protoc-gen-go: indicate deprecated fields in documentation

protoc-gen-go/generator/generator.go

@@ -1330,7 +1330,11 @@ func (g *Generator) generate(file *FileDescriptor) {
 // Generate the header, including package definition
 func (g *Generator) generateHeader() {
 	g.P("// Code generated by protoc-gen-go. DO NOT EDIT.")
-	g.P("// source: ", g.file.Name)
+	if g.file.GetOptions().GetDeprecated() {
+		g.P("// ", g.file.Name, " is a deprecated file.")
+	} else {
+		g.P("// source: ", g.file.Name)
+	}
 	g.P()
 
 	name := g.file.PackageName()
@@ -1374,6 +1378,10 @@ func (g *Generator) generateHeader() {
 	g.P()
 }
 
+// deprecationComment is the standard comment added to deprecated
+// messages, fields, enums, and enum values.
+var deprecationComment = "// Deprecated: Do not use."
+
 // PrintComments prints any comments from the source .proto file.
 // The path is a comma-separated list of integers.
 // It returns an indication of whether any comments were printed.
@@ -1488,17 +1496,26 @@ func (g *Generator) generateEnum(enum *EnumDescriptor) {
 	ccTypeName := CamelCaseSlice(typeName)
 	ccPrefix := enum.prefix()
 
+	deprecatedEnum := ""
+	if enum.GetOptions().GetDeprecated() {
+		deprecatedEnum = deprecationComment
+	}
 	g.PrintComments(enum.path)
-	g.P("type ", Annotate(enum.file, enum.path, ccTypeName), " int32")
+	g.P("type ", Annotate(enum.file, enum.path, ccTypeName), " int32", deprecatedEnum)
 	g.file.addExport(enum, enumSymbol{ccTypeName, enum.proto3()})
 	g.P("const (")
 	g.In()
 	for i, e := range enum.Value {
 		etorPath := fmt.Sprintf("%s,%d,%d", enum.path, enumValuePath, i)
 		g.PrintComments(etorPath)
 
+		deprecatedValue := ""
+		if e.GetOptions().GetDeprecated() {
+			deprecatedValue = deprecationComment
+		}
+
 		name := ccPrefix + *e.Name
-		g.P(Annotate(enum.file, etorPath, name), " ", ccTypeName, " = ", e.Number)
+		g.P(Annotate(enum.file, etorPath, name), " ", ccTypeName, " = ", e.Number, " ", deprecatedValue)
 		g.file.addExport(enum, constOrVarSymbol{name, "const", ccTypeName})
 	}
 	g.Out()
@@ -1839,7 +1856,18 @@ func (g *Generator) generateMessage(message *Descriptor) {
 	oneofTypeName := make(map[*descriptor.FieldDescriptorProto]string) // without star
 	oneofInsertPoints := make(map[int32]int)                           // oneof_index => offset of g.Buffer
 
-	g.PrintComments(message.path)
+	comments := g.PrintComments(message.path)
+
+	// Guarantee deprecation comments appear after user-provided comments.
+	if message.GetOptions().GetDeprecated() {
+		if comments {
+			// Convention: Separate deprecation comments from original
+			// comments with an empty line.
+			g.P("//")
+		}
+		g.P(deprecationComment)
+	}
+
 	g.P("type ", Annotate(message.file, message.path, ccTypeName), " struct {")
 	g.In()
 
@@ -1965,9 +1993,14 @@ func (g *Generator) generateMessage(message *Descriptor) {
 			continue
 		}
 
+		fieldDeprecated := ""
+		if field.GetOptions().GetDeprecated() {
+			fieldDeprecated = deprecationComment
+		}
+
 		fieldFullPath := fmt.Sprintf("%s,%d,%d", message.path, messageFieldPath, i)
 		g.PrintComments(fieldFullPath)
-		g.P(Annotate(message.file, fieldFullPath, fieldName), "\t", typename, "\t`", tag, "`")
+		g.P(Annotate(message.file, fieldFullPath, fieldName), "\t", typename, "\t`", tag, "`", fieldDeprecated)
 		g.RecordTypeUse(field.GetTypeName())
 	}
 	g.P("XXX_NoUnkeyedLiteral\tstruct{} `json:\"-\"`") // prevent unkeyed struct literals
@@ -2252,6 +2285,10 @@ func (g *Generator) generateMessage(message *Descriptor) {
 			})
 		}
 
