Make support paths option

Make protoc-gen-grpc-gateway support paths option such like golang/protobuf#515.

protoc-gen-grpc-gateway/gengateway/generator.go

@@ -19,15 +19,23 @@ var (
 	errNoTargetService = errors.New("no target service defined in the file")
 )
 
+type pathType int
+
+const (
+	pathTypeImport pathType = iota
+	pathTypeSourceRelative
+)
+
 type generator struct {
 	reg                *descriptor.Registry
 	baseImports        []descriptor.GoPackage
 	useRequestContext  bool
 	registerFuncSuffix string
+	pathType           pathType
 }
 
 // New returns a new generator which generates grpc gateway files.
-func New(reg *descriptor.Registry, useRequestContext bool, registerFuncSuffix string) gen.Generator {
+func New(reg *descriptor.Registry, useRequestContext bool, registerFuncSuffix, pathTypeString string) gen.Generator {
 	var imports []descriptor.GoPackage
 	for _, pkgpath := range []string{
 		"io",
@@ -57,11 +65,23 @@ func New(reg *descriptor.Registry, useRequestContext bool, registerFuncSuffix st
 		}
 		imports = append(imports, pkg)
 	}
+
+	var pathType pathType
+	switch pathTypeString {
+	case "", "import":
+		// paths=import is default
+	case "source_relative":
+		pathType = pathTypeSourceRelative
+	default:
+		glog.Fatalf(`Unknown path type %q: want "import" or "source_relative".`, pathTypeString)
+	}
+
 	return &generator{
 		reg:                reg,
 		baseImports:        imports,
 		useRequestContext:  useRequestContext,
 		registerFuncSuffix: registerFuncSuffix,
+		pathType:           pathType,
 	}
 }
 
@@ -83,7 +103,7 @@ func (g *generator) Generate(targets []*descriptor.File) ([]*plugin.CodeGenerato
 			return nil, err
 		}
 		name := file.GetName()
-		if file.GoPkg.Path != "" {
+		if g.pathType == pathTypeImport && file.GoPkg.Path != "" {
 			name = fmt.Sprintf("%s/%s", file.GoPkg.Path, filepath.Base(name))
 		}
 		ext := filepath.Ext(name)

protoc-gen-grpc-gateway/gengateway/generator_test.go

@@ -101,6 +101,7 @@ func TestGenerateServiceWithoutBindings(t *testing.T) {
 func TestGenerateOutputPath(t *testing.T) {
 	cases := []struct {
 		file     *descriptor.File
+		pathType pathType
 		expected string
 	}{
 		{
@@ -121,10 +122,31 @@ func TestGenerateOutputPath(t *testing.T) {
 			),
 			expected: "example",
 		},
+		{
+			file: newExampleFileDescriptorWithGoPkg(
+				&descriptor.GoPackage{
+					Path: "example.com/path/to/example",
+					Name: "example_pb",
+				},
+			),
+			pathType: pathTypeSourceRelative,
+			expected: ".",
+		},
+		{
+			file: newExampleFileDescriptorWithGoPkg(
+				&descriptor.GoPackage{
+					Path: "example",
+					Name: "example_pb",
+				},
+			),
+			pathType: pathTypeSourceRelative,
+			expected: ".",
+		},
 	}
 
-	g := &generator{}
 	for _, c := range cases {
+		g := &generator{pathType: c.pathType}
+
 		file := c.file
 		gots, err := g.Generate([]*descriptor.File{crossLinkFixture(file)})
 		if err != nil {

protoc-gen-grpc-gateway/main.go

@@ -28,6 +28,7 @@ var (
 	useRequestContext    = flag.Bool("request_context", true, "determine whether to use http.Request's context or not")
 	allowDeleteBody      = flag.Bool("allow_delete_body", false, "unless set, HTTP DELETE methods may not have a body")
 	grpcAPIConfiguration = flag.String("grpc_api_configuration", "", "path to gRPC API Configuration in YAML format")
+	pathType             = flag.String("paths", "", "specifies how the paths of generated files are structured")
 )
 
 func main() {
@@ -62,7 +63,7 @@ func main() {
 		}
 	}
 
-	g := gengateway.New(reg, *useRequestContext, *registerFuncSuffix)
+	g := gengateway.New(reg, *useRequestContext, *registerFuncSuffix, *pathType)
 
 	if *grpcAPIConfiguration != "" {
 		if err := reg.LoadGrpcAPIServiceFromYAML(*grpcAPIConfiguration); err != nil {