feat: implement TrackableFilter for namespace

This change updates the namespace filter to implement the TrackableFilter
interface. This provides the functionality for the user to track which
fields were updated by the namespace filter.

api/filters/namespace/namespace.go

@@ -18,9 +18,17 @@ type Filter struct {
 
 	// FsSlice contains the FieldSpecs to locate the namespace field
 	FsSlice types.FsSlice `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
+
+	trackableSetter filtersutil.TrackableSetter
 }
 
 var _ kio.Filter = Filter{}
+var _ kio.TrackableFilter = &Filter{}
+
+// WithMutationTracker registers a callback which will be invoked each time a field is mutated
+func (ns *Filter) WithMutationTracker(callback func(key, value, tag string, node *yaml.RNode)) {
+	ns.trackableSetter.WithMutationTracker(callback)
+}
 
 func (ns Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
 	return kio.FilterAll(yaml.FilterFunc(ns.run)).Filter(nodes)
@@ -44,7 +52,7 @@ func (ns Filter) run(node *yaml.RNode) (*yaml.RNode, error) {
 	// transformations based on data -- :)
 	err := node.PipeE(fsslice.Filter{
 		FsSlice:    ns.FsSlice,
-		SetValue:   filtersutil.SetScalar(ns.Namespace),
+		SetValue:   ns.trackableSetter.SetScalar(ns.Namespace),
 		CreateKind: yaml.ScalarNode, // Namespace is a ScalarNode
 		CreateTag:  yaml.NodeTagString,
 	})
@@ -77,7 +85,7 @@ func (ns Filter) metaNamespaceHack(obj *yaml.RNode, gvk resid.Gvk) error {
 		FsSlice: []types.FieldSpec{
 			{Path: types.MetadataNamespacePath, CreateIfNotPresent: true},
 		},
-		SetValue:   filtersutil.SetScalar(ns.Namespace),
+		SetValue:   ns.trackableSetter.SetScalar(ns.Namespace),
 		CreateKind: yaml.ScalarNode, // Namespace is a ScalarNode
 	}
 	_, err := f.Filter(obj)
@@ -123,11 +131,15 @@ func (ns Filter) roleBindingHack(obj *yaml.RNode, gvk resid.Gvk) error {
 		}
 
 		// set the namespace for the default account
-		v := yaml.NewScalarRNode(ns.Namespace)
-		return o.PipeE(
+		node, err := o.Pipe(
 			yaml.LookupCreate(yaml.ScalarNode, "namespace"),
-			yaml.FieldSetter{Value: v},
 		)
+		if err != nil {
+			return err
+		}
+
+		return ns.trackableSetter.SetScalar(ns.Namespace)(node)
+
 	})
 
 	return err

api/filters/namespace/namespace_test.go

@@ -12,8 +12,11 @@ import (
 	"sigs.k8s.io/kustomize/api/internal/plugins/builtinconfig"
 	filtertest_test "sigs.k8s.io/kustomize/api/testutils/filtertest"
 	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
 )
 
+var mutationTrackerStub = filtertest_test.MutationTrackerStub{}
+
 var tests = []TestCase{
 	{
 		name: "add",
@@ -283,21 +286,91 @@ a:
 			},
 		},
 	},
+
+	{
+		name: "mutation tracker",
+		input: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+---
+apiVersion: example.com/v1
+kind: RoleBinding
+subjects:
+- name: default
+`,
+		expected: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+  namespace: bar
+a:
+  b:
+    c: bar
+---
+apiVersion: example.com/v1
+kind: RoleBinding
+subjects:
+- name: default
+  namespace: bar
+metadata:
+  namespace: bar
+a:
+  b:
+    c: bar
+`,
+		filter: namespace.Filter{Namespace: "bar"},
+		fsslice: []types.FieldSpec{
+			{
+				Path:               "a/b/c",
+				CreateIfNotPresent: true,
+			},
+		},
+		mutationTracker: mutationTrackerStub.MutationTracker,
+		expectedSetValueArgs: []filtertest_test.SetValueArg{
+			{
+				Value:    "bar",
+				NodePath: []string{"metadata", "namespace"},
+			},
+			{
+				Value:    "bar",
+				NodePath: []string{"a", "b", "c"},
+			},
+			{
+				Value:    "bar",
+				NodePath: []string{"metadata", "namespace"},
+			},
+			{
+				Value:    "bar",
+				NodePath: []string{"namespace"},
+			},
+			{
+				Value:    "bar",
+				NodePath: []string{"a", "b", "c"},
+			},
+		},
+	},
 }
 
 type TestCase struct {
-	name     string
-	input    string
-	expected string
-	filter   namespace.Filter
-	fsslice  types.FsSlice
+	name                 string
+	input                string
+	expected             string
+	filter               namespace.Filter
+	fsslice              types.FsSlice
+	mutationTracker      func(key, value, tag string, node *yaml.RNode)
+	expectedSetValueArgs []filtertest_test.SetValueArg
 }
 
 var config = builtinconfig.MakeDefaultConfig()
 
 func TestNamespace_Filter(t *testing.T) {
 	for i := range tests {
+		mutationTrackerStub.Reset()
 		test := tests[i]
+		test.filter.WithMutationTracker(test.mutationTracker)
 		t.Run(test.name, func(t *testing.T) {
 			test.filter.FsSlice = append(config.NameSpace, test.fsslice...)
 			if !assert.Equal(t,
@@ -306,6 +379,7 @@ func TestNamespace_Filter(t *testing.T) {
 					filtertest_test.RunFilter(t, test.input, test.filter))) {
 				t.FailNow()
 			}
+			assert.Equal(t, test.expectedSetValueArgs, mutationTrackerStub.SetValueArgs())
 		})
 	}
 }