fix namespace transformer for cluster-scoped resources

pkg/transformers/namespace.go

@@ -48,25 +48,28 @@ func NewNamespaceTransformer(ns string, cf []config.FieldSpec) Transformer {
 
 // Transform adds the namespace.
 func (o *namespaceTransformer) Transform(m resmap.ResMap) error {
-	mf := resmap.ResMap{}
-
-	for id := range m {
-		found := false
-		for _, path := range o.fieldSpecsToSkip {
-			if id.Gvk().IsSelected(&path.Gvk) {
-				found = true
-				break
-			}
-		}
-		if !found {
-			mf[id] = m[id]
-			delete(m, id)
-		}
-	}
+	mf := o.filterResmap(m)
 
 	for id := range mf {
 		objMap := mf[id].Map()
 		for _, path := range o.fieldSpecsToUse {
+			switch path.Path {
+			// Special casing .metadata.namespace since it is a common metadata field across all runtime.Object
+			// We should add namespace if it's namespaced resource; otherwise, we should not.
+			case "metadata/namespace":
+				if id.Gvk().IsSelected(&path.Gvk) && !id.Gvk().IsClusterKind() {
+					if len(objMap) > 0 {
+						err := mutateField(
+							objMap, path.PathSlice(), path.CreateIfNotPresent,
+							func(_ interface{}) (interface{}, error) {
+								return o.namespace, nil
+							})
+						if err != nil {
+							return err
+						}
+					}
+				}
+			default:
 				if !id.Gvk().IsSelected(&path.Gvk) {
 					continue
 				}
@@ -81,15 +84,39 @@ func (o *namespaceTransformer) Transform(m resmap.ResMap) error {
 						return err
 					}
 				}
-			newid := id.CopyWithNewNamespace(o.namespace)
-			m[newid] = mf[id]
 			}
 
+			if !id.Gvk().IsClusterKind() {
+				newid := id.CopyWithNewNamespace(o.namespace)
+				m[newid] = mf[id]
+			} else {
+				m[id] = mf[id]
+			}
+		}
 	}
 	o.updateClusterRoleBinding(m)
 	return nil
 }
 
+func (o *namespaceTransformer) filterResmap(m resmap.ResMap) resmap.ResMap {
+	mf := resmap.ResMap{}
+	for id := range m {
+		found := false
+		for _, path := range o.fieldSpecsToSkip {
+			if id.Gvk().IsSelected(&path.Gvk) {
+				found = true
+				mf[id] = m[id]
+				delete(m, id)
+			}
+		}
+		if !found {
+			mf[id] = m[id]
+			delete(m, id)
+		}
+	}
+	return mf
+}
+
 func (o *namespaceTransformer) updateClusterRoleBinding(m resmap.ResMap) {
 	saMap := map[string]bool{}
 	for id := range m {