METHODS_EXAMPLE)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(OPENAPI_PLUGIN) --openapiv2_out=logtostderr=true,allow_repeated_fields_in_body=true,use_go_templates=true,generate_unbound_methods=true:. $(GENERATE_UNBOUND_METHODS_EXAMPLE)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(OPENAPI_PLUGIN) --openapiv2_out=logtostderr=true,allow_repeated_fields_in_body=true,use_go_templates=true,generate_unbound_methods=true:. $(GENERATE_UNBOUND_METHODS_EXAMPLE)
 
 $(HELLOWORLD_SVCSRCS): $(GO_PLUGIN) $(GO_GRPC_PLUGIN) $(HELLOWORLD)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(HELLOWORLD)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GO_PLUGIN) --plugin=$(GO_GRPC_PLUGIN) --go_out=paths=source_relative:. --go-grpc_out=paths=source_relative,require_unimplemented_servers=false:. $(HELLOWORLD)
 
 $(HELLOWORLD_GWSRCS):
 $(HELLOWORLD_GWSRCS): $(GATEWAY_PLUGIN) $(HELLOWORLD)
-	protoc -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,allow_repeated_fields_in_body=true,paths=source_relative$(ADDITIONAL_GW_FLAGS):. $(HELLOWORLD)
+	$(PROTOC) -I $(PROTOC_INC_PATH) -I. -I$(GOOGLEAPIS_DIR) --plugin=$(GATEWAY_PLUGIN) --grpc-gateway_out=logtostderr=true,allow_repeated_fields_in_body=true,paths=source_relative$(ADDITIONAL_GW_FLAGS):. $(HELLOWORLD)
 
 $(ECHO_EXAMPLE_SRCS): $(ECHO_EXAMPLE_SPEC)
 	$(SWAGGER_CODEGEN) generate -i $(ECHO_EXAMPLE_SPEC) \
diff --git a/examples/internal/clients/abe/api/swagger.yaml b/examples/internal/clients/abe/api/swagger.yaml
index ae436d26464..370e5fbac81 100644
--- a/examples/internal/clients/abe/api/swagger.yaml
+++ b/examples/internal/clients/abe/api/swagger.yaml
@@ -386,6 +386,13 @@ paths:
         type: "string"
         x-exportParamName: "OutputOnlyStringViaFieldBehaviorAnnotation"
         x-optionalDataType: "String"
+      - name: "optionlStringValue"
+        in: "query"
+        description: "mark a field as optional."
+        required: false
+        type: "string"
+        x-exportParamName: "OptionlStringValue"
+        x-optionalDataType: "String"
       responses:
         200:
           description: "A successful response."
@@ -693,6 +700,13 @@ paths:
         type: "string"
         x-exportParamName: "OutputOnlyStringViaFieldBehaviorAnnotation"
         x-optionalDataType: "String"
+      - name: "optionlStringValue"
+        in: "query"
+        description: "mark a field as optional."
+        required: false
+        type: "string"
+        x-exportParamName: "OptionlStringValue"
+        x-optionalDataType: "String"
       responses:
         200:
           description: "A successful response."
@@ -987,6 +1001,13 @@ paths:
         type: "string"
         x-exportParamName: "OutputOnlyStringViaFieldBehaviorAnnotation"
         x-optionalDataType: "String"
+      - name: "optionlStringValue"
+        in: "query"
+        description: "mark a field as optional."
+        required: false
+        type: "string"
+        x-exportParamName: "OptionlStringValue"
+        x-optionalDataType: "String"
       responses:
         200:
           description: "A successful response."
@@ -1301,6 +1322,13 @@ paths:
         type: "string"
         x-exportParamName: "OutputOnlyStringViaFieldBehaviorAnnotation"
         x-optionalDataType: "String"
+      - name: "optionlStringValue"
+        in: "query"
+        description: "mark a field as optional."
+        required: false
+        type: "string"
+        x-exportParamName: "OptionlStringValue"
+        x-optionalDataType: "String"
       responses:
         200:
           description: "A successful response."
@@ -2523,6 +2551,9 @@ definitions:
         type: "string"
         title: "mark a field as readonly in Open API definition"
         readOnly: true
+      optionlStringValue:
+        type: "string"
+        title: "mark a field as optional"
     externalDocs:
       description: "Find out more about ABitOfEverything"
       url: "https://github.com/grpc-ecosystem/grpc-gateway"
diff --git a/examples/internal/clients/abe/api_a_bit_of_everything_service.go b/examples/internal/clients/abe/api_a_bit_of_everything_service.go
index 80e0e1453cb..b820aa1f739 100644
--- a/examples/internal/clients/abe/api_a_bit_of_everything_service.go
+++ b/examples/internal/clients/abe/api_a_bit_of_everything_service.go
@@ -211,6 +211,7 @@ ABitOfEverythingServiceApiService
      * @param "NestedAnnotationOk" (optional.String) -  DeepEnum description.   - FALSE: FALSE is false.  - TRUE: TRUE is true.
      * @param "Int64OverrideType" (optional.Int64) - 
      * @param "OutputOnlyStringViaFieldBehaviorAnnotation" (optional.String) -  mark a field as readonly in Open API definition.
+     * @param "OptionlStringValue" (optional.String) -  mark a field as optional.
 
