ManagedFieldsObjectTracker: Reload scheme

In controller-runtime it is generally not expected to do any sort of
scheme registration if unstructured.Unstructured is used. To make this
work in the fakeclient, the fakeclient will register unstructured to
scheme if the scheme doesn't recognize the GVK.

This currently doesn't work with the `ManagedFieldsObjectTracker` as it
never reloads the scheme. This change makes it reload the scheme in an
inefficient but simple manner, which should be good enough for unit
tests.

staging/src/k8s.io/client-go/testing/fixture.go

@@ -631,7 +631,7 @@ type managedFieldObjectTracker struct {
 	ObjectTracker
 	scheme          ObjectScheme
 	objectConverter runtime.ObjectConvertor
-	mapper          meta.RESTMapper
+	mapper          func() meta.RESTMapper
 	typeConverter   managedfields.TypeConverter
 }
 
@@ -644,8 +644,10 @@ func NewFieldManagedObjectTracker(scheme *runtime.Scheme, decoder runtime.Decode
 		ObjectTracker:   NewObjectTracker(scheme, decoder),
 		scheme:          scheme,
 		objectConverter: scheme,
-		mapper:          testrestmapper.TestOnlyStaticRESTMapper(scheme),
-		typeConverter:   typeConverter,
+		mapper: func() meta.RESTMapper {
+			return testrestmapper.TestOnlyStaticRESTMapper(scheme)
+		},
+		typeConverter: typeConverter,
 	}
 }
 
@@ -654,7 +656,7 @@ func (t *managedFieldObjectTracker) Create(gvr schema.GroupVersionResource, obj
 	if err != nil {
 		return err
 	}
-	gvk, err := t.mapper.KindFor(gvr)
+	gvk, err := t.mapper().KindFor(gvr)
 	if err != nil {
 		return err
 	}
@@ -698,8 +700,9 @@ func (t *managedFieldObjectTracker) Update(gvr schema.GroupVersionResource, obj
 	if err != nil {
 		return err
 	}
-	gvk, err := t.mapper.KindFor(gvr)
+	gvk, err := t.mapper().KindFor(gvr)
 	if err != nil {
+		println("kindfor")
 		return err
 	}
 	mgr, err := t.fieldManagerFor(gvk)
@@ -728,7 +731,7 @@ func (t *managedFieldObjectTracker) Patch(gvr schema.GroupVersionResource, patch
 	if err != nil {
 		return err
 	}
-	gvk, err := t.mapper.KindFor(gvr)
+	gvk, err := t.mapper().KindFor(gvr)
 	if err != nil {
 		return err
 	}
@@ -757,7 +760,7 @@ func (t *managedFieldObjectTracker) Apply(gvr schema.GroupVersionResource, apply
 	if err != nil {
 		return err
 	}
-	gvk, err := t.mapper.KindFor(gvr)
+	gvk, err := t.mapper().KindFor(gvr)
 	if err != nil {
 		return err
 	}

staging/src/k8s.io/client-go/testing/fixture_test.go

@@ -661,3 +661,25 @@ var configMapTypedSchema = typed.YAMLObject(`types:
       namedType: __untyped_deduced_
     elementRelationship: separable
 `)
+
+func TestManagedFieldsObjectTrackerReloadsScheme(t *testing.T) {
+	cmResource := schema.GroupVersionResource{Version: "v1", Resource: "configmaps"}
+	scheme := runtime.NewScheme()
+	codecs := serializer.NewCodecFactory(scheme)
+
+	// Create tracker without registered ConfigMap type
+	tracker := NewFieldManagedObjectTracker(scheme, codecs.UniversalDecoder(), configMapTypeConverter(scheme))
+
+	cm := &v1.ConfigMap{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-cm",
+		},
+		Data: map[string]string{"key": "value"},
+	}
+
+	// Register the type in scheme
+	scheme.AddKnownTypes(cmResource.GroupVersion(), &v1.ConfigMap{})
+
+	err := tracker.Create(cmResource, cm, "default", metav1.CreateOptions{FieldManager: "test-manager"})
+	assert.NoError(t, err, "Create should succeed after registering type")
+}