Add option to disable protobuf generation

README.md

@@ -149,6 +149,20 @@ $ protoc --go-plugin_out=. --go-plugin_opt=paths=source_relative greeting.proto
 
 Then, you will find 4 files generated in the same directory, `greet.pb.go`, `greet_host.pb.go`, `greet_plugin.pb.go` and `greet_vtproto.pb.go`.
 
+#### Optional: Skip the go protobuf generation
+
+If the plugin should be used together with other generators like
+[`protoc-gen-go`](https://pkg.go.dev/github.com/golang/protobuf/protoc-gen-go),
+then it may be helpful to skip the standard protobuf generation. This can be
+done by setting the option `disable_pb_gen=true`, for example:
+
+```shell
+$ protoc \
+    --go_opt=paths=source_relative --go_out=. \
+    --go-plugin_opt=paths=source_relative,disable_pb_gen=true --go-plugin_out=. \
+    greeting.proto
+```
+
 ### Implement a plugin
 The `Greeter` interface is generated as below in the previous step. 
 
@@ -520,4 +534,4 @@ Welcome your contribution :)
 
 [releases]: https://github.com/knqyf263/go-plugin/releases
 
-[semver]: https://semver.org/
+[semver]: https://semver.org/

cmd/protoc-gen-go-plugin/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+
 	"google.golang.org/protobuf/compiler/protogen"
 	"google.golang.org/protobuf/types/pluginpb"
 
@@ -10,6 +11,7 @@ import (
 
 func main() {
 	var flags flag.FlagSet
+	disablePbGen := flags.Bool("disable_pb_gen", false, "disable .pb.go generation")
 	protogen.Options{ParamFunc: flags.Set}.Run(func(plugin *protogen.Plugin) error {
 		g, err := gen.NewGenerator(plugin)
 		if err != nil {
@@ -20,7 +22,7 @@ func main() {
 			if !f.Generate {
 				continue
 			}
-			g.GenerateFiles(f)
+			g.GenerateFiles(f, gen.Options{DisablePBGen: *disablePbGen})
 		}
 
 		plugin.SupportedFeatures = uint64(pluginpb.CodeGeneratorResponse_FEATURE_PROTO3_OPTIONAL)

gen/main.go

@@ -89,6 +89,10 @@ type Generator struct {
 	vtgen  *vtgenerator.Generator
 }
 
+type Options struct {
+	DisablePBGen bool
+}
+
 func NewGenerator(plugin *protogen.Plugin) (*Generator, error) {
 	ext := &vtgenerator.Extensions{}
 	featureNames := []string{"marshal", "unmarshal", "size"}
@@ -138,18 +142,22 @@ func replaceImport(m *protogen.Message) {
 }
 
 // GenerateFiles generates the contents of a .pb.go file.
-func (gg *Generator) GenerateFiles(file *protogen.File) *protogen.GeneratedFile {
+func (gg *Generator) GenerateFiles(file *protogen.File, opts Options) *protogen.GeneratedFile {
 	f := gg.newFileInfo(file)
-	gg.generatePBFile(f)
+	gg.generatePBFile(f, opts.DisablePBGen)
 	gg.generateHostFile(f)
 	gg.generatePluginFile(f)
 	gg.generateVTFile(f)
 	gg.generateOptionsFile(f)
 	return nil
 }
 
-func (gg *Generator) generatePBFile(f *fileInfo) {
-	filename := f.GeneratedFilenamePrefix + ".pb.go"
+func (gg *Generator) generatePBFile(f *fileInfo, disabled bool) {
+	filename := f.GeneratedFilenamePrefix
+	if disabled {
+		filename += "_service"
+	}
+	filename += ".pb.go"
 	g := gg.plugin.NewGeneratedFile(filename, f.GoImportPath)
 
 	gg.generateHeader(g, f)
@@ -165,14 +173,16 @@ func (gg *Generator) generatePBFile(f *fileInfo) {
 		g.P()
 	}
 
-	for i, imps := 0, f.Desc.Imports(); i < imps.Len(); i++ {
-		gg.genImport(g, f, imps.Get(i))
-	}
-	for _, enum := range f.allEnums {
-		genEnum(g, f, enum)
-	}
-	for _, message := range f.allMessages {
-		genMessage(g, f, message)
+	if !disabled {
+		for i, imps := 0, f.Desc.Imports(); i < imps.Len(); i++ {
+			gg.genImport(g, f, imps.Get(i))
+		}
+		for _, enum := range f.allEnums {
+			genEnum(g, f, enum)
+		}
+		for _, message := range f.allMessages {
+			genMessage(g, f, message)
+		}
 	}
 	for _, service := range f.allServices {
 		genServiceInterface(g, f, service)
@@ -252,7 +262,7 @@ func (gg *Generator) genImport(g *protogen.GeneratedFile, f *fileInfo, imp proto
 
 	// Generate public imports by generating the imported file, parsing it,
 	// and extracting every symbol that should receive a forwarding declaration.
-	impGen := gg.GenerateFiles(impFile)
+	impGen := gg.GenerateFiles(impFile, Options{})
 	impGen.Skip()
 	b, err := impGen.Content()
 	if err != nil {