 @return ExamplepbABitOfEverything
 */
@@ -248,6 +249,7 @@ type ABitOfEverythingServiceCheckGetQueryParamsOpts struct {
 	NestedAnnotationOk optional.String
 	Int64OverrideType optional.Int64
 	OutputOnlyStringViaFieldBehaviorAnnotation optional.String
+	OptionlStringValue optional.String
 }
 
 func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceCheckGetQueryParams(ctx context.Context, singleNestedName string, floatValue float32, requiredStringViaFieldBehaviorAnnotation string, localVarOptionals *ABitOfEverythingServiceCheckGetQueryParamsOpts) (ExamplepbABitOfEverything, *http.Response, error) {
@@ -365,6 +367,9 @@ func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceCheckGetQuery
 	if localVarOptionals != nil && localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.IsSet() {
 		localVarQueryParams.Add("outputOnlyStringViaFieldBehaviorAnnotation", parameterToString(localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.Value(), ""))
 	}
+	if localVarOptionals != nil && localVarOptionals.OptionlStringValue.IsSet() {
+		localVarQueryParams.Add("optionlStringValue", parameterToString(localVarOptionals.OptionlStringValue.Value(), ""))
+	}
 	// to determine the Content-Type header
 	localVarHttpContentTypes := []string{"application/json", "application/x-foo-mime"}
 
@@ -525,6 +530,7 @@ ABitOfEverythingServiceApiService
      * @param "NestedAnnotationAmount" (optional.Int64) - 
      * @param "Int64OverrideType" (optional.Int64) - 
      * @param "OutputOnlyStringViaFieldBehaviorAnnotation" (optional.String) -  mark a field as readonly in Open API definition.
+     * @param "OptionlStringValue" (optional.String) -  mark a field as optional.
 
 @return ExamplepbABitOfEverything
 */
@@ -562,6 +568,7 @@ type ABitOfEverythingServiceCheckNestedEnumGetQueryParamsOpts struct {
 	NestedAnnotationAmount optional.Int64
 	Int64OverrideType optional.Int64
 	OutputOnlyStringViaFieldBehaviorAnnotation optional.String
+	OptionlStringValue optional.String
 }
 
 func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceCheckNestedEnumGetQueryParams(ctx context.Context, singleNestedOk string, floatValue float32, requiredStringViaFieldBehaviorAnnotation string, localVarOptionals *ABitOfEverythingServiceCheckNestedEnumGetQueryParamsOpts) (ExamplepbABitOfEverything, *http.Response, error) {
@@ -679,6 +686,9 @@ func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceCheckNestedEn
 	if localVarOptionals != nil && localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.IsSet() {
 		localVarQueryParams.Add("outputOnlyStringViaFieldBehaviorAnnotation", parameterToString(localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.Value(), ""))
 	}
+	if localVarOptionals != nil && localVarOptionals.OptionlStringValue.IsSet() {
+		localVarQueryParams.Add("optionlStringValue", parameterToString(localVarOptionals.OptionlStringValue.Value(), ""))
+	}
 	// to determine the Content-Type header
 	localVarHttpContentTypes := []string{"application/json", "application/x-foo-mime"}
 
@@ -838,6 +848,7 @@ ABitOfEverythingServiceApiService
      * @param "NestedAnnotationOk" (optional.String) -  DeepEnum description.   - FALSE: FALSE is false.  - TRUE: TRUE is true.
      * @param "Int64OverrideType" (optional.Int64) - 
      * @param "OutputOnlyStringViaFieldBehaviorAnnotation" (optional.String) -  mark a field as readonly in Open API definition.
+     * @param "OptionlStringValue" (optional.String) -  mark a field as optional.
 
