Proto3 optional field

Makefile

@@ -3,4 +3,4 @@ proto:
 	mkdir -p build
 	go build -o build/protoc-gen-go-json .
 	export PATH=$(CURDIR)/build/:$$PATH && \
-	    cd e2e && protoc --go_out=. --go-json_out=logtostderr=true,v=10:. *.proto
+	    protoc --go_out=. -I./e2e --go-json_out=logtostderr=true,v=10:. e2e/*.proto

e2e/e2e.proto

@@ -2,7 +2,7 @@ syntax = "proto3";
 
 package e2e;
 
-option go_package = ".;e2e";
+option go_package = "./e2e;e2e";
 
 // Basic just tests basic fields, including oneofs and so on that don't
 // generally work automatically with encoding/json.
@@ -15,6 +15,8 @@ message Basic {
   }
 
   map<string, string> map = 4;
+
+  optional string o = 5;
 }
 
 // Test nested types

e2e/e2e_service.proto

@@ -2,7 +2,7 @@ syntax = "proto3";
 
 package e2e;
 
-option go_package = ".;e2e";
+option go_package = "./e2e;e2e";
 
 import "e2e.proto";
 

e2e/e2e_test.go

@@ -10,6 +10,8 @@ import (
 
 func TestTable(t *testing.T) {
 	type basicWrapper struct{ Basic }
+	var optionalPresent = "present"
+	var optionalEmpty = ""
 	var cases = []struct {
 		Name string
 
@@ -54,6 +56,30 @@ func TestTable(t *testing.T) {
 			},
 			nil,
 		},
+
+		{
+			"optional present",
+			&Basic{
+				A: "hello",
+				B: &Basic_Int{
+					Int: 42,
+				},
+				O: &optionalPresent,
+			},
+			nil,
+		},
+
+		{
+			"optional empty",
+			&Basic{
+				A: "hello",
+				B: &Basic_Int{
+					Int: 42,
+				},
+				O: &optionalEmpty,
+			},
+			nil,
+		},
 	}
 
 	for _, tt := range cases {

go.mod

@@ -4,7 +4,6 @@ go 1.12
 
 require (
 	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
-	github.com/golang/protobuf v1.4.1
 	github.com/stretchr/testify v1.3.0
 	google.golang.org/protobuf v1.25.0
 )

go.sum

@@ -10,14 +10,12 @@ github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekf
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-github.com/golang/protobuf v1.3.2 h1:6nsPYzhq5kReh6QImI3k5qWzO4PEbvbIW2cwSfR/6xs=
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi5j83Wpe3EHw8=
 github.com/golang/protobuf v1.4.0-rc.1.0.20200221234624-67d41d38c208/go.mod h1:xKAWHe0F5eneWXFV3EuXVDTCmh+JuBKY0li0aMyXATA=
 github.com/golang/protobuf v1.4.0-rc.2/go.mod h1:LlEzMj4AhA7rCAGe4KMBDvJI+AwstrUpVNzEA03Pprs=
 github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:WU3c8KckQ9AFe+yFwt9sWVRKCVIyN9cPHBJSNnbL67w=
 github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
-github.com/golang/protobuf v1.4.1 h1:ZFgWrT+bLgsYPirOnRfKLYJLvssAegOj/hgyMFdJZe0=
 github.com/golang/protobuf v1.4.1/go.mod h1:U8fpvMrcmy5pZrNK1lt4xCsGvpyWQ/VVv6QDs8UjoX8=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
@@ -55,10 +53,8 @@ golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IV
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
-google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8 h1:Nw54tB0rB7hY/N0NQvRW8DG4Yk3Q6T9cu9RcFQDu1tc=
 google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
 google.golang.org/genproto v0.0.0-20190819201941-24fa4b261c55/go.mod h1:DMBHOl98Agz4BDEuKkezgsaosCRResVns1a3J2ZsMNc=
-google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013 h1:+kGHl1aib/qcwaRi1CbqBZ1rk19r85MNUf8HaBghugY=
 google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013/go.mod h1:NbSheEEYHJ7i3ixzK3sjbqSGDJWnxyFXZblF3eUsNvo=
 google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=
 google.golang.org/grpc v1.23.0/go.mod h1:Y5yQAOtifL1yxbo5wqy6BxZv8vAUGQwXBOALyacEbxg=

main.go

@@ -7,6 +7,7 @@ import (
 	"github.com/golang/glog"
 	"github.com/mitchellh/protoc-gen-go-json/gen"
 	"google.golang.org/protobuf/compiler/protogen"
+	"google.golang.org/protobuf/types/pluginpb"
 )
 
 var (
@@ -23,7 +24,7 @@ func main() {
 	protogen.Options{
 		ParamFunc: flag.CommandLine.Set,
 	}.Run(func(gp *protogen.Plugin) error {
-
+		gp.SupportedFeatures = uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)
 		opts := gen.Options{
 			EnumsAsInts:        *enumsAsInts,
 			EmitDefaults:       *emitDefaults,