some improvement to client-gen

cmd/libs/go2idl/client-gen/generators/client_generator.go

@@ -19,7 +19,6 @@ package generators
 
 import (
 	"fmt"
-	"os"
 	"path/filepath"
 	"strings"
 
@@ -107,15 +106,13 @@ func packageForGroup(gv unversioned.GroupVersion, typeList []*types.Type, packag
 			})
 
 			expansionFileName := "generated_expansion"
-			// To avoid overriding user's manual modification, only generate the expansion file if it doesn't exist.
-			if _, err := os.Stat(filepath.Join(srcTreePath, outputPackagePath, expansionFileName+".go")); os.IsNotExist(err) {
 			generators = append(generators, &genExpansion{
+				groupPath: filepath.Join(srcTreePath, outputPackagePath),
 				DefaultGen: generator.DefaultGen{
 					OptionalName: expansionFileName,
 				},
 				types: typeList,
 			})
-			}
 
 			return generators
 		},

cmd/libs/go2idl/client-gen/generators/generator_for_expansion.go

@@ -18,6 +18,9 @@ package generators
 
 import (
 	"io"
+	"os"
+	"path/filepath"
+	"strings"
 
 	"k8s.io/kubernetes/cmd/libs/go2idl/generator"
 	"k8s.io/kubernetes/cmd/libs/go2idl/types"
@@ -26,6 +29,7 @@ import (
 // genExpansion produces a file for a group client, e.g. ExtensionsClient for the extension group.
 type genExpansion struct {
 	generator.DefaultGen
+	groupPath string
 	// types in a group
 	types []*types.Type
 }
@@ -38,8 +42,10 @@ func (g *genExpansion) Filter(c *generator.Context, t *types.Type) bool {
 func (g *genExpansion) GenerateType(c *generator.Context, t *types.Type, w io.Writer) error {
 	sw := generator.NewSnippetWriter(w, c, "$", "$")
 	for _, t := range g.types {
+		if _, err := os.Stat(filepath.Join(g.groupPath, strings.ToLower(t.Name.Name+"_expansion.go"))); os.IsNotExist(err) {
 			sw.Do(expansionInterfaceTemplate, t)
 		}
+	}
 	return sw.Error()
 }