 @return ExamplepbABitOfEverything
 */
@@ -873,6 +884,7 @@ type ABitOfEverythingServiceCheckPostQueryParamsOpts struct {
 	NestedAnnotationOk optional.String
 	Int64OverrideType optional.Int64
 	OutputOnlyStringViaFieldBehaviorAnnotation optional.String
+	OptionlStringValue optional.String
 }
 
 func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceCheckPostQueryParams(ctx context.Context, stringValue string, body ABitOfEverythingNested, floatValue float32, requiredStringViaFieldBehaviorAnnotation string, localVarOptionals *ABitOfEverythingServiceCheckPostQueryParamsOpts) (ExamplepbABitOfEverything, *http.Response, error) {
@@ -984,6 +996,9 @@ func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceCheckPostQuer
 	if localVarOptionals != nil && localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.IsSet() {
 		localVarQueryParams.Add("outputOnlyStringViaFieldBehaviorAnnotation", parameterToString(localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.Value(), ""))
 	}
+	if localVarOptionals != nil && localVarOptionals.OptionlStringValue.IsSet() {
+		localVarQueryParams.Add("optionlStringValue", parameterToString(localVarOptionals.OptionlStringValue.Value(), ""))
+	}
 	// to determine the Content-Type header
 	localVarHttpContentTypes := []string{"application/json", "application/x-foo-mime"}
 
@@ -2360,6 +2375,7 @@ ABitOfEverythingServiceApiService
      * @param "NestedAnnotationOk" (optional.String) -  DeepEnum description.   - FALSE: FALSE is false.  - TRUE: TRUE is true.
      * @param "Int64OverrideType" (optional.Int64) - 
      * @param "OutputOnlyStringViaFieldBehaviorAnnotation" (optional.String) -  mark a field as readonly in Open API definition.
+     * @param "OptionlStringValue" (optional.String) -  mark a field as optional.
 
 @return interface{}
 */
@@ -2398,6 +2414,7 @@ type ABitOfEverythingServiceGetQueryOpts struct {
 	NestedAnnotationOk optional.String
 	Int64OverrideType optional.Int64
 	OutputOnlyStringViaFieldBehaviorAnnotation optional.String
+	OptionlStringValue optional.String
 }
 
 func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceGetQuery(ctx context.Context, uuid string, floatValue float32, requiredStringViaFieldBehaviorAnnotation string, localVarOptionals *ABitOfEverythingServiceGetQueryOpts) (interface{}, *http.Response, error) {
@@ -2518,6 +2535,9 @@ func (a *ABitOfEverythingServiceApiService) ABitOfEverythingServiceGetQuery(ctx
 	if localVarOptionals != nil && localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.IsSet() {
 		localVarQueryParams.Add("outputOnlyStringViaFieldBehaviorAnnotation", parameterToString(localVarOptionals.OutputOnlyStringViaFieldBehaviorAnnotation.Value(), ""))
 	}
+	if localVarOptionals != nil && localVarOptionals.OptionlStringValue.IsSet() {
+		localVarQueryParams.Add("optionlStringValue", parameterToString(localVarOptionals.OptionlStringValue.Value(), ""))
+	}
 	// to determine the Content-Type header
 	localVarHttpContentTypes := []string{"application/json", "application/x-foo-mime"}
 
