Fix protoc-gen-go-fieldpath

The generator has to handle nested fields such as
902212651b/api/events/container.proto (L31-L35).

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

cmd/protoc-gen-go-fieldpath/generator.go

@@ -130,7 +130,7 @@ func (gen *generator) genFieldMethod(m *protogen.Message) {
 }
 
 func isMessageField(f *protogen.Field) bool {
-	return f.Desc.Kind() == protoreflect.MessageKind && f.GoIdent.GoName != "Timestamp"
+	return f.Desc.Kind() == protoreflect.MessageKind && f.Desc.Cardinality() != protoreflect.Repeated && f.Message.GoIdent.GoName != "Timestamp"
 }
 
 func isLabelsField(f *protogen.Field) bool {
@@ -138,7 +138,24 @@ func isLabelsField(f *protogen.Field) bool {
 }
 
 func isAnyField(f *protogen.Field) bool {
-	return f.Desc.Kind() == protoreflect.MessageKind && f.GoIdent.GoName == "Any"
+	return f.Desc.Kind() == protoreflect.MessageKind && f.Message.GoIdent.GoName == "Any"
+}
+
+func collectChildlen(parent *protogen.Message) ([]*protogen.Message, error) {
+	var children []*protogen.Message
+	for _, child := range parent.Messages {
+		if child.Desc.IsMapEntry() {
+			continue
+		}
+		children = append(children, child)
+
+		xs, err := collectChildlen(child)
+		if err != nil {
+			return nil, err
+		}
+		children = append(children, xs...)
+	}
+	return children, nil
 }
 
 func generate(plugin *protogen.Plugin, input *protogen.File) error {
@@ -148,7 +165,18 @@ func generate(plugin *protogen.Plugin, input *protogen.File) error {
 	file.P("package ", input.GoPackageName)
 
 	gen := newGenerator(file)
+
+	var messages []*protogen.Message
 	for _, m := range input.Messages {
+		messages = append(messages, m)
+		children, err := collectChildlen(m)
+		if err != nil {
+			return err
+		}
+		messages = append(messages, children...)
+	}
+
+	for _, m := range messages {
 		gen.genFieldMethod(m)
 	}
 	return nil