Isolate generated ProtoMessage() methods in build-tagged files

hack/update-codegen.sh

@@ -145,6 +145,7 @@ function codegen::protobuf() {
     git_find -z \
         ':(glob)**/generated.proto' \
         ':(glob)**/generated.pb.go' \
+        ':(glob)**/generated.protomessage.pb.go' \
         | xargs -0 rm -f
 
     if kube::protoc::check_protoc >/dev/null; then

staging/src/k8s.io/apimachinery/pkg/runtime/serializer/protobuf/protobuf.go

@@ -320,8 +320,6 @@ type unbufferedMarshaller interface {
 
 // unmarshaler is the subset of gogo Message and Unmarshaler used by unmarshal
 type unmarshaler interface {
-	// Marker method, currently defined on all protoc-generated messages
-	ProtoMessage()
 	// Reset() is called on the top-level message before unmarshaling,
 	// and clears all existing data from the message instance.
 	Reset()

staging/src/k8s.io/code-generator/cmd/go-to-protobuf/protobuf/cmd.go

@@ -279,6 +279,7 @@ func Run(g *Generator) {
 
 		path := filepath.Join(g.OutputDir, p.ImportPath())
 		outputPath := filepath.Join(g.OutputDir, p.OutputPath())
+		protomessageOutputPath := filepath.Join(g.OutputDir, p.ProtomessageOutputPath())
 
 		// generate the gogoprotobuf protoc
 		cmd := exec.Command("protoc", append(args, path)...)
@@ -295,12 +296,17 @@ func Run(g *Generator) {
 
 		// alter the generated protobuf file to remove the generated types (but leave the serializers) and rewrite the
 		// package statement to match the desired package name
-		if err := RewriteGeneratedGogoProtobufFile(outputPath, p.ExtractGeneratedType, p.OptionalTypeName, buf.Bytes(), g.DropGogoGo); err != nil {
+		if err := RewriteGeneratedGogoProtobufFile(outputPath, protomessageOutputPath, p.ExtractGeneratedType, p.OptionalTypeName, buf.Bytes(), g.DropGogoGo); err != nil {
 			log.Fatalf("Unable to rewrite generated %s: %v", outputPath, err)
 		}
 
+		outputPaths := []string{outputPath}
+		if g.DropGogoGo {
+			outputPaths = append(outputPaths, protomessageOutputPath)
+		}
+
 		// sort imports
-		cmd = exec.Command("goimports", "-w", outputPath)
+		cmd = exec.Command("goimports", append([]string{"-w"}, outputPaths...)...)
 		out, err = cmd.CombinedOutput()
 		if len(out) > 0 {
 			log.Print(string(out))
@@ -311,7 +317,7 @@ func Run(g *Generator) {
 		}
 
 		// format and simplify the generated file
-		cmd = exec.Command("gofmt", "-s", "-w", outputPath)
+		cmd = exec.Command("gofmt", append([]string{"-s", "-w"}, outputPaths...)...)
 		out, err = cmd.CombinedOutput()
 		if len(out) > 0 {
 			log.Print(string(out))

staging/src/k8s.io/code-generator/cmd/go-to-protobuf/protobuf/package.go

@@ -80,7 +80,7 @@ type protobufPackage struct {
 }
 
 func (p *protobufPackage) Clean() error {
-	for _, s := range []string{p.ImportPath(), p.OutputPath()} {
+	for _, s := range []string{p.ImportPath(), p.OutputPath(), p.ProtomessageOutputPath()} {
 		if err := os.Remove(filepath.Join(p.Dir(), filepath.Base(s))); err != nil && !os.IsNotExist(err) {
 			return err
 		}
@@ -200,6 +200,10 @@ func (p *protobufPackage) OutputPath() string {
 	return filepath.Join(p.Path(), "generated.pb.go")
 }
 
+func (p *protobufPackage) ProtomessageOutputPath() string {
+	return filepath.Join(p.Path(), "generated.protomessage.pb.go")
+}
+
 var (
 	_ = generator.Target(&protobufPackage{})
 )

staging/src/k8s.io/code-generator/cmd/go-to-protobuf/protobuf/parser.go

@@ -27,6 +27,7 @@ import (
 	"go/token"
 	"os"
 	"reflect"
+	"regexp"
 	"strings"
 
 	customreflect "k8s.io/code-generator/third_party/forked/golang/reflect"
@@ -77,8 +78,46 @@ type ExtractFunc func(*ast.TypeSpec) bool
 // and should have its marshal functions adjusted to remove the 'Items' accessor.
 type OptionalFunc func(name string) bool
 
-func RewriteGeneratedGogoProtobufFile(name string, extractFn ExtractFunc, optionalFn OptionalFunc, header []byte, dropGogo bool) error {
-	return rewriteFile(name, header, func(fset *token.FileSet, file *ast.File) error {
+func RewriteGeneratedGogoProtobufFile(file, protomessageFile string, extractFn ExtractFunc, optionalFn OptionalFunc, header []byte, dropGogo bool) error {
+
+	// Optionally extract ProtoMessage() marker methods to a separate build-tagged file
+	if dropGogo {
+		data, err := os.ReadFile(file)
+		if err != nil {
+			return err
+		}
+
+		packageRE := regexp.MustCompile(`^package .*`)
+		wrotePackage := false
+
+		protomessageFuncRE := regexp.MustCompile(`^func \(.*\) ProtoMessage\(\) \{\}$`)
+
+		b := bytes.NewBuffer(nil)
+		// add build tag
+		b.WriteString("//go:build kubernetes_protomessage_one_more_release\n")
+		b.WriteString("// +build kubernetes_protomessage_one_more_release\n\n")
+		// add boilerplate
+		b.Write(header)
+		b.WriteString("\n// Code generated by go-to-protobuf. DO NOT EDIT.\n\n")
+		for _, line := range bytes.Split(data, []byte("\n")) {
+			// copy package
+			if packageRE.Match(line) && !wrotePackage {
+				b.Write(line)
+				b.WriteString("\n\n")
+				wrotePackage = true
+			}
+			// copy empty ProtoMessage impls
+			if protomessageFuncRE.Match(line) {
+				b.Write(line)
+				b.WriteString("\n\n")
+			}
+		}
+		if err := os.WriteFile(protomessageFile, b.Bytes(), os.FileMode(0644)); err != nil {
+			return err
+		}
+	}
+
+	return rewriteFile(file, header, func(fset *token.FileSet, file *ast.File) error {
 		cmap := ast.NewCommentMap(fset, file, file.Comments)
 
 		// transform methods that point to optional maps or slices
@@ -172,9 +211,8 @@ var keepFuncs = map[string]bool{
 	"valueToStringGenerated": true,
 
 	// unmarshal
-	"Reset":        true,
-	"ProtoMessage": true,
-	"Unmarshal":    true,
+	"Reset":     true,
+	"Unmarshal": true,
 
 	// marshal
 	"Size":                 true,