diff --git a/examples/internal/clients/abe/model_examplepb_a_bit_of_everything.go b/examples/internal/clients/abe/model_examplepb_a_bit_of_everything.go
index 5a258c2aa31..ac29cccc18a 100644
--- a/examples/internal/clients/abe/model_examplepb_a_bit_of_everything.go
+++ b/examples/internal/clients/abe/model_examplepb_a_bit_of_everything.go
@@ -60,4 +60,5 @@ type ExamplepbABitOfEverything struct {
 	Int64OverrideType int64 `json:"int64OverrideType,omitempty"`
 	RequiredStringViaFieldBehaviorAnnotation string `json:"requiredStringViaFieldBehaviorAnnotation"`
 	OutputOnlyStringViaFieldBehaviorAnnotation string `json:"outputOnlyStringViaFieldBehaviorAnnotation,omitempty"`
+	OptionlStringValue string `json:"optionlStringValue,omitempty"`
 }
diff --git a/examples/internal/proto/examplepb/a_bit_of_everything.pb.go b/examples/internal/proto/examplepb/a_bit_of_everything.pb.go
index 0a081081d5c..a549c33e801 100644
--- a/examples/internal/proto/examplepb/a_bit_of_everything.pb.go
+++ b/examples/internal/proto/examplepb/a_bit_of_everything.pb.go
@@ -188,6 +188,8 @@ type ABitOfEverything struct {
 	RequiredStringViaFieldBehaviorAnnotation string `protobuf:"bytes,38,opt,name=required_string_via_field_behavior_annotation,json=requiredStringViaFieldBehaviorAnnotation,proto3" json:"required_string_via_field_behavior_annotation,omitempty"`
 	// mark a field as readonly in Open API definition
 	OutputOnlyStringViaFieldBehaviorAnnotation string `protobuf:"bytes,39,opt,name=output_only_string_via_field_behavior_annotation,json=outputOnlyStringViaFieldBehaviorAnnotation,proto3" json:"output_only_string_via_field_behavior_annotation,omitempty"`
+	// mark a field as optional
+	OptionlStringValue *string `protobuf:"bytes,40,opt,name=optionl_string_value,json=optionlStringValue,proto3,oneof" json:"optionl_string_value,omitempty"`
 }
 
 func (x *ABitOfEverything) Reset() {
@@ -495,6 +497,13 @@ func (x *ABitOfEverything) GetOutputOnlyStringViaFieldBehaviorAnnotation() strin
 	return ""
 }
 
+func (x *ABitOfEverything) GetOptionlStringValue() string {
+	if x != nil && x.OptionlStringValue != nil {
+		return *x.OptionlStringValue
+	}
+	return ""
+}
+
 type isABitOfEverything_OneofValue interface {
 	isABitOfEverything_OneofValue()
 }
@@ -1139,7 +1148,7 @@ var file_examples_internal_proto_examplepb_a_bit_of_everything_proto_rawDesc = [
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 	0x79, 0x74, 0x68, 0x69, 0x6e, 0x67, 0x52, 0x65, 0x70, 0x65, 0x61, 0x74, 0x65, 0x64, 0x12, 0x39,
 	0x0a, 0x19, 0x70, 0x61, 0x74, 0x68, 0x5f, 0x72, 0x65, 0x70, 0x65, 0x61, 0x74, 0x65, 0x64, 0x5f,
diff --git a/examples/internal/proto/examplepb/a_bit_of_everything.proto b/examples/internal/proto/examplepb/a_bit_of_everything.proto
index 1d58b3f2dc1..bc9f2805477 100644
--- a/examples/internal/proto/examplepb/a_bit_of_everything.proto
+++ b/examples/internal/proto/examplepb/a_bit_of_everything.proto
@@ -279,6 +279,9 @@ message ABitOfEverything {
 
 	// mark a field as readonly in Open API definition
 	string output_only_string_via_field_behavior_annotation = 39 [(google.api.field_behavior) = OUTPUT_ONLY];
+
+	// mark a field as optional
+	optional string optionl_string_value = 40;
 }
 