+		if field.GetOptions().GetDeprecated() {
+			g.P(deprecationComment)
+		}
+
 		g.P("func (m *", ccTypeName, ") ", Annotate(message.file, fieldFullPath, mname), "() "+typename+" {")
 		g.In()
 		def, hasDef := defNames[field]

protoc-gen-go/grpc/grpc.go

@@ -138,11 +138,15 @@ func (g *grpc) GenerateImports(file *generator.FileDescriptor) {
 
 // reservedClientName records whether a client name is reserved on the client side.
 var reservedClientName = map[string]bool{
-// TODO: do we need any in gRPC?
+	// TODO: do we need any in gRPC?
 }
 
 func unexport(s string) string { return strings.ToLower(s[:1]) + s[1:] }
 
+// deprecationComment is the standard comment added to deprecated
+// messages, fields, enums, and enum values.
+var deprecationComment = "// Deprecated: Do not use."
+
 // generateService generates all the code for the named service.
 func (g *grpc) generateService(file *generator.FileDescriptor, service *pb.ServiceDescriptorProto, index int) {
 	path := fmt.Sprintf("6,%d", index) // 6 means service.
@@ -153,12 +157,16 @@ func (g *grpc) generateService(file *generator.FileDescriptor, service *pb.Servi
 		fullServName = pkg + "." + fullServName
 	}
 	servName := generator.CamelCase(origServName)
+	deprecated := service.GetOptions().GetDeprecated()
 
 	g.P()
 	g.P("// Client API for ", servName, " service")
 	g.P()
 
 	// Client interface.
+	if deprecated {
+		g.P(deprecationComment)
+	}
 	g.P("type ", servName, "Client interface {")
 	for i, method := range service.Method {
 		g.gen.PrintComments(fmt.Sprintf("%s,2,%d", path, i)) // 2 means method in a service.
@@ -174,6 +182,9 @@ func (g *grpc) generateService(file *generator.FileDescriptor, service *pb.Servi
 	g.P()
 
 	// NewClient factory.
+	if deprecated {
+		g.P(deprecationComment)
+	}
 	g.P("func New", servName, "Client (cc *", grpcPkg, ".ClientConn) ", servName, "Client {")
 	g.P("return &", unexport(servName), "Client{cc}")
 	g.P("}")
@@ -200,6 +211,9 @@ func (g *grpc) generateService(file *generator.FileDescriptor, service *pb.Servi
 	g.P()
 
 	// Server interface.
+	if deprecated {
+		g.P(deprecationComment)
+	}
 	serverType := servName + "Server"
 	g.P("type ", serverType, " interface {")
 	for i, method := range service.Method {
@@ -210,6 +224,9 @@ func (g *grpc) generateService(file *generator.FileDescriptor, service *pb.Servi
 	g.P()
 
 	// Server registration.
+	if deprecated {
+		g.P(deprecationComment)
+	}
 	g.P("func Register", servName, "Server(s *", grpcPkg, ".Server, srv ", serverType, ") {")
 	g.P("s.RegisterService(&", serviceDescVar, `, srv)`)
 	g.P("}")
@@ -283,6 +300,9 @@ func (g *grpc) generateClientMethod(servName, fullServName, serviceDescVar strin
 	inType := g.typeName(method.GetInputType())
 	outType := g.typeName(method.GetOutputType())
 
+	if method.GetOptions().GetDeprecated() {
+		g.P(deprecationComment)
+	}
 	g.P("func (c *", unexport(servName), "Client) ", g.generateClientSignature(servName, method), "{")
 	if !method.GetServerStreaming() && !method.GetClientStreaming() {
 		g.P("out := new(", outType, ")")

protoc-gen-go/testdata/Makefile

@@ -51,6 +51,17 @@ golden:
 	gofmt -w my_test/test.pb.go
 	diff -w my_test/test.pb.go my_test/test.pb.go.golden
 
+	make -B deprecated/deprecated.pb.go
+	sed -i -e '/return.*fileDescriptor/d' deprecated/deprecated.pb.go
+	sed -i -e '/^var fileDescriptor/,/^}/d' deprecated/deprecated.pb.go
+	sed -i -e '/proto.RegisterFile.*fileDescriptor/d' deprecated/deprecated.pb.go
+	gofmt -w deprecated/deprecated.pb.go
+	diff -w deprecated/deprecated.pb.go deprecated/deprecated.pb.go.golden
+
+
+deprecated/deprecated.pb.go: deprecated/deprecated.proto
+	protoc --go_out=plugins=grpc,import_path=Mdeprecated/deprecated.proto=github.com/golang/protobuf/protoc-gen-go/testdata/deprecated:. $<
+
 nuke:	clean
 
 testbuild:	regenerate