implement TrackableFilter interface with imagetag

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

api/filters/imagetag/imagetag.go

@@ -4,6 +4,7 @@
 package imagetag
 
 import (
+	"sigs.k8s.io/kustomize/api/filters/filtersutil"
 	"sigs.k8s.io/kustomize/api/filters/fsslice"
 	"sigs.k8s.io/kustomize/api/types"
 	"sigs.k8s.io/kustomize/kyaml/kio"
@@ -22,9 +23,17 @@ type Filter struct {
 	// FsSlice contains the FieldSpecs to locate an image field,
 	// e.g. Path: "spec/myContainers[]/image"
 	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 (f *Filter) WithMutationTracker(callback func(key, value, tag string, node *yaml.RNode)) {
+	f.trackableSetter.WithMutationTracker(callback)
+}
 
 func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
 	_, err := kio.FilterAll(yaml.FilterFunc(f.filter)).Filter(nodes)
@@ -42,6 +51,7 @@ func (f Filter) filter(node *yaml.RNode) (*yaml.RNode, error) {
 		FsSlice: f.FsSlice,
 		SetValue: imageTagUpdater{
 			ImageTag:        f.ImageTag,
+			trackableSetter: f.trackableSetter,
 		}.SetImageValue,
 	}); err != nil {
 		return nil, err

api/filters/imagetag/imagetag_test.go

@@ -10,14 +10,35 @@ import (
 	"github.com/stretchr/testify/assert"
 	filtertest "sigs.k8s.io/kustomize/api/testutils/filtertest"
 	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
 )
 
+type setValueArg struct {
+	Key       string
+	Value     string
+	Tag       string
+	PrevValue string
+}
+
+var setValueArgs []setValueArg
+
+func setValueCallbackStub(key, value, tag string, node *yaml.RNode) {
+	setValueArgs = append(setValueArgs, setValueArg{
+		Key:       key,
+		Value:     value,
+		Tag:       tag,
+		PrevValue: node.YNode().Value,
+	})
+}
+
 func TestImageTagUpdater_Filter(t *testing.T) {
 	testCases := map[string]struct {
 		input                string
 		expectedOutput       string
 		filter               Filter
 		fsSlice              types.FsSlice
+		setValueCallback     func(key, value, tag string, node *yaml.RNode)
+		expectedSetValueArgs []setValueArg
 	}{
 		"ignore CustomResourceDefinition": {
 			input: `
@@ -658,17 +679,108 @@ spec:
 				},
 			},
 		},
+		"mutation tracker": {
+			input: `
+group: apps
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  template:
+    spec:
+      containers:
+      - image: nginx:1.7.9
+        name: nginx-tagged
+      - image: nginx:latest
+        name: nginx-latest
+      - image: foobar:1
+        name: replaced-with-digest
+      - image: postgres:1.8.0
+        name: postgresdb
+      initContainers:
+      - image: nginx
+        name: nginx-notag
+      - image: nginx@sha256:111111111111111111
+        name: nginx-sha256
+      - image: alpine:1.8.0
+        name: init-alpine
+`,
+			expectedOutput: `
+group: apps
+apiVersion: v1
+kind: Deployment
+metadata:
+  name: deploy1
+spec:
+  template:
+    spec:
+      containers:
+      - image: busybox:v3
+        name: nginx-tagged
+      - image: busybox:v3
+        name: nginx-latest
+      - image: foobar:1
+        name: replaced-with-digest
+      - image: postgres:1.8.0
+        name: postgresdb
+      initContainers:
+      - image: busybox:v3
+        name: nginx-notag
+      - image: busybox:v3
+        name: nginx-sha256
+      - image: alpine:1.8.0
+        name: init-alpine
+`,
+			filter: Filter{
+				ImageTag: types.Image{
+					Name:    "nginx",
+					NewName: "busybox",
+					NewTag:  "v3",
+				},
+			},
+			fsSlice: []types.FieldSpec{
+				{
+					Path: "spec/template/spec/containers[]/image",
+				},
+				{
+					Path: "spec/template/spec/initContainers[]/image",
+				},
+			},
+			setValueCallback: setValueCallbackStub,
+			expectedSetValueArgs: []setValueArg{
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx:1.7.9",
+				},
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx:latest",
+				},
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx",
+				},
+				{
+					Value:     "busybox:v3",
+					PrevValue: "nginx@sha256:111111111111111111",
+				},
+			},
+		},
 	}
 
 	for tn, tc := range testCases {
+		setValueArgs = nil
 		t.Run(tn, func(t *testing.T) {
 			filter := tc.filter
+			filter.WithMutationTracker(tc.setValueCallback)
 			filter.FsSlice = tc.fsSlice
 			if !assert.Equal(t,
 				strings.TrimSpace(tc.expectedOutput),
 				strings.TrimSpace(filtertest.RunFilter(t, tc.input, filter))) {
 				t.FailNow()
 			}
+			assert.Equal(t, tc.expectedSetValueArgs, setValueArgs)
 		})
 	}
 }

api/filters/imagetag/updater.go

@@ -16,6 +16,7 @@ import (
 type imageTagUpdater struct {
 	Kind            string      `yaml:"kind,omitempty"`
 	ImageTag        types.Image `yaml:"imageTag,omitempty"`
+	trackableSetter filtersutil.TrackableSetter
 }
 
 func (u imageTagUpdater) SetImageValue(rn *yaml.RNode) error {
@@ -40,7 +41,7 @@ func (u imageTagUpdater) SetImageValue(rn *yaml.RNode) error {
 		tag = "@" + u.ImageTag.Digest
 	}
 
-	return filtersutil.SetScalar(name + tag)(rn)
+	return u.trackableSetter.SetScalar(name + tag)(rn)
 }
 
 func (u imageTagUpdater) Filter(rn *yaml.RNode) (*yaml.RNode, error) {