 // ABitOfEverythingRepeated is used to validate repeated path parameter functionality
diff --git a/examples/internal/proto/examplepb/a_bit_of_everything.swagger.json b/examples/internal/proto/examplepb/a_bit_of_everything.swagger.json
index 6bfcff12adf..bc0881eab4c 100644
--- a/examples/internal/proto/examplepb/a_bit_of_everything.swagger.json
+++ b/examples/internal/proto/examplepb/a_bit_of_everything.swagger.json
@@ -461,6 +461,13 @@
             "in": "query",
             "required": false,
             "type": "string"
+          },
+          {
+            "name": "optionlStringValue",
+            "description": "mark a field as optional.",
+            "in": "query",
+            "required": false,
+            "type": "string"
           }
         ],
         "tags": [
@@ -795,6 +802,13 @@
             "in": "query",
             "required": false,
             "type": "string"
+          },
+          {
+            "name": "optionlStringValue",
+            "description": "mark a field as optional.",
+            "in": "query",
+            "required": false,
+            "type": "string"
           }
         ],
         "tags": [
@@ -1118,6 +1132,13 @@
             "in": "query",
             "required": false,
             "type": "string"
+          },
+          {
+            "name": "optionlStringValue",
+            "description": "mark a field as optional.",
+            "in": "query",
+            "required": false,
+            "type": "string"
           }
         ],
         "tags": [
@@ -1459,6 +1480,13 @@
             "in": "query",
             "required": false,
             "type": "string"
+          },
+          {
+            "name": "optionlStringValue",
+            "description": "mark a field as optional.",
+            "in": "query",
+            "required": false,
+            "type": "string"
           }
         ],
         "tags": [
@@ -3058,6 +3086,10 @@
           "type": "string",
           "title": "mark a field as readonly in Open API definition",
           "readOnly": true
+        },
+        "optionlStringValue": {
+          "type": "string",
+          "title": "mark a field as optional"
         }
       },
       "description": "Intentionaly complicated message type to cover many features of Protobuf.",
diff --git a/examples/internal/proto/examplepb/stream.swagger.json b/examples/internal/proto/examplepb/stream.swagger.json
index 1d5d518e195..721d2807779 100644
--- a/examples/internal/proto/examplepb/stream.swagger.json
+++ b/examples/internal/proto/examplepb/stream.swagger.json
@@ -395,6 +395,10 @@
           "type": "string",
           "title": "mark a field as readonly in Open API definition",
           "readOnly": true
+        },
+        "optionlStringValue": {
+          "type": "string",
+          "title": "mark a field as optional"
         }
       },
       "description": "Intentionaly complicated message type to cover many features of Protobuf.",
diff --git a/protoc-gen-grpc-gateway/BUILD.bazel b/protoc-gen-grpc-gateway/BUILD.bazel
index 5aa586cbe56..28593f41bfc 100644
--- a/protoc-gen-grpc-gateway/BUILD.bazel
+++ b/protoc-gen-grpc-gateway/BUILD.bazel
@@ -12,6 +12,7 @@ go_library(
         "//protoc-gen-grpc-gateway/internal/gengateway:go_default_library",
         "@com_github_golang_glog//:go_default_library",
         "@org_golang_google_protobuf//compiler/protogen:go_default_library",
+        "@org_golang_google_protobuf//types/pluginpb:go_default_library",
     ],
 )
 
diff --git a/protoc-gen-grpc-gateway/main.go b/protoc-gen-grpc-gateway/main.go
index b838d50fbe7..5c36ee54c46 100644
--- a/protoc-gen-grpc-gateway/main.go
+++ b/protoc-gen-grpc-gateway/main.go
@@ -18,6 +18,7 @@ import (
 	"github.com/grpc-ecosystem/grpc-gateway/v2/internal/descriptor"
 	"github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-grpc-gateway/internal/gengateway"
 	"google.golang.org/protobuf/compiler/protogen"
+	"google.golang.org/protobuf/types/pluginpb"
 )
 
 var (
@@ -54,6 +55,7 @@ func main() {
 	protogen.Options{
 		ParamFunc: flag.CommandLine.Set,
 	}.Run(func(gen *protogen.Plugin) error {
+		gen.SupportedFeatures = uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)
 		reg := descriptor.NewRegistry()
 
 		err := applyFlags(reg)
diff --git a/protoc-gen-openapiv2/main.go b/protoc-gen-openapiv2/main.go
index ebcae17d004..ec0df07f637 100644
--- a/protoc-gen-openapiv2/main.go
+++ b/protoc-gen-openapiv2/main.go
@@ -146,7 +146,8 @@ func emitFiles(out []*descriptor.ResponseFile) {
 	for idx, item := range out {
 		files[idx] = item.CodeGeneratorResponse_File
 	}
-	emitResp(&pluginpb.CodeGeneratorResponse{File: files})
+	supportedFeatures := uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)
+	emitResp(&pluginpb.CodeGeneratorResponse{SupportedFeatures: &supportedFeatures, File: files})
 }
 
 func emitError(err error) {